TWI898441B - Remote plasma based deposition of silicon carbide films using silicon-containing and carbon-containing precursors - Google Patents

Abstract

A doped or undoped silicon carbide film can be deposited using a remote plasma chemical vapor deposition (CVD) technique. One or more silicon-containing precursors are provided to a reaction chamber. Radical species, such as hydrogen radical species, are provided in a substantially low energy state or ground state and interact with the one or more silicon-containing precursors to deposit the silicon carbide film. A carbon-containing precursor may be flowed with the one or more silicon-containing precursors, where the carbon-containing precursor has one or more carbon-to-carbon double bonds or triple bonds and each silicon-containing precursor is a silane-based precursor with at least a silicon atom having two or more hydrogen atoms bonded to the silicon atom.

Description

Remote plasma-based silicon carbide film deposition using silicon- and carbon-containing precursors

Embodiments herein relate to remote plasma-based silicon carbide film deposition using silicon-containing and carbon-containing precursors.

Silicon carbide (SiC) thin films possess unique physical, chemical, and mechanical properties and are used in a variety of applications, particularly in integrated circuits. Types of SiC thin films include oxygen-doped silicon carbide (also known as silicon oxycarbide), nitrogen-doped silicon carbide (also known as silicon carbonitride), oxygen- and nitrogen-doped silicon carbide (also known as silicon oxycarbide), and undoped silicon carbide.

The prior art description provided here is intended to generally introduce the background of the present invention. The achievements of the inventors named in this application within the scope of the prior art section, as well as any embodiments that do not qualify as prior art in the specification at the time of filing, are not intended or implied to be admitted as prior art against the present invention.

A method for depositing a silicon carbide film on a substrate is provided. The method includes providing a substrate in a reaction chamber; flowing a silicon-containing precursor into the reaction chamber and toward the substrate; and flowing a co-reactant into the reaction chamber along with the silicon-containing precursor. The silicon-containing precursor has at least two hydrogen atoms bonded to silicon atoms, and the co-reactant is a hydrocarbon molecule. The method further includes generating hydrogen radicals from a hydrogen source gas in a remote plasma source, the hydrogen radicals being generated upstream of the silicon-containing precursor and the co-reactant; and introducing the hydrogen radicals into the reaction chamber and toward the substrate, wherein the hydrogen radicals are in a ground state to react with the silicon-containing precursor and the co-reactant to form a doped or undoped silicon carbide film on the substrate.

In some embodiments, all or substantially all of the hydrogen radicals in the environment adjacent to the substrate are ground state hydrogen radicals. In some embodiments, the hydrocarbon molecule has one or more carbon-carbon double or triple bonds. The hydrocarbon molecule may include propylene, butene, pentene, butadiene, pentadiene, hexadiene, heptadiene, toluene, benzene, acetylene, propyne, butyne, pentyne, or hexyne. In some embodiments, the silicon-containing precursor includes silane, disilane, trisilane, methylsilane, or dimethylsilane. In some embodiments, the silicon carbide film, whether doped or undoped, has no C-C bonds or substantially no C-C bonds. In some embodiments, the method further includes providing a nitriding agent in the remote plasma source along with the hydrogen source gas, wherein radicals of the nitriding agent are generated in the remote plasma source; and introducing the radicals of the nitriding agent and the radicals of hydrogen into the reaction chamber and toward the substrate, wherein the nitriding agent and the radicals of hydrogen react with the silicon-containing precursor and the co-reactant to form a silicon carbonitride (SiCN) film. The SiCN film has no or substantially no C-C bonds and no or substantially no C-N bonds. In some embodiments, the method further includes providing an oxidant in the remote plasma source along with the hydrogen source gas, wherein free radicals of the oxidant are generated in the remote plasma source; and introducing the free radicals of the oxidant and the free radicals of hydrogen into the reaction chamber and toward the substrate, wherein the oxidant and the free radicals of hydrogen react with the silicon-containing precursor and the co-reactant to form a silicon oxycarbide (SiCO) film. The SiCO film has no or substantially no C-C bonds and no or substantially no C-O bonds. In some embodiments, the silicon carbide film, whether doped or undoped, has a conformality of at least 75%. In some embodiments, the silicon-containing precursor lacks (i) C-O bonds and (ii) C-N bonds.

These and other implementations are further described below with reference to the drawings.

In this disclosure, the terms "semiconductor wafer,""wafer,""substrate,""wafersubstrate," and "partially processed integrated circuit" are used interchangeably. Those skilled in the art will understand that the term "partially processed integrated circuit" can refer to a silicon wafer during any of many stages of integrated circuit processing. Wafers or substrates used in the semiconductor device industry typically have a diameter of 200 mm, or 300 mm, or 450 mm. The following embodiments illustrate the assumption that the present disclosure is implemented on a wafer. However, the present disclosure is not so limited. The workpiece can be of various shapes, sizes, and materials. In addition to semiconductor wafers, other workpieces that can utilize the present disclosure include various items, such as printed circuit boards. Introduction

The fabrication of semiconductor devices typically involves depositing one or more thin films onto a substrate during an integrated circuit fabrication process. In certain aspects of the fabrication process, various types of thin films, such as silicon carbide, silicon oxycarbide, silicon carbonitride, and silicon oxycarbonitride, are deposited using atomic layer deposition (ALD), chemical vapor deposition (CVD), plasma-assisted chemical vapor deposition (PECVD), or any other suitable deposition method. As used herein, the term silicon carbide includes undoped and doped silicon carbide, such as oxygen-doped silicon carbide (SiCO), nitrogen-doped silicon carbide (SiCN), and nitrogen- and oxygen-doped silicon carbide (SiOCN). In many cases, the doped silicon carbide has up to about 50 atomic % of dopant atoms, whether oxygen, nitrogen, or atoms of another element. The doping level provides the desired film properties.

Precursor molecules used to deposit silicon carbide may include silicon-containing molecules having silicon-hydrogen (Si–H) and/or silicon-silicon (Si–Si) bonds, as well as silicon-carbon (Si–C) bonds. Precursor molecules used to deposit silicon oxycarbide may include silicon-containing molecules having silicon-hydrogen (Si–H) bonds and/or silicon-silicon (Si–Si) bonds, as well as silicon-oxygen (Si–O) bonds and/or silicon-carbon (Si–C) bonds. Precursor molecules used to deposit silicon carbonitrides include silicon-containing molecules having silicon-hydrogen (Si–H) bonds and/or silicon-silicon (Si–Si) bonds, as well as silicon-nitrogen (Si–N) bonds and/or silicon-carbon (Si–C) bonds. Precursor molecules used to deposit silicon oxycarbonitrides include silicon-containing molecules having silicon-hydrogen (Si–H) bonds and/or silicon-silicon (Si–Si) bonds, as well as silicon-nitrogen (Si–N) bonds, silicon-oxygen (Si–O) bonds, and/or silicon-carbon (Si–C) bonds. Current PECVD processes can use in-situ plasma treatment, in which the plasma is provided directly in the vicinity of the substrate.

We have discovered that depositing high-quality silicon carbide films can present certain challenges, such as providing films with excellent step coverage, low dielectric constant, high breakdown voltage, low leakage current, high porosity, and/or covering bare metal surfaces without oxidizing the metal surfaces.

While the present invention is not bound by any particular theory, it is believed that the plasma conditions in a typical PECVD process can fragment silicon-containing precursor molecules in a manner that produces undesirable effects. For example, PECVD may break Si-O and/or Si-C bonds in the precursor molecules, generating highly reactive free radicals or other fragment types with high viscosity coefficients. The resulting fragments of the doped silicon carbide film may contain silicon, carbon, and/or oxygen atoms with "dangling bonds," meaning that the silicon, carbon, and/or oxygen atoms have reactive, unpaired valence electrons. The high viscosity of precursor molecules and their fragments can deposit silicon carbide films with poor step coverage, as reactive precursor fragments can disproportionately adhere to the sidewalls and upper regions of other structures in recessed features.

Dangling bonds can generate silanol groups (Si–OH) in deposited silicon oxycarbide or silicon oxycarbonitride films. Dangling bonds can also generate silanolamine groups (Si-NH ₂ ) in deposited silicon carbonitride films. Due to these functional groups, the films may have an undesirably high dielectric constant. Direct plasma conditions can also negatively impact film quality, as they tend to extract carbon from the deposited films.

Furthermore, dangling bonds can lead to a higher number of silicon-hydrogen (Si–H) bonds in the deposited silicon carbide film. Under direct plasma deposition conditions, Si–C rupture bonds can be replaced by Si–H bonds. The presence of Si–H bonds in silicon carbide films can result in films with undesirable electrical properties. For example, because Si–H bonds provide leakage paths for electrons, their presence can reduce breakdown voltage and potentially increase leakage current.

Furthermore, dangling bonds can lead to uncontrolled chemical or morphological structures in silicon carbide films. In some cases, these structures are dense fragments with low or no porosity, resulting in films with unacceptably high dielectric constants. The lack of porosity can be caused by direct plasma conditions breaking Si–C and/or Si–O bonds in the cyclosiloxane, which otherwise provide porosity in ultra-low-k dielectric materials.

Because the energy used to disrupt the precursor molecules can be low-frequency, generating a large number of ion bombardments at the surface, the direct plasma conditions sometimes used in PECVD can result in directionality in the deposition. Directional deposition can also result in deposited silicon carbide films with poor step coverage. A direct plasma is a plasma (with moderate concentrations of electrons and positive ions) that resides near the substrate surface during deposition, sometimes separated from it by only a plasma sheath.

Typical PECVD processes are sometimes not suitable for depositing silicon carbide films on exposed copper or other metal surfaces because these processes may oxidize the metal. PECVD processes may use oxidants such as oxygen (O ₂ ), ozone (O ₃ ), carbon dioxide (CO ₂ ), or other oxidizing species to form silicon oxycarbide films. The environment on the substrate surface during deposition is

FIG1A shows a cross-section of an exemplary silicon carbide film deposited on a substrate. Silicon carbide film 101 can be formed under process conditions that create a relatively mild environment adjacent to substrate 100. Substrate 100 can be any wafer, semiconductor wafer, partially processed integrated circuit, printed circuit board, display screen, or other suitable workpiece. The process used to deposit silicon carbide film 101 can involve one or more silicon-containing precursors having one or more Si-H bonds and/or one or more Si-Si bonds. Depending on the type of doped structure to be produced, the one or more silicon-containing precursors can optionally include other bonds, such as Si-C bonds, Si-O bonds, and/or Si-N bonds.

Figures 1B-1E illustrate certain applications using silicon carbide films. In certain embodiments, the silicon-containing precursor may include a silicon-oxygen-containing precursor, a silicon-nitrogen-containing precursor, and/or a silicon-carbon-containing precursor. The silicon-oxygen-containing precursor may include one or more Si-O bonds, the silicon-nitrogen-containing precursor may include one or more Si-N bonds, and the silicon-carbon-containing precursor may include one or more Si-C bonds. In certain embodiments, for example, the silicon-containing precursor may include a single reactant A having Si-O and Si-C bonds, or Si-N and Si-C bonds. In certain embodiments, the silicon-containing precursor may include reactant B having a Si-O bond or a Si-N bond and reactant C having a Si-C bond. It should be understood that any number of suitable reactants may be used within the scope of the present invention. The chemical structures of exemplary silicon-containing precursors are discussed in further detail below.

The silicon-containing precursor comprises one or more Si-H bonds and/or one or more Si-Si bonds. However, it should be understood that the additional silicon-containing precursor need not comprise Si-H or Si-Si bonds. Such additional silicon-containing precursors may be provided simultaneously with the silicon-containing precursor having one or more Si-H and/or Si-Si bonds. During the deposition process, the Si-H bonds and/or Si-Si bonds are broken and serve as reaction sites for forming bonds between the silicon-containing precursor or other precursors in the deposited silicon carbide film 101. The broken bonds may also serve as sites for crosslinking during deposition or during subsequent heat treatment. The bonds and crosslinks at the reaction sites may together form the main backbone or matrix in the resulting silicon carbide film 101.

In some embodiments, process conditions can preserve or substantially preserve Si-C bonds and, if present, Si-O and Si-N bonds in the deposited layer of silicon carbide film 101. Thus, reaction conditions adjacent to substrate 100 provide for the selective breaking of Si-H and/or Si-Si bonds, such as extracting hydrogen from broken Si-H bonds, but the reaction conditions do not extract oxygen from Si-O bonds, nitrogen from Si-N bonds, or carbon from Si-C bonds. However, the introduction of a co-reactant (e.g., oxygen) can extract carbon from Si-C bonds. It should be understood that other reaction mechanisms, including kinetically less favorable reaction mechanisms such as substitution reactions, may occur in the environment adjacent to the substrate surface. Generally speaking, the reaction conditions described above exist at the exposed surface of the substrate 100 (the surface where the silicon carbide film 101 is deposited). They may also exist at a distance above the substrate 100, for example, from about 0.5 microns to about 150 mm above the substrate 100. In practice, activation of the precursor may occur in the vapor phase at a substantial distance above the substrate 100. Typically, the reaction conditions are uniform or substantially uniform across the entire exposed surface of the substrate 100, but some applications may tolerate some degree of variation.

In addition to the silicon-containing precursor, the environment adjacent to the workpiece (e.g., substrate 100) may include one or more radical species, preferably radical species in a substantially low energy state. An example of such species includes hydrogen radicals (i.e., atomic hydrogen radicals). In some embodiments, all, or substantially all, or a substantial portion of the atomic hydrogen radicals may be in the ground state, for example, at least about 90% or 95% of the atomic hydrogen radicals adjacent to the workpiece are in the ground state. In some embodiments, the source gas is provided in a carrier gas (e.g., helium). For example, the hydrogen gas may be provided in a helium carrier gas at a hydrogen concentration of about 1-10%. The pressure, fraction, and other process conditions of the carrier gas (e.g., helium) are selected so that the hydrogen atoms encounter the substrate 100 in the form of radicals in a low energy state without recombination.

As described elsewhere, hydrogen gas can be supplied to a remote plasma source to generate hydrogen atomic radicals. The remote plasma source can be positioned upstream of the substrate surface and the environment adjacent to the substrate surface. Once generated, the hydrogen atomic radicals can be in an excited energy state. For example, hydrogen in an excited energy state can have an energy of at least 10.2 eV (a first excited state). The excited hydrogen atomic radicals can cause non-selective decomposition of silicon-containing precursors. For example, the excited hydrogen atomic radicals can easily break Si-H, Si-Si, Si-N, Si-O, and Si-C bonds, which can change the composition, or physical or electrical properties of the silicon carbide film 101. In some embodiments, when excited hydrogen radicals lose their energy or relax, they may become hydrogen radicals in a substantially low-energy state or a ground state. Hydrogen radicals in the substantially low-energy state or ground state may selectively break Si-H and Si-Si bonds while substantially preserving Si-O, Si-N, and Si-C bonds. In some embodiments, process conditions may be provided to cause excited hydrogen radicals to lose energy or relax to form hydrogen radicals in the substantially low-energy state or ground state. For example, the remote plasma source or related components may be designed so that the residence time of the hydrogen radicals diffusing from the remote plasma source to the substrate 100 is greater than the energy relaxation time of the excited hydrogen radicals. The energy relaxation time of the excited hydrogen radical may be approximately equal to or less than approximately 1×10 ⁻³ seconds.

A substantial portion of the hydrogen atomic radicals being in the ground state can be achieved by various techniques. Certain equipment, such as the equipment described below, is designed to achieve this state. Equipment characteristics and process control characteristics can be tested and tuned to produce a mild state in which a substantial portion of the hydrogen atomic radicals are in the ground state. For example, the equipment can be operated and tested for charged particles downstream of the plasma source (i.e., near the substrate 100). The process and equipment can be tuned until substantially no charged species are present near the substrate 100. In addition, the equipment and process characteristics can be tuned to a configuration that begins forming the silicon carbide film 101 from a standard silicon-containing precursor. Relatively mild conditions are selected to support the deposition of these films.

Other examples of free radical species include oxygen-containing species such as elemental oxygen radicals (atomic or diatomic), nitrogen-containing species (e.g., elemental nitrogen radicals) (atomic or diatomic), and N-H-containing radicals (e.g., ammonia radicals), wherein nitrogen is optionally incorporated into the film. Examples of N-H-containing radicals include, but are not limited to, radicals of methylamine, dimethylamine, and aniline. The above-mentioned free radical species can be generated from a source gas comprising hydrogen, nitrogen, an N-H-containing species, or a mixture thereof. In some embodiments, substantially all or a substantial portion of the atoms of the deposited film are provided by precursor molecules. In such cases, the low-energy free radicals used to drive the deposition reaction can be hydrogen or other species that do not substantially contribute to the quality of the deposited film. In some embodiments, as discussed in more detail below, radical species may be generated by a remote plasma source. In some embodiments, some radicals or ions in higher energy states may potentially exist near the wafer plane.

In some embodiments, process conditions utilize radical species in substantially low energy states sufficient to break Si-H and/or Si-Si bonds while substantially preserving Si-O, Si-N, and Si-C bonds. These process conditions may not have a significant number of ions, electrons, or radical species in high energy states (e.g., energy states above the ground state). In some embodiments, the ion concentration in the region adjacent to the film is no greater than about 10 ⁷ /cm ³ . The presence of significant numbers of ions or high-energy radicals tends to break Si-O, Si-N, and Si-C bonds, which may result in a film with undesirable electrical properties (e.g., high dielectric constant and/or low breakdown voltage) and poor conformality. It is generally believed that an overly reactive environment produces reactive precursor fragments with high viscosity coefficients (representing the tendency to chemically or physically adhere to the sidewalls of the workpiece), which leads to poor conformal properties.

The silicon-containing precursor is typically transported to an environment adjacent to the substrate 100 using other species, particularly a carrier gas. In some embodiments, the silicon-containing precursor is present along with radical species and other species, including other reactive species and/or a carrier gas. In some embodiments, the silicon-containing precursor may be introduced as a mixture. Upstream of the deposition reaction surface, the silicon-containing precursor may be mixed with an inert carrier gas. Exemplary inert carrier gases include, but are not limited to, argon (Ar) and helium (He). In addition, the silicon-containing precursor may be introduced as a mixture of primary and secondary species, wherein the secondary species includes certain elements or structural features (such as ring structures, cage structures, unsaturated bonds, etc.) that are present in relatively low concentrations in the silicon carbide film 101. However, it should be understood that the minor species may not significantly affect the composition and structural characteristics of the silicon carbide film 101. The multiple precursors may be present in equimolar amounts or in relatively similar proportions suitable for forming the primary backbone or matrix in the resulting silicon carbide film 101. In other embodiments, the relative amounts of the different precursors deviate substantially from equimolar concentrations by volume.

In some embodiments, the one or more silicon-containing precursors provide substantially all of the mass of the silicon carbide film 101, with only a small amount of hydrogen or other elements from the remote plasma providing less than about 5 atomic percent or less than about 2 atomic percent of the film mass. In some embodiments, only radical species and the one or more silicon-containing precursors contribute to the composition of the deposited silicon carbide film 101. In other embodiments, the deposition reaction includes co-reactants other than the one or more silicon-containing precursors and the radical species, which may or may not contribute to the composition of the deposited silicon carbide film 101. Examples of such co-reactants include carbon dioxide (CO ₂ ), carbon monoxide (CO), water (H ₂ O), methanol (CH ₃ OH), oxygen (O ₂ ), ozone (O ₃ ), nitrogen (N ₂ ), nitrous oxide (N ₂ O), ammonia (NH ₃ ), diazene (N ₂ H ₂ ), methane (CH ₄ ), ethane (C ₂ H ₆ ), acetylene (C ₂ H ₂ ), ethylene (C ₂ H ₄ ), diborane (B ₂ H ₆ ), and combinations thereof. Such materials can be used as nitriding agents, oxidizing agents, reactants, etc. In some cases, the carbon content of the deposited film can be tuned by removing or adding some of the carbon provided by the silicon-containing precursor. In certain embodiments using a non-hydrogen co-reactant, the co-reactant is introduced into the reaction chamber through the same flow path as the silicon-containing precursor, such as a path that includes a gas outlet or showerhead and is generally not directly exposed to the plasma. In certain embodiments, oxygen and/or carbon dioxide are introduced with the precursor during deposition to modify the composition of the silicon carbide film 101 by removing carbon from the film or precursor. In certain embodiments using a non-hydrogen co-reactant, the co-reactant is introduced into the reaction chamber through the same flow path as hydrogen, so that at least a portion of the co-reactant is converted into radicals and/or ions. In these embodiments, both hydrogen radicals and co-reactant radicals react with the silicon-containing precursor(s) to produce the deposited silicon carbide film 101 .

In certain embodiments where a co-reactant is used and introduced into the reaction chamber along with a species to be converted into free radicals (e.g., hydrogen), the co-reactant is provided to the reaction chamber in a relatively small amount relative to the other gases in the reaction chamber, including the source of free radicals (e.g., hydrogen) and any carrier gas(es) (e.g., helium). For example, the co-reactant may be present in the process gas at a concentration of about 0.05 mass % or less, 0.01 mass % or less, or 0.001 mass % or less. For example, the reactant mixture (entering the plasma source) may be about 10-20 liters per minute (L/m) of He, about 200-500 standard cubic centimeters per minute (sccm) of _H2 , and about 1-10 sccm of oxygen. However, it should be understood that in certain embodiments, the co-reactant may be present in the process gas at a concentration of about 0.05 mass % or more, or 1 mass % or more, or 20 mass % or more. When the co-reactant is introduced into the reaction chamber with the silicon-containing precursor (e.g., via a gas outlet or showerhead), it may be present at a higher concentration, such as about 2 mass % or less, or about 0.1 mass % or less. When the co-reactant is a relatively weak reactant (e.g., a weak oxidant such as carbon dioxide), it may be present at even higher concentrations (e.g., about 10 mass % or less, or about 4 mass % or less). When the co-reactant is an additive or additional precursor, it may be present at even higher concentrations (e.g., about 10 mass % or more, or about 20 mass % or more).

The temperature of the environment adjacent to substrate 100 can be any suitable temperature that promotes the deposition reaction, but is sometimes limited by the application of the device containing silicon carbide film 101. In some embodiments, the temperature of the environment adjacent to substrate 100 during deposition of silicon carbide film 101 can be largely controlled by the temperature of the pedestal on which substrate 100 is supported. In some embodiments, the operating temperature can be between about 50°C and about 500°C. For example, in many integrated circuit applications, the operating temperature can be between about 250°C and about 400°C. In some embodiments, increasing the temperature can result in increased cross-linking on the substrate surface.

The pressure in the environment adjacent to the substrate 100 can be any suitable pressure for generating reactive radicals in the reaction chamber. In some embodiments, the pressure can be approximately 35 Torr or less. For example, in embodiments using microwave-generated plasma, the pressure can be between approximately 10 Torr and approximately 20 Torr. In other examples, such as in embodiments using radio frequency (RF)-generated plasma, the pressure can be less than approximately 5 Torr or between approximately 0.2 Torr and approximately 5 Torr.

The environment adjacent to the substrate 100 facilitates the deposition of a silicon carbide film 101 on the substrate 100 via remote plasma CVD. A source gas is supplied to the remote plasma source, and power is provided to the remote plasma source. The power dissociates the source gas and generates ions and radicals in an excited energy state. After excitation, the radicals in the excited energy state relax into radicals in a substantially lower energy state or into a ground state, such as a ground state hydrogen radical. The hydrogen radicals in the relaxed energy state can selectively break bonds in the silicon-containing precursor. The hydrogen radical in the relaxed energy state can be used to selectively break the bond in the co-reactant or other precursor, thereby activating the co-reactant or other precursor.

Silicon carbide films are frequently used in semiconductor devices. For example, doped or undoped silicon carbide films can be used as metal diffusion barriers, etch stop layers, hard masks, gate spacers for source and drain implants, capping barriers for magnetoresistive random access memory (MRAM) or resistive random access memory (RRAM), and airtight diffusion barriers in air gaps. Figures 1B–1E show cross-sections of structures incorporating silicon carbide films in various applications. Figure 1B shows a vertical thin film of silicon carbide conformally deposited on a feature on a substrate. Figure 1C shows a vertical structure of silicon carbide on the sidewalls of a transistor gate electrode structure. Figure 1D shows a vertical structure of silicon carbide on the exposed sidewalls of a copper line in an air-gapped metallization layer. Figure 1E shows a silicon carbide pore filler in a porous dielectric material. Each of these applications is discussed in more detail below. Chemical Structure of Precursor

As discussed, the precursor used in forming the silicon carbide film may include a silicon-containing precursor, wherein at least some of the silicon-containing precursor has at least one Si—H and/or at least one Si—Si bond. In some embodiments, the silicon-containing precursor has at least one hydrogen atom per silicon atom. Thus, for example, a precursor having one silicon atom has at most one hydrogen atom bonded to that silicon atom; a precursor having two silicon atoms has one hydrogen atom bonded to one silicon atom and optionally has another hydrogen atom bonded to a second silicon atom; a precursor having three silicon atoms has one hydrogen atom bonded to one silicon atom and optionally has one or two hydrogen atoms bonded to one or both of the remaining silicon atoms; and so on. However, in certain embodiments, the silicon-containing precursor has two or more hydrogen atoms bonded to one silicon atom or to each silicon atom. Furthermore, the silicon-containing precursor may include at least one Si—O bond, at least one Si—N bond, and/or at least one Si—C bond. While any number of suitable precursors may be used in forming silicon carbide films, at least some of the precursors will include silicon-containing precursors having at least one Si-H bond or Si-Si bond, and optionally at least one Si-O bond, Si-N bond, and/or Si-C bond. In various embodiments, the silicon-containing precursor(s) do not include O-C or N-C bonds; for example, the precursor(s) do not include alkoxy (-OR), where R is an organic group (e.g., a _alkyl group), or amine ( _-NR1R2 ), where _R1 and _R2 are independently hydrogen or an organic group. It is believed that these groups impart a high viscosity to the precursor or fragment in which they reside.

In some embodiments, a portion of the carbon provided in the silicon carbide film can come from one or more hydrocarbon functional moieties on the silicon-containing precursor. Such functional moieties can come from alkyl groups, alkenyl groups, alkynyl groups, aryl groups, etc. In some embodiments, the hydrocarbon group has a single carbon atom to minimize steric hindrance of Si-H and/or Si-Si bonds that interrupt the reaction during deposition. However, the precursor is not limited to a single carbon group; a higher number of carbon atoms, such as 2, 3, 4, 5, or 6 carbon atoms, can be used. In some embodiments, the hydrocarbon group is linear. In some embodiments, the hydrocarbon group is cyclic.

In some embodiments, a portion of the carbon provided in the silicon carbide film may be derived from one or more hydrocarbon molecules in the silicon-containing precursor. These hydrocarbon molecules may comprise carbon-carbon chains, wherein a number of carbon atoms may be used, for example, 2, 3, 4, 5, 6, or 7 carbon atoms. In some embodiments, the hydrocarbon molecules comprise one or more carbon double bonds and/or carbon triple bonds.

In certain embodiments, the silicon-containing precursor falls into one chemical class. It should be understood that other chemical classes of silicon-containing precursors may be used and the silicon-containing precursors are not limited to the chemical classes discussed below.

In some embodiments, the silicon-containing precursor may be a siloxane. In some embodiments, the siloxane may be cyclic. Cyclosiloxanes may include cyclotetrasiloxanes, such as 2,4,6,8-tetramethylcyclotetrasiloxane (TMCTS), decamethylcyclotetrasiloxane (OMCTS), and heptamethylcyclotetrasiloxane (HMCTS). Other cyclosiloxanes may also include (but are not limited to) cyclotrisiloxane and cyclopentasiloxane. An embodiment using cyclosiloxanes is a ring structure, which can introduce porosity into the silicon carbide film and the size of the pores corresponds to the radius of the ring. For example, the ring of cyclotetrasiloxane may have a radius of approximately 6.7 Å.

In some embodiments, the siloxane can have a three-dimensional or cage-like structure. Figure 2 shows an example of a representative cage-like siloxane precursor. A cage-like siloxane has silicon atoms bridged to each other by oxygen atoms to form a polyhedron or any 3-D structure. An example of a cage-like siloxane precursor molecule is a silsesquioxane. The cage-like siloxane structure is described in more detail in co-owned U.S. Patent No. 6,576,345 to Cleemput et al., the entire contents of which are incorporated herein by reference for all purposes. Similar to cyclosiloxanes, cage-like siloxanes can introduce porosity into the silicon carbide film. In some embodiments, the porosity is on the scale of mesopores.

In some embodiments, the siloxane may be linear. Examples of suitable linear siloxanes include, but are not limited to, disiloxanes (e.g., pentamethyldisiloxane (PMDSO) and tetramethyldisiloxane (TMDSO)), and trisiloxanes (e.g., hexamethyltrisiloxane and heptamethyltrisiloxane).

In some embodiments, the silicon-containing precursor may be an alkylsilane or other alkyl-substituted silane. Alkylsilanes comprise a central silicon atom, one or more alkyl groups bonded to the central silicon atom, and one or more hydrogen atoms bonded to the central silicon atom. In some embodiments, one or more of the alkyl groups comprises 1-5 carbon atoms. The alkyl groups may be saturated or unsaturated (e.g., alkenes (e.g., ethylene), alkynes, and aromatic groups). Examples include, but are not limited to, trimethylsilane (3MS), triethylsilane, pentamethyldisilazane (( _CH3 ) _2Si - _CH2 -Si( _CH3 ) ₃ ), and dimethylsilane (2MS).

In some embodiments, the silicon-containing precursor may be an alkoxysilane. However, it should be understood that in some embodiments, the silicon-containing precursor is not an alkoxysilane to avoid the presence of alkoxy groups. Alkoxysilanes comprise a central silicon atom, one or more alkoxy groups bonded to the central silicon atom, and one or more hydrogen atoms bonded to the central silicon atom. Examples include, but are not limited to, trimethoxysilane (TMOS), dimethoxysilane (DMOS), methoxysilane (MOS), methyldimethoxysilane (MDMOS), diethoxymethylsilane (DEMS), dimethylethoxysilane (DMES), and dimethylmethoxysilane (DMMOS).

Disilane, trisilane, or other higher silanes may be used in place of the monosilane. An example of such a disilane from the class of alkylsilanes is hexamethyldisilane (HMDS). Another example of such a disilane from the class of alkylsilanes may include pentamethyldisilane (PMDS). Other types of alkylsilanes may include alkylcarbosilanes, which may have a branched polymeric structure with a carbon bonded to a silicon atom and an alkyl group bonded to a silicon atom. Examples include dimethyltrimethylsilylmethane (DTMSM) and bis-dimethylsilylethane (BDMSE). In certain embodiments, one of the plurality of silicon atoms may have a carbon- or alkyl-containing group attached thereto, and one of the plurality of silicon atoms may have a hydrogen atom attached thereto.

In some embodiments, the silicon-containing precursor may be a nitrogen-containing compound, such as a silicon-nitrogen hydride (e.g., silazane). Generally, such compounds contain carbon, but the carbon is bonded only to silicon atoms, not to nitrogen atoms. In some embodiments, the nitrogen-containing compound does not have any carbon-nitrogen bonds. In some embodiments, the nitrogen-containing compound does not have any amine functional groups (-C- _NR1R2 ), where _R1 and _R2 are the same or different groups _, such as a hydrogen atom and a alkyl group (e.g., an alkyl group, an alkenyl group, or an alkynyl group). Examples of suitable silicon-nitrogen precursors include various silazanes, such as cyclic or linear silazanes containing one or more hydrocarbon functional groups bonded to one or more silicon atoms and one or more hydrogen atoms bonded to one or more silicon atoms. Examples of silazanes include methyl-substituted disilazanes and trisilazanes, such as tetramethyldisilazane and hexamethyltrisilazane.

During silicon carbide deposition, multiple silicon-containing precursors may be present in the process gas. For example, siloxanes and alkylsilanes may be used together, or siloxanes and alkoxysilanes may be used together. The relative proportions of the individual precursors can be selected based on the chemical structure of the selected precursors and the application of the resulting silicon carbide film. For example, the molar percentage of siloxane may be greater than the molar percentage of silane to produce a porous film, as discussed in more detail below.

For the deposition of oxygen-doped silicon carbide films, examples of suitable precursors include cyclosiloxanes, such as cyclotetrasiloxanes (e.g., heptamethylcyclotetrasiloxane (HMCTS) and tetramethylcyclotetrasiloxane). Other cyclosiloxanes may include, but are not limited to, cyclotrisiloxane and cyclopentasiloxane. Other examples of suitable precursors for the deposition of oxygen-doped silicon carbide films include linear siloxanes, such as, but not limited to, disiloxanes, such as pentamethyldisiloxane (PMDSO), tetramethyldisiloxane (TMDSO), hexamethyltrisiloxane, and heptamethyltrisiloxane.

For the deposition of undoped silicon carbide films, examples of suitable precursors may include monosilanes substituted with one or more alkane, alkene, and/or alkyne groups containing, for example, 1-5 carbon atoms. Examples include, but are not limited to, trimethylsilane (3MS), dimethylsilane (2MS), triethylsilane (TES), and pentamethyldisilane. In addition, disilane, trisilane, or other higher silanes may be used in place of the monosilane. Examples of disilanes include hexamethyldisilane (HMDS) and pentamethyldisilane (PMDS). Other types of alkylsilanes may include alkylcarbosilanes. Examples include dimethyltrimethylsilylmethane (DTMSM) and bis-dimethylsilylethane (BDMSE).

For the deposition of nitrogen-doped silicon carbide films, examples of suitable precursors include silazanes, such as alkyldisilazanes, and compounds containing an amine group (-NH2) and an alkyl group, each bonded to one or more silicon atoms. Alkyldisilazanes contain a silazane and an alkyl group bonded to two silicon atoms. One example includes 1,1,3,3-tetramethyldisilazane (TMDSN).

As described, silicon-containing precursors are selected to provide highly conformal silicon carbide films. It is generally believed that silicon-containing precursors with low viscosity coefficients are capable of producing highly conformal films. The term "viscosity coefficient" is used to describe the ratio of the number of adsorbed species (such as fragments or molecules) adsorbed/adhered to a surface to the total number of species impinging on the surface during the same time period. The symbol Sc is sometimes used to refer to the viscosity coefficient. The value of Sc ranges from 0 (meaning no species adheres) to 1 (meaning all impinging species adhere). Various factors that affect the viscosity coefficient include the type of impinging species, the surface temperature, the surface step coverage, the structural details of the surface, and the kinetic energy of the impinging species. Some species are inherently more "sticky" than others, making them more likely to adhere to a surface each time they impact the surface. Such stickier species have a larger viscosity coefficient (when all other factors are equal), and species with a larger viscosity coefficient are more likely to adhere near the entrance of a recessed feature than less sticky species with a lower viscosity coefficient. In some cases, the viscosity coefficient of the precursor (under relevant deposition conditions) can be about 0.05 or less, such as about 0.001 or less. Equipment

One aspect of the present invention is an apparatus configured to perform the methods described herein. Suitable apparatus includes hardware for performing process operations and a system controller having instructions for controlling the process operations in accordance with the present invention. In certain embodiments, the apparatus for performing the process operations includes a remote plasma source. A remote plasma source provides milder reaction conditions than a direct plasma. Examples of suitable remote plasma apparatus are described in U.S. Patent Application No. 14/062,648, filed October 24, 2013, which is incorporated herein by reference in its entirety for all purposes.

FIG3 is a schematic diagram of a remote plasma apparatus according to some embodiments. The apparatus 300 includes a reaction chamber 310 having a showerhead 320. In the reaction chamber 310, a substrate 330 is seated on a table or base 335. In some embodiments, the base 335 may be provided with a heating/cooling element. A controller 340 may be connected to a plurality of components of the apparatus 300 to control the operation of the apparatus 300. For example, the controller 340 may include instructions for controlling process conditions for the operation of the apparatus 300, such as temperature process conditions and/or pressure process conditions. In some embodiments, the controller 340 may include instructions for controlling the flow rates of precursor gases, co-reactant gases, source gases, and carrier gases. Controller 340 may include instructions for varying the flow rate of the co-reactant gas over time. Additionally or alternatively, controller 340 may include instructions for varying the flow rate of the precursor gas over time. A more detailed description of controller 340 is provided below.

During operation, a gas or gas mixture is introduced into the reaction chamber 310 via one or more gas inlets coupled to the reaction chamber 310. In some embodiments, two or more gas inlets are coupled to the reaction chamber 310. A first gas inlet 355 can be coupled to the reaction chamber 310 and connected to a container 350, and a second gas inlet 365 can be coupled to the reaction chamber 310 and connected to the remote plasma source 360. In embodiments including a remote plasma source configuration, the delivery lines used to deliver the precursor and the radical species generated in the remote plasma source are separate. Therefore, the precursor and the radical species do not substantially interact before reaching the substrate 330. It should be understood that in some embodiments, the gas lines may be reversed such that the vessel 350 may provide the precursor gas flow through the second gas inlet 365 , while the remote plasma source 360 may provide the ions and radicals through the first gas inlet 355 .

One or more free radical species may be generated in a remote plasma source 360 and configured to enter the reaction chamber 310 through a second gas inlet 365. Any type of plasma source may be used in the remote plasma source 360 to generate the free radical species. This includes, but is not limited to, capacitively coupled plasma, inductively coupled plasma, microwave plasma, DC plasma, and radio-generated plasma. An example of a capacitively coupled plasma may be a radio frequency (RF) plasma. High frequency plasmas may be configured to operate at frequencies of 13.56 MHz or higher. An example of such a remote plasma source 360 may be the GAMMA® manufactured by Colin Research & Development, Inc. of Fremont, California. Another example of such a remote plasma source 360 may be the Astron® manufactured by MKS Instruments of Wilmington, Massachusetts, which may operate at 440 kHz and may be provided as a subunit latched onto a large-scale apparatus for processing one or more substrates in parallel. In some embodiments, a microwave plasma may be used as the remote plasma source 360, such as in the Astex® also manufactured by MKS Instruments. Microwave plasma may be used to operate at a frequency of 2.45 GHz. The gas provided to the remote plasma source may include hydrogen, nitrogen, oxygen, and other gases mentioned elsewhere herein. In some embodiments, the hydrogen is provided in a carrier gas (e.g., helium). For example, the hydrogen may be provided at a hydrogen concentration of approximately 1–10% in a helium carrier gas.

A precursor may be provided in a container 350 and supplied to the showerhead 320 via a first gas inlet 355. The showerhead 320 distributes the precursor into the reaction chamber 310 toward the substrate 330. The substrate 330 may be positioned below the showerhead 320. It should be understood that the showerhead 320 may have any suitable shape and may have any number and configuration of ports for distributing gas to the substrate 330. The precursor may be supplied to the showerhead 320 and ultimately to the substrate 330 at a controlled flow rate.

One or more radical species formed in the remote plasma source 360 can be carried in a gas phase toward the substrate 330. The one or more radical species can flow through the second gas inlet 365 and into the reaction chamber 310. It should be understood that the second gas inlet 365 need not be across the surface of the substrate 330 as shown in FIG3 . In some embodiments, the second gas inlet 365 can be located directly above the substrate 330 or at other locations. The distance between the remote plasma source 360 and the reaction chamber 310 can be configured to provide mild reaction conditions so that the ionized species generated in the remote plasma source 360 are substantially neutralized, but at least a portion of the radical species in a substantially low energy state remain in the environment adjacent to the substrate 330. These low-energy radical species do not recombine to form stable compounds. The distance between the remote plasma source 360 and the reaction chamber 310 can be a function of the aggressiveness of the plasma (e.g., determined in part by the source RF power level), the density of the gas in the plasma (e.g., if there is a high concentration of hydrogen atoms, most of them may recombine to form _H2 before reaching the reaction chamber 310), and other factors. In some embodiments, the distance between the remote plasma source 360 and the reaction chamber 310 can be between about 1 cm and 30 cm, such as about 5 cm or about 15 cm.

In some embodiments, a co-reactant other than a predominantly silicon-containing precursor or hydrogen radical is introduced during the deposition reaction. In some embodiments, the apparatus is configured to introduce the co-reactant via the second gas inlet 365, where the co-reactant is at least partially converted into plasma. In some embodiments, the apparatus introduces the co-reactant via the first gas inlet 355 through the showerhead 320. Examples of co-reactants include oxygen, nitrogen, ammonia, carbon dioxide, carbon monoxide, and the like. The flow rate of the co-reactant can be varied over time to produce a composition gradient in the gradual film.

According to certain other embodiments, FIG4 shows a schematic diagram of an exemplary plasma processing apparatus having a remote plasma source. Plasma processing apparatus 400 includes a remote plasma source 402 separate from a reaction chamber 404. Remote plasma source 402 is fluidically coupled to reaction chamber 404 via a multi-port gas distributor 406, which may also be referred to as a showerhead. Radical species are generated in remote plasma source 402 and supplied to reaction chamber 404. One or more silicon-containing precursors are supplied to reaction chamber 404 downstream of remote plasma source 402 and multi-port gas distributor 406. The one or more silicon-containing precursors react with the radical species in a chemical vapor deposition region 408 of the reaction chamber 404 to deposit a silicon carbide film on the surface of the substrate 412. The chemical vapor deposition region 408 includes an environment adjacent to the surface of the substrate 412.

The substrate 412 is supported on a substrate support or pedestal 414. The pedestal 414 is movable within the reaction chamber 404 to position the substrate 412 within the chemical vapor deposition area 408. In the embodiment shown in FIG4 , the pedestal 414 is shown raising the substrate 412 within the chemical vapor deposition area 408. In some embodiments, the pedestal 414 can also adjust the temperature of the substrate 412. The pedestal 414 can provide some selective control over thermally activated surface reactions on the substrate 412.

FIG4 shows a coil 418 disposed around a remote plasma source 402, wherein the remote plasma source 402 includes an outer wall (e.g., a quartz dome). The coil 418 is electrically coupled to a plasma generator controller 422, which can be used to form and maintain a plasma within a plasma region 424 via inductively coupled plasma generation. In some embodiments, the plasma generator controller 422 can include a power supply for supplying power to the coil 418, wherein the power during plasma generation can be in the range of approximately 1 to 6 kilowatts (kW). In some embodiments, electrodes or antennas used for parallel plate or capacitively coupled plasma generation can be used to generate a continuous supply of free radicals via plasma excitation, rather than using inductively coupled plasma generation. Regardless of the mechanism used to ignite and maintain the plasma within the plasma region 424, free radical species can be continuously generated during film deposition using plasma excitation. In some embodiments, hydrogen radicals are generated under near-steady-state conditions during steady-state film deposition, but may be transient at the beginning and end of film deposition.

When hydrogen or other source gas is supplied to the remote plasma source 402, a supply of hydrogen radicals can be continuously generated within the plasma region 424. Excited hydrogen radicals can be generated within the remote plasma source 402. If not reactivated or re-energized, or recombined with other radicals, the excited hydrogen radicals lose their energy or relax. Consequently, the excited hydrogen radicals can relax to form hydrogen radicals in a substantially low energy state or ground state.

The hydrogen or other source gas may be diluted using one or more additional gases. The one or more additional gases may be supplied to the remote plasma source 402. In some embodiments, the hydrogen or other source gas is mixed with one or more additional gases to form a gas mixture, wherein the one or more additional gases may include a carrier gas. Non-limiting examples of additional gases may include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and nitrogen ( _N2 ). The one or more additional gases may support or stabilize a stable plasma state within the remote plasma source 402 or assist in the ignition or extinction process of a transient plasma. In some embodiments, diluting hydrogen or other source gases with, for example, helium can facilitate higher total pressures without causing concomitant plasma breakdown. In other words, a diluted gas mixture of hydrogen and helium can facilitate higher total gas pressures without increasing the plasma power supplied to the remote plasma source 402. As shown in FIG4 , a source gas supply 426 is fluidly coupled to the remote plasma source 402 to supply hydrogen or source gas. Additionally, an additional gas supply 428 is fluidly coupled to the remote plasma source 402 to supply one or more additional gases. The one or more additional gases may also include the co-reactant gas described above. 4 shows the gas mixture of the source gas and one or more additional gases being introduced through separate gas outlets, it should be understood that the gas mixture can be introduced directly into the remote plasma source 402. That is, a pre-mixed, dilute gas mixture can be supplied to the remote plasma source 402 through a single gas outlet.

Gases (e.g., excited hydrogen and helium radicals, and relaxed gases/radicals) flow from a remote plasma source 402 through a multi-port gas distributor 406 into a reaction chamber 404. The gases within the multi-port gas distributor 406 and the reaction chamber 404 are typically not subjected to continuous plasma excitation. In some embodiments, the multi-port gas distributor 406 includes an ion filter and/or a photon filter. Filtering ions and/or photons can reduce substrate damage, undesired molecular re-excitation, and/or selective cleavage or decomposition of silicon-containing precursors within the reaction chamber 404. The multi-port gas distributor 406 may have a plurality of gas ports 434 to diffuse the gas flow into the reaction chamber 404. In some embodiments, the plurality of gas ports 434 may be spaced apart from one another. In some embodiments, the plurality of gas ports 434 may be arranged as an array of regularly spaced channels or through-holes extending through a plate separating the remote plasma source 402 from the reaction chamber 404. The plurality of gas ports 434 may smoothly disperse and diffuse the radicals exiting the remote plasma source 402 into the reaction chamber 404.

A typical remote plasma source is quite different from a reaction vessel. Therefore, free radical destruction and recombination (e.g., through wall collision events) may significantly reduce the number of reactive species. In contrast, in some embodiments, the size of the plurality of gas ports 434 may be configured based on the mean free path or gas flow residence time under typical processing conditions to facilitate free entry of free radicals into the reaction chamber 404. In some embodiments, the openings of the plurality of gas ports 434 may occupy between about 5% and about 20% of the exposed surface area of the multi-port gas distributor 406. In some embodiments, the plurality of gas ports 434 may each have an axial length to diameter ratio of between about 3:1 and 10:1, or between about 6:1 and 8:1. These aspect ratios can reduce the frequency of wall collisions for radical species passing through the plurality of gas ports 434 while providing sufficient time for most excited radical species to relax into ground-state radical species. In certain embodiments, the dimensions of the plurality of gas ports 434 can be configured such that the residence time of gas passing through the multi-port gas distributor 406 is greater than the typical energy relaxation time of excited radical species. Excited radical species of the hydrogen source gas can be represented by •H ^* in FIG4 , and ground-state radical species of the hydrogen source gas can be represented by • H in FIG4 .

In certain embodiments, excited radical species exiting the plurality of gas ports 434 may flow into a relaxation region 438 contained within the interior of the reaction chamber 404. The relaxation region 438 is located upstream of the chemical vapor deposition region 408 but downstream of the multi-port gas distributor 406. Substantially all, or at least 90%, of the excited radical species exiting the multi-port gas distributor 406 are converted into relaxed radical species in the relaxation region 438. In other words, substantially all excited radical species (excited hydrogen radicals) that enter the relaxation region 438 become de-excited or converted into relaxed radical species (e.g., ground-state hydrogen radicals) before exiting the relaxation region 438. In some embodiments, the process conditions or geometry of the relaxation region 438 can be configured such that the residence time (e.g., determined by the mean free path and the average molecular velocity) of the radical species flowing through the relaxation region 438 causes the relaxed radical species to egress from the relaxation region 438.

As the radical species are delivered from the multi-port gas distributor 406 to the relaxation region 438, one or more silicon-containing precursors and/or one or more co-reactants can be introduced into the chemical vapor deposition region 408. The one or more silicon-containing precursors can be introduced through the gas distributor or gas outlet 442, wherein the gas outlet 442 can be fluidly coupled to the precursor supply 440. The relaxation region 438 can be contained within the space between the multi-port gas distributor 406 and the gas outlet 442. The gas outlet 442 can include openings spaced apart from each other so as to introduce a flow of the one or more silicon-containing precursors in a direction parallel to the gas mixture flowing out of the relaxation region 438. The gas outlet 442 may be located downstream of the multi-port gas distributor 406 and the relaxation zone 438. The gas outlet 442 may be located upstream of the chemical vapor deposition zone 408 and the substrate 412. The chemical vapor deposition zone 408 is located within the reaction chamber 404 and between the gas outlet 442 and the substrate 412.

Substantially all of the flow of one or more silicon-containing precursors can be prevented from mixing with excited radical species adjacent to the multi-port gas distributor 406. Relaxed or ground-state radical species mix with the one or more silicon-containing precursors in a region adjacent to the substrate 412. The chemical vapor deposition region 408 includes a region adjacent to the substrate 412 in which the relaxed or ground-state radical species mix with the one or more silicon-containing precursors. During CVD formation of the silicon carbide film, the relaxed or ground-state radical species mix with the one or more silicon-containing precursors in the gas phase.

In some embodiments, a co-reactant may be introduced from the gas outlet 442 and flowed with one or more silicon-containing precursors. The co-reactant may include a carbon-containing precursor as described below. The co-reactant may be introduced downstream of the remote plasma source 402. The co-reactant may be supplied from the precursor supply source 440 or other source (not shown) fluidly coupled to the gas outlet 442. The co-reactant may be a carbon-containing precursor as described below. In some embodiments, the co-reactant may be introduced from the multi-port gas distributor 406 and flowed into the reaction chamber 404 along with the free radical species generated in the remote plasma source 402. This may include free radicals and/or ions of the co-reactant gas provided in the remote plasma source 402. Co-reactants may be supplied from an additional gas supply 428.

The gas outlet 442 can be separated from the multi-port gas distributor 406 by a sufficient distance to prevent reverse diffusion or reverse flow of one or more silicon-containing precursors. In some embodiments, the gas outlet 442 can be separated from the plurality of gas ports 434 by a distance between about 0.5 inches and about 5 inches, or between about 1.5 inches and about 4.5 inches, or between about 1.5 inches and about 3 inches.

Process gases can be removed from the reaction chamber 404 via an outlet 448 configured to be fluidically coupled to a pump (not shown). Thus, excess silicon-containing precursors, co-reactants, radical species, and dilution and displacement or purge gases can be removed from the reaction chamber 404. In some embodiments, a system controller 450 is in operative communication with the plasma processing apparatus 400. In some embodiments, the system controller 450 includes a processor system 452 (e.g., a microprocessor) configured to execute instructions stored in a data system 454 (e.g., a memory). In some embodiments, the system controller 450 can communicate with the plasma generator controller 422 to control plasma parameters and/or conditions. In some embodiments, the system controller 450 can communicate with the pedestal 414 to control the pedestal height and temperature. In some embodiments, the system controller 450 can control other processing conditions, such as RF power settings, frequency settings, duty cycle, pulse time, pressure within the reaction chamber 404, pressure within the remote plasma source 402, gas flow rates from the source gas supply 426 and the additional gas supply 428, gas flow rates from the precursor supply 440 and other sources, the temperature of the pedestal 414, and the temperature of the reaction chamber 404.

The aspects of controller 450 described below in FIG. 4 also apply to controller 340 in FIG. 3 . Controller 450 may include instructions for controlling process conditions for the operation of plasma processing apparatus 400. Controller 450 typically includes one or more memory devices and one or more processors. The processor may include a CPU or computer, analog and/or digital input/output connections, a stepper motor controller board, etc. Instructions for performing appropriate control operations are executed on the processor. These instructions may be stored on a memory device associated with controller 450 or provided via a network.

In some embodiments, the controller 450 controls all or most of the activities of the plasma processing apparatus 400 described herein. For example, the controller 450 can control all or most of the activities of the plasma processing apparatus 400 associated with depositing a silicon carbide film and, optionally, other operations in a manufacturing process involving the silicon carbide film. The controller 450 can execute system control software that includes multiple sets of instructions for controlling timing, gas composition, gas flow rates, process chamber pressure, chamber temperature, RF power levels, substrate position, and/or other parameters. In some embodiments, other computer programs, scripts, or routines stored on a memory device associated with the controller 450 can be used. In order to provide relatively mild reaction conditions in the environment adjacent to substrate 412, parameters such as RF power level, gas flow rate to plasma region 424, gas flow rate to chemical vapor deposition region 408, and plasma ignition timing may be adjusted and maintained by controller 450. Additionally, adjusting the substrate position may further reduce the presence of high-energy radical species in the environment adjacent to substrate 412. In a multi-station reactor, the controller 450 may contain different or the same instructions for different equipment stations, thereby allowing the equipment stations to operate independently or simultaneously.

In some embodiments, the controller 450 may include instructions for, for example, flowing one or more silicon-containing precursors into the reaction chamber 404 through the gas outlet 442, providing a source gas to the remote plasma source 402, generating one or more radical species of the source gas in the remote plasma source 402, and introducing the one or more radical species in a substantially low energy state from the remote plasma source 402 into the reaction chamber 404 to react with the one or more silicon-containing precursors to deposit a silicon carbide film on the substrate 412. The one or more radical species in the environment of the reaction chamber 404 adjacent to the substrate 412 may be hydrogen radicals in a ground state. In some embodiments, controller 450 may include instructions for flowing a co-reactant along with one or more silicon-containing precursors into reaction chamber 404. The co-reactant may be a hydrocarbon molecule, and each of the one or more silicon-containing precursors may have at least two hydrogen atoms bonded to silicon atoms.

In some embodiments, the apparatus 400 may include a user interface associated with the controller 450. The user interface may include a display screen, a graphical software display of the apparatus 400 and/or process conditions, and a user input device such as a pointing device, a keyboard, a touch screen, a microphone, etc.

The computer program code for controlling the above operations can be written in any known computer-readable programming language, such as assembly language, C, C++, Pascal, Fortran, or other languages. The compiled object code or script can be executed by a processor to perform the tasks specified in the program.

Signals for monitoring the processing may be provided via analog and/or digital input connections of the system controller. Signals for controlling the processing are output on analog and digital output connections of the processing system.

Generally speaking, the methods described herein can be performed on systems comprising semiconductor processing equipment, such as one or more processing tools, one or more chambers, one or more processing stages, and/or specific processing components (wafer pedestals, airflow systems, etc.). These systems can be integrated with electronic devices to control their operation before, during, and after processing of semiconductor wafers or substrates. Generally speaking, these electronic devices are referred to as controllers, which can control various components or subcomponents of one or more systems. Depending on the requirements of the process and/or the type of system, the controller can be programmed to control any of the processes disclosed herein, including the delivery of process gases, temperature settings (e.g., heating and/or cooling), pressure settings, vacuum settings, power settings, RF generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, position and operation settings, wafer transport to and from tools and other transport tools connected to or interfacing with a particular system, and/or load locks.

Broadly speaking, a controller can be defined as an electronic device that includes various integrated circuits, logic, memory, and/or software that receive commands, send commands, control operations, enable clean operations, enable endpoint measurements, and so on. The integrated circuits can include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application-specific integrated circuits (ASICs), and/or one or more microprocessors or microcontrollers that execute program instructions (such as software). Program instructions can be sent to the controller in the form of various individual settings (or program files) that define the operating parameters for performing specific processes on a semiconductor wafer, for a semiconductor wafer, or for a system. In some implementations, the operating parameters may be part of a recipe defined by a process engineer for performing one or more processing steps during the fabrication of one or more layers, materials (e.g., silicon carbide), surfaces, circuits, and/or die on a substrate.

In some embodiments, the controller may be part of or coupled to a computer that is integrated with the system, coupled to the system, connected to the system via a network, or a combination thereof. For example, the controller may be located in the "cloud" or may be all or part of a wafer fab host computer system that allows remote access to substrate processing. The computer may enable remote access to the system to monitor the current progress of manufacturing operations, view the history of past manufacturing operations, view trends or performance indicators from multiple manufacturing operations, change parameters of the current process, configure processing steps to continue the current process, or start a new process. In some examples, a remote computer (e.g., a server) may provide process recipes to the system via a network, which may include a local area network or the Internet. The remote computer may include a user interface that enables the input or programming of parameters and/or settings, which are then transmitted from the remote computer to the system. In some examples, the controller receives instructions in the form of data that specifies parameters for each of the processing steps to be performed during one or more operations. It should be understood that the parameters may be specific to the type of processing to be performed and the type of tool that the controller is configured to interface with or control. Thus, as described above, the controller can be decentralized, for example by including one or more separate controllers that are connected together via a network and work toward a common goal, such as the processing and control described herein. An example of a separate controller used for such purposes would be one or more integrated circuits on the chamber that communicate with one or more integrated circuits located remotely (e.g., at the platform level or as part of a remote computer) that combine to control processing on the chamber.

In addition to the silicon carbide deposition described herein, example systems may include plasma etch chambers or modules, deposition chambers or modules, spin rinse chambers or modules, metal plating chambers or modules, clean chambers or modules, bevel etch chambers or modules, physical vapor deposition (PVD) chambers or modules, chemical vapor deposition (CVD) chambers or modules, atomic layer deposition (ALD) chambers or modules, atomic layer etch (ALE) chambers or modules, ion implantation chambers or modules, path chambers or modules, and any other semiconductor processing system that may be associated with or used in the fabrication and/or production of semiconductor wafers.

As described above, depending on the process step(s) to be performed by the tool, the controller may communicate with one or more of the following in the semiconductor fabrication facility: other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, nearby tools, tools throughout the facility, a host computer, another controller, or tools used in material handling to transport wafer containers to and from tool locations and/or load ports.

The apparatus/processes described herein may be used with, for example, lithographic patterning tools or processes used to manufacture semiconductor devices, displays, LEDs, photovoltaic panels, etc. Typically, although not necessarily, such tools/processes are used or performed together in a common manufacturing facility. Lithographic patterning of thin films typically includes some or all of the following operations, each of which is provided by several possible tools: (1) coating of the photoresist on a workpiece (i.e., substrate) using a spin-on or spray-on tool; (2) curing of the photoresist using a hot plate or oven or UV curing tool; (3) exposing the photoresist to visible light, UV light, or x-ray light using a tool (e.g., a wafer stepper); (4) developing the photoresist so that it can be selectively removed and patterned using a tool (e.g., a wet bench); (5) transferring the photoresist pattern to an underlying film or workpiece using a dry or plasma-assisted etch tool; and (6) removing the photoresist using a tool (e.g., an RF or microwave plasma photoresist stripper). Remote plasma CVD using silicon-containing precursors and carbon-containing precursors

The deposition of silicon carbide films (including silicon carbonitride films) using ALD presents a number of challenges, including thermodynamic challenges that can make ALD of silicon carbide films difficult to achieve. Furthermore, ALD deposition rates are slower than typical CVD techniques, which can be undesirable in manufacturing processes. Furthermore, incorporating carbon into silicon-based or silicon nitride-based films without compromising the step coverage, film density, and/or film quality characteristics of the silicon carbide film can be difficult. The present invention relates to the deposition of silicon carbide films using remote plasma CVD. The present invention allows carbon to be incorporated into a silicon-based film or a silicon nitride-based film without forming any C-C or N-C bonds. The presence of C-C or N-C bonds can adversely affect the properties of the silicon carbide film.

As described above, the deposition reaction for depositing a silicon carbide film may include co-reactants in addition to the silicon-containing precursor and the radical species. The introduction of the co-reactants can be used to tune the composition of the silicon carbide film. The co-reactants can be flowed into the reaction chamber together with the silicon-containing precursor, wherein the co-reactants can flow downstream of the remote plasma source. For example, the gas outlet for introducing the silicon-containing precursor and the co-reactants can be located downstream of the remote plasma source. The remote plasma source is considered to be upstream of the substrate and the environment adjacent to the substrate. In some embodiments, the gas outlet for introducing the silicon-containing precursor and the co-reactants can be located downstream of the remote plasma source and upstream of the substrate and the environment adjacent to the substrate.

In addition to the silicon-containing precursor, a co-reactant may be introduced as a second precursor. The second precursor has chemical properties for tuning the composition of the silicon carbide film. In some embodiments, the second precursor has chemical properties for improving the step coverage of the silicon carbide film. The step coverage of the deposited silicon carbide film can be measured relative to one or more features of the substrate. As used herein, "feature" may refer to a non-planar structure on a substrate, typically a surface that is modified during semiconductor device processing operations. Examples of features include trenches, through-holes, pads, pillars, domes, etc. Features typically have an aspect ratio (depth or height to width). In some embodiments, the step coverage of the silicon carbide film is at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 99%.

In some embodiments, the co-reactant is a hydrocarbon molecule. The co-reactant of the present invention may also be referred to as a carbon-containing precursor, which flows with the silicon-containing precursor. In some embodiments, the hydrocarbon molecule may be a short-chain hydrocarbon molecule having at least one double bond or at least one triple bond. For example, the hydrocarbon molecule comprises a carbon chain between 3 carbon atoms and 7 carbon atoms. The hydrocarbon molecule may contain one or more unsaturated carbon bonds, such as one or more carbon-carbon double bonds or triple bonds. Thus, the hydrocarbon molecule may contain an alkene or alkynyl group. Examples of suitable hydrocarbon molecules include propylene, ethylene, butene, pentene, butadiene, pentadiene (e.g., 1,4-pentadiene), hexadiene, heptadiene, toluene, and benzene. Other examples of suitable hydrocarbon molecules include acetylene, propyne, butyne, pentyne (eg, 1-pentyne), and hexyne (eg, 2-hexyne).

The carbon-containing precursor may flow with one or more silicon-containing precursors. In certain embodiments, each of the silicon-containing precursors does not have C-O bonds and C-N bonds. Each of the silicon-containing precursors may contain two or more Si-H bonds. In practice, each of the silicon-containing precursors has at least one silicon atom and two or more hydrogen atoms bonded thereto. Thus, the at least one silicon atom does not have more than two carbon atoms, nitrogen atoms, and/or oxygen atoms bonded thereto. Examples of silicon-containing precursors include, but are not limited to, silanes and higher silanes, or alkylsilanes and higher alkylsilanes. For example, the silicon-containing precursor can be silane, disilane, trisilane, methylsilane, or dimethylsilane. Therefore, the silicon-containing precursor flowing with the carbon-containing precursor can be a silane-based precursor. The silane-based precursor has one silicon atom with four substituents bonded to the silicon atom. Of the four substituents on the silicon atom, at least two are hydrogen.

A carbon-containing precursor and a silicon-containing precursor are introduced into the reaction chamber downstream of one or more free radical species. The free radical species may be generated in a remote plasma source upstream of a gas outlet for introducing the carbon-containing precursor and the silicon-containing precursor. The free radical species may include hydrogen radicals, wherein upon mixing or interaction with the carbon-containing precursor and the silicon-containing precursor, the hydrogen radicals are in a substantially low energy state or ground state.

When depositing silicon carbide films by remote plasma CVD, most, if not all, of the Si-C bonds in the film are typically provided by existing Si-C bonds in the silicon-containing precursor. This can limit the ability to tune the composition of the silicon carbide film. Flowing a co-reactant with the silicon-containing precursor allows for greater flexibility in tuning the composition of the film, allowing for more or less carbon to be incorporated into the film. However, when the co-reactant is a carbon-containing precursor, the co-reactant does not contribute to the compositional tuning of the silicon carbide film, or the co-reactant may add C-C, C-O, or C-N bonds that may adversely affect the electrical properties and/or step coverage of the silicon carbide film. In the present invention, the carbon-containing co-reactant and the silicon-containing precursor are selected so that the carbon-containing co-reactant contributes to the compositional tuning of the silicon carbide film without adding C-C, C-O, or C-N bonds. Compared to silicon carbide films deposited using existing Si-C bonding in silicon-containing precursors, the carbon-containing co-reactant and silicon-containing precursor add additional process parameters for tuning the composition of the silicon carbide film while maintaining or improving film quality.

Hydrogen radicals in a substantially low energy state or ground state can interact with carbon-containing precursors and silane-based precursors. Without being bound by theory, one of the more kinetically favorable reaction mechanisms in the deposition reaction involves hydrogen abstraction, which involves the selective cleavage of Si-H bonds in the silane-based precursor. The hydrogen abstraction reaction results in an activated silane-based precursor. Without being bound by theory, hydrogen radicals in a substantially low energy state or ground state can interact with alkyne or alkene groups in hydrocarbon molecules, resulting in the formation of activated alkanes (e.g., methane). In some cases, the hydrocarbon molecules break into short-chain hydrocarbon molecules or radicals. Activated alkanes contain carbon radicals as activation sites, and activated silane-based precursors contain silicon radicals as activation sites, and these activation sites can react together to form Si-C bonds. Figure 5 shows the chemical reaction between the activated alkane from the carbon-containing precursor and the activated silane-based precursor.

Rather than being passive bystanders, carbon-containing precursors can significantly contribute to the composition of silicon carbide films. The carbon-containing precursor, and any byproducts of reactions with hydrogen radicals in a substantially low energy state or ground state, can be incorporated into the silicon carbide film in substantial amounts. As used herein, the term "substantial" with respect to incorporation of carbon from the carbon-containing precursor into the silicon carbide film can refer to a change in carbon atomic concentration equal to or greater than about 5% compared to a silicon carbide film deposited without the carbon-containing precursor. The contribution of carbon from the carbon-containing precursor prevents or minimizes the introduction of C-C bonds. The silicon carbide film has no or substantially no C-C bonds. In some embodiments, the percentage of C-C bonds in the silicon carbide film is equal to or less than about 2%, equal to or less than about 1%, equal to or less than about 0.5%, or even 0%.

The remote plasma CVD process of the present invention may include a remote hydrogen plasma, wherein hydrogen radicals interact with a carbon-containing precursor and a silicon-containing precursor downstream of the remote plasma source. In certain embodiments, the remote hydrogen plasma may further include a remote nitrogen plasma or a remote oxygen plasma. A nitriding agent or an oxidizing agent may be added to the remote plasma source to generate nitrogen radicals or oxygen radicals, respectively. The nitriding agent may promote the formation of a silicon carbonitride (SiCN) film, while the oxidizing agent may promote the formation of a silicon oxycarbide (SiCO) film.

When forming a SiCN film, a nitriding agent and hydrogen may be provided to a remote plasma source. In some embodiments, a carrier gas (e.g., helium) is provided to the remote plasma source to mix with the nitriding agent and hydrogen. Free radicals of the nitriding agent and hydrogen may be generated in the remote plasma source. In some embodiments, the nitriding agent comprises nitrogen ( _N2 ) or ammonia ( _NH3 ). The free radicals of the nitriding agent may be introduced from the remote plasma source into the reaction chamber along a flow path of the hydrogen free radicals. The free radicals of the nitriding agent and hydrogen react with one or more silicon-containing precursors and co-reactants to form the SiCN film. Without being bound by theory, amine radicals or nitrogen radicals interact with the activated silicon-containing precursor to form Si-N bonds. The SiCN film has no or substantially no CC bonds and no or substantially no CN bonds. In certain embodiments, the percentage of CC bonds or CN bonds in the SiCN film is about 2% or less, about 1% or less, about 0.5% or less, or even 0%.

When forming a SiCO film, an oxidant and hydrogen may be provided to a remote plasma source. In certain embodiments, a carrier gas (e.g., helium) is provided to the remote plasma source to mix with the oxidant and hydrogen. Free radicals of the oxidant and hydrogen may be generated in the remote plasma source. In certain embodiments, the oxidant comprises carbon dioxide ( _CO2 ), carbon monoxide (CO), oxygen ( _O2 ), ozone ( _O3 ), or nitrous oxide ( _N2O ). The free radicals of the oxidant may be introduced from the remote plasma source into the reaction chamber along a flow path of the free radicals of hydrogen. The free radicals of the oxidant and hydrogen react with one or more silicon-containing precursors and co-reactants to form the SiCO film. Without being bound by theory, oxygen radicals interact with the activated silicon-containing precursor to form Si-O bonds. The SiCO film has no or substantially no CC bonds and no or substantially no CO bonds. In certain embodiments, the percentage of CC bonds or CO bonds in the SiCO film is about 2% or less, about 1% or less, about 0.5% or less, or even 0%.

Figure 6A shows an FTIR spectrum of remote plasma CVD of silicon carbide films using a silicon-containing precursor and varying amounts of a carbon-containing precursor. Figure 6B shows a magnified portion of the FTIR spectrum in Figure 6A. The carbon-containing precursor and the silicon-containing precursor were provided downstream of the remote plasma. The remote plasma contained hydrogen and nitrogen radicals. 6A–6B show several plots of FTIR spectra. The plot with the highest peak is for a carbon-containing precursor with a flow rate of 0 sccm, the plot with the second highest peak is for a carbon-containing precursor with a flow rate of 1 sccm, the plot with the third highest peak is for a carbon-containing precursor with a flow rate of 3 sccm, the plot with the fourth highest peak is for a carbon-containing precursor with a flow rate of 5 sccm, the plot with the fifth highest peak is for a carbon-containing precursor with a flow rate of 10 sccm, the plot with the sixth highest peak is for a carbon-containing precursor with a flow rate of 15 sccm, and the plot with the shortest peak is for a carbon-containing precursor with a flow rate of 24 sccm. Si-N bonds can be observed at approximately 835 cm ^-1 , and Si-C bonds can be observed at approximately 790 cm ^-1 .

In the absence of a carbon-containing precursor, a silicon nitride film is deposited when a silicon-containing precursor reacts with a remote plasma containing nitrogen radicals. Introducing a carbon-containing precursor results in the formation of a silicon carbonitride film. Silicon carbonitride films contain both Si-N and Si-C bonds. As shown in Figures 6A–6B, increasing the flow rate of the carbon-containing precursor increases the amount of Si-C bonds in the silicon carbonitride film. The Si-C bonds are a result of the carbon-containing precursor. Although Si-C bonds typically exist from a single silicon-containing precursor, the present invention can introduce a silicon-containing precursor and a carbon-containing precursor to form Si-C bonds in doped or undoped silicon carbide films.

Figure 7 shows a TEM image of a silicon carbide film deposited on a substrate feature using a silicon-containing precursor and a carbon-containing precursor. The remote plasma contains hydrogen and nitrogen radicals. X-ray photoelectron spectroscopy (XPS) data can identify the composition of the deposited film, including the silicon carbide film in Figure 7. Table 1 shows a summary of the XPS data compiled for the silicon carbide film. The elemental composition is expressed as atomic percent concentration and shows the atomic percent ratios of carbon to silicon (C/Si), nitrogen to silicon (N/Si), and carbon to nitrogen (C/N). As shown in Table 1, the introduction of a carbon-containing precursor produces a doped silicon carbide film with a high carbon content. [Table 1] Si (at.%) O (at.%) C (at.%) F (at.%) N (at.%) C/Si N/Si C/N SiCN 31.7 7.5 51.4 0.6 8.9 1.62 0.28 5.78

The introduction of a second precursor, particularly a carbon-containing precursor, significantly improves the step coverage of the silicon carbide film. In certain embodiments, the step coverage of the silicon carbide film is at least 75%, at least 80%, at least 85%, or at least 90%. Even with the introduction of a carbon-containing precursor, film quality and film density are substantially maintained. For example, the film density can be equal to or greater than about 2.0 g/cm ³ . Structure and Properties of the Deposited Film

The deposited film comprises silicon, carbon, and in some cases, oxygen, nitrogen, and/or one or more other elements. In certain embodiments, the atomic concentration of silicon is between approximately 15% and 45% (or approximately 25% to 40%), the atomic concentration of carbon is between approximately 10% and 50%, the atomic concentration of oxygen is between approximately 0% and 45%, and the atomic concentration of nitrogen is between approximately 0% and 45%. In one example, the atomic concentration of silicon is approximately 30%, the atomic concentration of oxygen is approximately 25%, and the atomic concentration of carbon is approximately 45%. In another example, the atomic concentration of silicon is approximately 30%, the atomic concentration of oxygen is approximately 45%, and the atomic concentration of carbon is approximately 25%. In another example, the film contains about 10-15% carbon and about 30-40% oxygen, both based on atomic concentrations. In all cases, the film contains some hydrogen. However, it should be understood that the relative atomic concentration of hydrogen is small, for example, equal to or less than about 5%. It should be understood that the relative atomic concentration can vary depending on the choice of precursor. Silicon atoms form bonds with carbon and, optionally, with nitrogen and/or oxygen atoms. In some embodiments, the deposited film contains more Si-C bonds than Si-N bonds. In some examples, the deposited film contains a ratio of Si-C bonds to Si-N bonds between about 0.5:1 and 3:1. In some embodiments, the film density is between about 2 and 2.7 g/ ^cm3 .

When using a carbon-containing precursor and a silicon-containing precursor having at least two hydrogen atoms bonded to silicon atoms, the relative atomic concentrations of silicon and carbon can be relatively high compared to other elements in the silicon carbide film. In certain embodiments, the relative atomic concentration of silicon can be at least 25% or at least 30%, and the relative atomic concentration of carbon can be at least 25%, at least 30%, or at least 40%. Furthermore, for the doped silicon carbide film, the relative atomic concentration of oxygen can be less than approximately 10%, and the relative atomic concentration of nitrogen can be less than approximately 10%.

In certain embodiments, the internal structure of the precursor is retained in the deposited film. This structure may retain all or most of the Si-C, and Si-O and/or Si-N bonds (if present) in the precursor, while linking or cross-linking the functional moieties of the respective precursors via bonds at Si-H and/or Si-Si bonding sites present in the precursor molecules and/or via additional condensation reactions on the growth surface if sufficient heat is provided.

The process conditions previously described herein can provide highly conformal thin film structures. The relatively mild process conditions can minimize ion bombardment at the substrate surface, resulting in a non-directional deposition. Furthermore, the relatively mild process conditions can reduce the number of free radicals with high viscosity coefficients, which tend to adhere to the sidewalls of previously deposited layers or films. In certain embodiments, for aspect ratios of approximately 2:1 to 10:1, silicon carbide films can be deposited with a conformality of between about 25% and 100%, more typically between about 50% and 100%, and even more typically between about 80% and 100%. Conformality can be calculated by comparing the average thickness of the deposited film on the bottom, sidewalls, or top of the feature to the average thickness of the deposited film on the bottom, sidewalls, or top of the upper feature. For example, conformality can be calculated by dividing the average thickness of the deposited film on the sidewalls by the average thickness of the deposited film at the top of the feature and multiplying by 100 to obtain a percentage. For some applications, a conformality of between about 85% and 95% is sufficient. In some examples, the conformality of silicon carbide deposited on features with aspect ratios between about 2:1 and about 4:1 is at least about 90%. Some BEOL processes (back end of line processes) fall into this category. In some examples, silicon carbide is deposited on features with aspect ratios between about 4:1 and about 6:1 with a conformality of at least about 80%. Certain spacer deposition processes fall within this category. In some examples, silicon carbide is deposited on features with aspect ratios between about 7:1 and about 10:1 (and even higher) with a conformality of at least about 90%. Certain DRAM (dynamic random access memory) manufacturing processes fall within this category.

The process conditions can also provide a thin film structure with high breakdown voltage and low leakage current. By introducing a limited amount of oxygen or nitrogen into SiC-type materials, the leakage path provided by Si-H bonds and/or Si- _CH2 -Si bonds can be blocked by oxygen or nitrogen. The conduction mode in Si-O and Si-N may be different at low electric fields. This can provide improved electrical properties while maintaining a relatively low dielectric constant. In various embodiments, the film has an effective dielectric constant of about 5 or less, or about 4.0 or less, in some cases about 3.5 or less, in some cases about 3.0 or less, and even in some embodiments about 2.5 or less. The effective dielectric constant can depend on bonding and density. In some embodiments, SiOC films are made to have a dielectric constant of 6 or higher, especially when the carbon content is relatively high. If leakage current is a significant concern, SiOC films require a dielectric constant less than 5. The lower the dielectric constant, the poorer the sealing, barrier, and thermal resistance properties. In certain embodiments where applications require low sealing and diffusion confinement, excellent etch resistance, and thermal stability, the silicon carbide film can be made dense and highly cross-linked. This can be achieved, for example, by a) depositing the film at relatively high temperatures and/or b) providing a relatively high radical:precursor ratio. In some embodiments, the silicon carbide film can be relatively thin and still serve as an effective seal and diffusion barrier.

In certain embodiments, the deposited film may be porous. As previously discussed herein, silicon-containing precursors may include cyclic siloxanes and cage siloxanes. These precursors, and others with significant internal open space, can introduce significant porosity into the structure of the deposited film. The porosity in the deposited film can further reduce the dielectric constant. In certain embodiments, the deposited silicon carbide film has a porosity of between about 20% and 50%. The pore size of the porous film can follow the pore size of the ring or cage shaped precursor. In certain embodiments, the average pore size of the film is between about 5Å and 20Å, for example, about 16Å. Applications

The present invention can be further understood by referring to the applications of high-quality silicon carbide films described below, which are purely illustrative. The present invention is not limited to the scope of specific applications, which are merely examples of aspects of the present invention.

In some embodiments, a silicon carbide film can be deposited over exposed copper. In some embodiments of depositing the silicon carbide film, the reaction conditions near the substrate may be free of oxidizing agents (e.g., O ₂ , O ₃ , and CO ₂ (including their free radicals)). Therefore, the silicon carbide film can be deposited directly over the exposed copper without oxidizing the copper (e.g., forming copper oxide). Such a film can serve as an etch stop layer and can also act as a copper diffusion barrier. The presence of the silicon carbide film can provide a sufficiently low dielectric constant and excellent leakage characteristics to serve as a diffusion barrier. The silicon carbide film itself can serve as an etch stop and/or diffusion barrier, or as a bilayer stack (e.g., a SiCO/SiNC bilayer deposited over exposed copper). In some embodiments, the silicon carbide film can be placed between adjacent metallization layers, typically produced by a damascene process. The silicon carbide film is resistant to etching and can be sufficiently dense to minimize diffusion of copper ions into adjacent areas of the dielectric material. In some embodiments, nitrogen can be incorporated into the film by using nitrogen-containing precursors or plasma to activate nitrogen-containing radicals (e.g., elemental nitrogen radicals or amine radicals).

In certain embodiments, as shown in FIG. 1B , a silicon carbide film 111 may be conformally deposited on features 112 of substrate 110 . Features 112 may be isolated or densely packed, wherein features 112 may have a relatively small critical dimension (CD). In certain embodiments, the features may have a CD of approximately 20 nm or less, approximately 10 nm or less, or approximately 5 nm or less. The aspect ratio of the height to the width of features 112 may be greater than 2:1, greater than 5:1, greater than 10:1, or greater than 20:1. The step coverage of silicon carbide film 111 deposited on features 112 may be at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 99%.

In some embodiments, a silicon carbide film can be deposited as a vertical structure adjacent to a metal or semiconductor structure. The silicon carbide deposition provides excellent step coverage along the sidewalls of the metal or semiconductor structure, resulting in a vertical structure. In some embodiments, the vertical structures can be referred to as spacers or pads.

FIG1C shows a cross-section of a silicon carbide liner deposited on the sidewalls of a transistor's gate electrode structure. As shown in FIG1C , the transistor may be a CMOS transistor, wherein a silicon substrate 120 has a source 122 and a drain 123. A gate dielectric 124 may be deposited over the silicon substrate 120, and a gate electrode 125 may be deposited over the gate dielectric 124 to form the transistor. Silicon carbide spacers or liner 121 may be deposited on the sidewalls of the gate electrode 125 and on the gate dielectric 124.

In another example, FIG1D shows a cross-section of silicon carbide deposited on the sidewalls of an exposed copper line in an air-gapped metallization layer. Air gaps 130 can be introduced into an integrated circuit layer between copper lines 132, which can reduce the effective dielectric constant of the film layer. Silicon carbide pads 131 can be deposited on the sidewalls of copper lines 132, and a non-conformal dielectric layer 133 can be deposited over air gaps 130, pads 131, and copper lines 132. Examples of such air-gapped metallization layers are described in U.S. Patent Publication No. 2004/0232552 to Fei Wang et al., which is incorporated herein by reference in its entirety for all purposes.

In some embodiments, a silicon carbide film can be deposited on the sidewalls of a patterned porous dielectric material. Ultra-low-k dielectric materials can be fabricated with porous structures. The pores in such materials provide areas for metal to enter during the deposition of subsequent film layers, including the deposition of diffusion barriers containing metals such as tantalum (Ta). If too much metal migrates into the dielectric material, it can cause shorts between adjacent copper metallization lines.

FIG1E shows a cross-section of a silicon carbide film used as a pore filler in a porous dielectric material. Porous dielectric layer 142 may have trenches or through-holes cut into porous dielectric layer 142 to form pores 140. Silicon carbide film 141 may be deposited along pores 140 to effectively seal them. Sealing pores 140 with silicon carbide film 141 avoids damage to porous dielectric layer 142, which may occur with other sealing techniques using plasma. Silicon carbide film 141 can be sufficiently dense to function as a pore filler. In some embodiments, the etched dielectric material (e.g., porous dielectric layer 142) may first be subjected to a "k-recovery" process that exposes the porous dielectric layer 142 to UV radiation and a reducing agent. This recovery process is further described in co-owned U.S. Patent Publication No. 2011/0111533 to Varadarajan et al., which is incorporated herein by reference in its entirety for all purposes. In another "k-recovery" process, the porous dielectric layer 142 may be exposed to UV radiation and a chemical silanizing agent. This recovery process is further described in co-owned U.S. Patent Publication No. 2011/0117678 to Varadarajan et al., which is incorporated herein by reference in its entirety for all purposes. After exposing the pores 140 to a recovery treatment to render the surface more hydrophilic and provide a monolayer of material, a conformally deposited silicon carbide film 141 may be deposited to effectively seal the pores 140 of the porous dielectric layer 142.

In some embodiments, a silicon carbide film can be deposited to serve as an ultra-low-k dielectric material itself. An ultra-low-k dielectric material is conventionally defined as a material having a dielectric constant less than 2.5. In such configurations, the ultra-low-k dielectric material of silicon carbide can be a porous dielectric layer. Porosity in the dielectric layer can be introduced by using ring-shaped or cage-shaped precursor molecules, including cyclosiloxanes and silsesquioxanes. In one example, the porosity of the ultra-low-k dielectric layer of silicon carbide can be between about 20% and 50%. Furthermore, the ultra-low-k dielectric layer can have an average pore size of less than about 100 Å, for example, between about 5 Å and 20 Å. For example, a cyclosiloxane ring can have a radius of approximately 6.7 Å. Although increasing the number and size of pores can lower the dielectric constant, making the dielectric layer too porous may compromise its mechanical integrity.

In the above description, numerous specific details are set forth to provide a thorough understanding of the presented embodiments. The disclosed embodiments may be practiced without some or all of these specific details. In other instances, well-known process operations are not described in detail in order to avoid obscuring the present invention. Although the disclosed embodiments are described in conjunction with specific embodiments, it should be understood that this is not intended to limit the disclosed embodiments.

The above embodiments have been described in detail to enable those skilled in the art to clearly understand the present invention. It should be understood that certain changes and modifications may be made within the scope of the appended claims. It should be noted that there are many alternative ways of implementing the processes, systems, and apparatus of the embodiments herein. Therefore, the embodiments herein are to be considered in all respects illustrative and not restrictive, and the embodiments are not to be limited to the details provided herein.

100: Substrate 101: Silicon carbide film 110: Substrate 111: Silicon carbide film 112: Feature 120: Silicon substrate 121: Silicon carbide spacer/liner 122: Source 123: Drain 124: Gate dielectric 125: Gate electrode 130: Air gap 131: Liner 132: Copper wire 133: Non-conformal dielectric layer 140: Porosity 141: Silicon carbide film 142: Porous dielectric layer 300: Device 310: Reaction chamber 320: Showerhead 330: Substrate 335: Base 340: Controller 350: Container 355: First gas inlet 360: Remote plasma source 365: Second gas inlet 400: Apparatus 402: Remote plasma source 404: Reaction chamber 406: Multi-port gas distributor 408: Chemical vapor deposition area 412: Substrate 414: Base 418: Coil 422: Plasma generator controller 424: Plasma area 426: Source gas supply 428: Gas supply 434: Multiple gas ports 438: Relaxation area 440: Precursor supply 442: Gas outlet 448: Outlet 450: Controller 452: Processor System 454: Data System

FIG. 1A shows a schematic cross-sectional view of an exemplary doped or undoped silicon carbide film deposited on a substrate.

FIG. 1B shows a schematic cross-sectional view of an exemplary doped or undoped silicon carbide film conformally deposited on a feature of a substrate.

FIG1C is a schematic cross-sectional view of an exemplary doped or undoped silicon carbide vertical structure on the sidewall of the transistor gate electrode.

FIG1D shows a schematic cross-sectional view of an exemplary vertical structure of doped or undoped silicon carbide on the exposed sidewall of a copper line in an air-gap metallization layer.

FIG. 1E shows a schematic cross-sectional view of an exemplary doped or undoped silicon carbide pore filler in a porous dielectric material.

Figure 2 shows the chemical structures of representative examples of cage-type siloxane promotors.

FIG3 shows a schematic diagram of an exemplary plasma processing apparatus having a remote plasma source, according to some embodiments.

According to some other embodiments, FIG. 4 shows a schematic diagram of an exemplary plasma processing apparatus having a remote plasma source.

FIG5 shows an example of the chemical reaction between activated alkanes (plural) from carbon-containing precursors and activated silane-based precursors.

FIG6A shows FTIR spectra of remote plasma CVD silicon carbide films using a silicon-containing precursor and varying amounts of carbon-containing precursors.

FIG6B shows an enlarged view of a portion of the FTIR spectrum in FIG6A.

FIG7 shows a TEM image of a silicon carbide film deposited on substrate features using a silicon-containing precursor and a carbon-containing precursor.

400: Equipment

402: Remote Plasma Source

404: Reaction Chamber

406: Multi-port gas distributor

408: Chemical Vapor Deposition Area

412:Substrate

414: Base

418: Coil

422: Plasma Generator Controller

424: Plasma Area

426: Source gas supply unit

428: Gas Supply Department

434: Multiple gas ports

438: Relaxation Area

440: Precursor Supply Source

442: Gas outlet

448: Exit

450: Controller

452: Processor System

454:Data System

Claims (18)

A method for depositing a silicon carbide film on a substrate, the method comprising: Flowing a silicon-containing precursor into a reaction chamber and toward a substrate, wherein the silicon-containing precursor comprises at least one Si-H bond and/or Si-Si bond; Flowing a carbon-containing precursor into the reaction chamber together with the silicon-containing precursor, wherein the silicon-containing precursor and the carbon-containing precursor flow into the reaction chamber through one or more gas outlets downstream of a gas distributor for delivering radical species, wherein the carbon-containing precursor is a hydrocarbon molecule having one or more carbon-carbon double or triple bonds; Generating radical species from a source gas in a remote plasma source, the radical species being generated upstream of the silicon-containing precursor and the carbon-containing precursor, wherein the source gas comprises hydrogen, nitrogen, an N-H-containing species, or a mixture thereof; and introducing the radical species into the reaction chamber and toward the substrate through the gas distributor, wherein the radical species react with the silicon-containing precursor and the carbon-containing precursor to form a doped or undoped silicon carbide film on the substrate. The method of depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the silicon-containing precursor has at least two hydrogen atoms bonded to silicon atoms. The method of depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the hydrocarbon molecule comprises propylene, butene, pentene, butadiene, pentadiene, hexadiene, heptadiene, toluene, benzene, propyne, butyne, pentyne, or hexyne. The method of depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the silicon-containing precursor is silane, disilane, trisilane, methylsilane, or dimethylsilane. A method of depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the silicon carbide film, doped or undoped, has a conformality of between 80% and 100% in one or more recessed features of the substrate. A method for depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the step of introducing the free radical species into the reaction chamber includes continuously introducing the free radical species into the reaction chamber, wherein the free radical species react with the silicon-containing precursor and the carbon-containing precursor in a chemical vapor deposition (CVD) reaction to form the doped or undoped silicon carbide film. The method of depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the radical species include hydrogen radicals. A method for depositing a silicon carbide film on a substrate as claimed in claim 7, wherein the step of introducing the radical species into the reaction chamber includes converting the hydrogen radical from an excited state to a ground state to react with the silicon-containing precursor and the carbon-containing precursor. A method of depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the percentage of C-C bonds in the doped or undoped silicon carbide film is equal to or less than 1% of the bonds in the doped or undoped silicon carbide film. The method of claim 1 for depositing a silicon carbide film on a substrate further comprises: providing a nitriding agent together with the source gas in the remote plasma source, wherein radicals of the nitriding agent are generated in the remote plasma source; and introducing the radicals and radical species of the nitriding agent into the reaction chamber and toward the substrate, wherein the radicals and radical species of the nitriding agent react with the silicon-containing precursor and the carbon-containing precursor to form a silicon carbonitride (SiCN) film. The method of depositing a silicon carbide film on a substrate as claimed in claim 10, wherein the nitriding agent comprises nitrogen ( _N2 ) or ammonia ( _NH3 ). The method of depositing a silicon carbide film on a substrate as claimed in claim 1 further comprises: providing an oxidant with the source gas in the remote plasma source, wherein free radicals of the oxidant are generated in the remote plasma source; and introducing the free radicals and the free radical species of the oxidant into the reaction chamber and toward the substrate, wherein the free radicals and the free radical species of the oxidant react with the silicon-containing precursor and the carbon-containing precursor to form a silicon oxycarbide (SiCO) film. The method of depositing a silicon carbide film on a substrate as claimed in claim 12, wherein the oxidizing agent comprises carbon dioxide ( _CO2 ), carbon monoxide (CO), oxygen ( _O2 ), ozone ( _O3 ), or nitrous oxide ( _N2O ). The method of depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the silicon-containing precursor is a silane-based precursor. A method for depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the silicon carbide film is undoped silicon carbide (SiC). A method of depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the atomic concentration of silicon in the doped or undoped silicon carbide film is at least 25%, and wherein the atomic concentration of carbon in the doped or undoped silicon carbide film is at least 25%. A method of depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the substrate comprises one or more recessed features and each of the one or more recessed features has an aspect ratio of at least 10:1. A method for depositing a silicon carbide film on a substrate as claimed in claim 1, wherein the silicon-containing precursor does not have (i) C-O bonds and (ii) C-N bonds.