CN102881562A - Surface passivation method of germanium-based substrate - Google Patents

Abstract

The invention discloses a surface passivation method of a germanium base substrate, which belongs to the surface passivation method of semiconductor devices. The method includes: 1) cleaning the surface of the semiconductor germanium substrate to remove surface contamination and natural oxide layer; 2) putting the germanium substrate into the plasma chamber; 3) generating plasma by using the reaction gas corresponding to the multi-bond atoms And conduct plasma bath treatment on the germanium sheet; 4) Deposit the gate dielectric, and perform subsequent processes to prepare MOS capacitors or devices. The invention utilizes the method of plasma bath to combine the multi-bond atoms and the germanium surface atoms with dangling bonds without forming the germanium-containing interfacial layer. In this way, the dangling bonds on the surface are passivated to reduce the interface state, and the multi-bond connection between the multi-bond atoms and the germanium atoms adjacent to the germanium surface is used to reduce the probability of the germanium surface atoms detaching from the germanium substrate surface and diffusing, so as to strengthen the germanium surface. atoms and effectively suppress the outdiffusion effect of germanium atoms on the surface; at the same time, it will not introduce an interface layer that is not conducive to the thinning of EOT.

Description

A kind of surface passivation method of germanium base substrate

technical field

The invention belongs to the field of semiconductor devices, and in particular relates to a semiconductor surface passivation method.

Background technique

In the past 40 years, integrated circuit technology has developed rapidly following Moore's law, and the integration and function of integrated circuits have been rapidly improved by reducing the geometric size of metal-oxide-semiconductor field effect transistors (MOSFETs). However, as the feature size of the device is reduced to the nanoscale, the further reduction of the feature size of the device makes the transistor gradually reach the dual limits of physics and technology, and the performance of traditional bulk Si devices is difficult to further improve at the previous speed. One of the effective ways to further improve device performance is to introduce high-mobility channel materials. Due to the high mobility of electrons and holes at the same time (at room temperature (300K), the electron mobility of the germanium channel is 2.4 times that of silicon, and the hole is 4 times that of silicon), germanium materials and germanium-based devices have become a kind of choose.

At present, in the preparation technology of germanium-based MOS devices, the interface problem between the germanium substrate and the gate dielectric is one of the key factors affecting the performance improvement of germanium-based MOS devices. There are two main problems in the interface location, one is the high interface state density, and the other is that the germanium atoms on the surface are easy to diffuse. At present, the main methods to solve this problem can be roughly divided into two categories. One is to use H passivation and Cl passivation in traditional silicon technology to passivate the surface dangling bonds to reduce the interface state, but studies have shown that the passivation effect of this method, such as the formation of Ge-H, Ge-Cl bond chemistry Poor stability, easy to break, cannot effectively suppress the outdiffusion of germanium surface atoms. The second is to insert an ultra-thin layer at the interface between the germanium substrate and the gate dielectric, which can be a dielectric or a semiconductor epitaxial layer, such as SiO2, GeOxNy, Si, etc., but this method is not conducive to the equivalent gate oxide layer thickness ( EOT) thinning.

Therefore, for the preparation of germanium-based devices, a passivation method is needed to simultaneously achieve the following effects: passivation of surface dangling bonds, inhibition of diffusion of germanium atoms on the surface, and facilitation of EOT thinning.

Contents of the invention

In order to meet the needs of the preparation of germanium-based devices, the present invention proposes a process through plasma bath treatment (so-called plasma bath treatment: placing the substrate to be treated in a plasma environment formed by ionization of reactive gas), using multi-bond atoms ( That is, the number of electrons in the outermost shell of the atom is less than 7, and non-metallic atoms that can form multiple covalent bonds, such as nitrogen, sulfur, phosphorus, etc.) realize the surface passivation method of the germanium substrate.

Concrete technical scheme of the present invention is as follows: a kind of surface passivation method of germanium base substrate, its step comprises:

1) Clean the surface of the germanium substrate to remove surface contamination and natural oxide layer;

2) Put the germanium substrate into the plasma chamber;

3) Use the reactive gas corresponding to the multi-bond atoms to generate plasma and perform plasma bath treatment on the germanium substrate;

4) Deposit the gate dielectric, and perform subsequent processes to prepare MOS capacitors or devices.

In the step 1), the semiconductor germanium substrate can be a bulk Ge substrate, a GOI substrate or any substrate with a Ge epitaxial layer on its surface.

The plasma chamber in step 2) may be an inductively coupled plasma chamber, or any other chamber capable of generating plasma.

The reaction gas in step 3) can be an elemental gas corresponding to a multi-bond atom (such as nitrogen corresponding to a nitrogen atom capable of forming three covalent bonds) or a hydride containing a multi-bond atom (such as a hydride that can form three covalent bonds) Ammonia with a nitrogen atom that can form two covalent bonds, hydrogen sulfide that contains a sulfur atom that can form two covalent bonds, and phosphine that contains a phosphorus atom that can form three covalent bonds, etc.), can also be multi-bond atoms Mixed gas of elemental gas (or hydride containing multi-bond atoms) and inert atomic gas (such as Ar gas);

If the reaction gas in the step 3) only uses the elemental gas corresponding to the multibond atom (or the hydride containing the multibond atom), the gas flow rate is 5~100 sccm; for the elemental gas corresponding to the multibond atom (or the hydride containing the multibond atom hydride) and inert atomic gas (such as Ar gas), the flow rates of elemental gas corresponding to multi-bond atoms (or hydride containing multi-bond atoms) and inert atomic gas are 5~100 sccm, 2~ 100 sccm;

The pressure of the reaction gas in the step 3) is 8~200mTorr;

The power used to generate plasma in step 3) is 20-1500W;

The plasma bath treatment time in the step 3) is 5s~60min;

In the steps 1) to 5), the germanium substrate is taken as an example for technical introduction. The germanium substrate substrate can also be a compound semiconductor substrate containing germanium, such as SiGe, GeSn, etc.;

The invention utilizes the method of plasma bath to make active multi-bond atoms form covalent bond connection with germanium surface atoms without forming interface layer of germanium-containing compound. In this way, the surface dangling bonds are passivated to reduce the interface state, and the multi-bond atoms are connected with multiple single-bond bonds of germanium atoms adjacent to the germanium surface to reduce the probability of germanium surface atoms diffusing away from the germanium substrate surface, achieving Strengthen the surface atoms of germanium and effectively suppress the outdiffusion effect of germanium atoms on the surface; at the same time, it will not introduce an interface layer that is not conducive to the thinning of EOT, as shown in Figure 1 (taking nitrogen atom passivation as an example). This method uses ions with a high valence state (<-1 valence) to passivate the surface of germanium, which can effectively passivate the dangling bonds on the surface of germanium, reduce the interface state, and can effectively strengthen the surface atoms of germanium to suppress the diffusion of germanium atoms on the surface. At the same time, it is beneficial to reduce the proportion of EOT.

Description of drawings

Fig. 1 shows the schematic diagram of the principle of the surface passivation method proposed by the present invention;

Fig. 2 shows the flow chart of the surface passivation method proposed by the present invention;

Embodiment surface passivation method schematic diagram shown in Fig. 3;

In the picture:

1—nitrogen atom; 2—germanium atom; 3—semiconductor germanium substrate; 4—gate dielectric.

Detailed ways

The method of the present invention will be further described through specific embodiments below in conjunction with the accompanying drawings and the germanium substrate.

Step 1. The germanium substrate is cleaned, and the surface oxide layer is removed, as shown in Figure 3(a);

Step 2. Putting the cleaned germanium substrate into an inductively coupled plasma chamber, using reactive gas to generate plasma and performing plasma bath treatment on the germanium sheet. The reaction gas can be an elemental gas corresponding to a multi-bond atom or a hydride containing a multi-bond atom, or a mixture of an elemental gas (or a hydride containing a multi-bond atom) corresponding to a multi-bond atom and an inert atomic gas (such as Ar gas). mixed composition. A preferred example of this embodiment is to use a mixed gas of N ₂ and Ar to generate nitrogen plasma, and perform plasma bath treatment on the germanium substrate, as shown in FIG. 3( b ). Wherein, the _N flow rate is 5-100 sccm, and the preferred embodiment of the present embodiment is 16 sccm; the Ar flow rate is 2-100 sccm, and the preferred embodiment of the present embodiment is 4 sccm; The power of bulk treatment is 20~1500W, and the preferred embodiment of this embodiment is 500W; the substrate temperature is room temperature; the time of plasma bath treatment is 5s~60min, such as 2min.

Step 3. Depositing a gate dielectric on the germanium substrate, as shown in FIG. 3(c). Among them, the gate dielectric can be SiO ₂ , Al ₂ O ₃ , Y ₂ O ₃ , HfO ₂ , ZrO ₂ , GeO ₂ , La ₂ O _{3 ,} etc., and methods such as sputtering, CVD, ALD, MBE, etc. can be used; the thickness of the gate dielectric is between 2~20nm, such as 5nm;

The above embodiments describe the surface passivation method proposed by the present invention in detail. The multi-bond atoms can be nitrogen or other polyvalent element atoms, and the reaction gas can be a multi-bond atom gas (such as a multi-bond atom gas (such as a multi-bond Atomic nitrogen corresponds to nitrogen gas).

Those skilled in the art should understand that the above description is only a specific embodiment of the present invention, and within the scope not departing from the essence of the present invention, other materials can be used to achieve the passivation effect of the present invention, and the same method can also be used in the embodiment The same effect is obtained on other semiconductor substrates other than germanium substrates, and the preparation methods are not limited to the content disclosed in the embodiments. All equal changes and modifications made according to the claims of the present invention shall belong to the scope of the present invention. coverage.

Claims (6)

1. a surface passivation method of germanium base substrate, its step comprises: 1) Clean the surface of the germanium substrate to remove surface contamination and natural oxide layer; 2) Put the germanium substrate into the plasma chamber; 3) Use the reactive gas corresponding to the multi-bond atoms to generate plasma and perform plasma bath treatment on the germanium substrate; 4) Deposit gate dielectric; 5) Subsequent processes are performed to prepare MOS capacitors or devices. 2. the surface passivation method of germanium base substrate as claimed in claim 1, is characterized in that, described step 1) in, germanium substrate substrate is bulk Ge substrate, GOI substrate or any surface contains Ge epitaxy layer of substrate. 3. The method for surface passivation of a germanium-based substrate according to claim 1, wherein the plasma chamber in step 2) is an inductively coupled plasma chamber, or other chambers capable of generating plasma. 4. The surface passivation method for germanium-based substrates according to claim 1, wherein the reaction gas in step 3) is an elemental gas corresponding to a multi-bond atom; or the reaction gas is hydrogenation containing a multi-bond atom or the reaction gas is a mixed gas of an elemental gas corresponding to a multi-bond atom and an inert atomic gas; or the reaction gas is a mixed gas of a hydride containing a multi-bond atom and an inert atomic gas. 5. The surface passivation method for germanium-based substrates according to claim 1, wherein, in the step 3), when the reaction gas is an elemental gas corresponding to a multi-bond atom or a hydride containing a multi-bond atom, The flow rate of the gas is 5~100sccm; for the reaction gas is a mixed gas of the elemental gas corresponding to the multibond atoms and the inert atomic gas, the flow rate of the elemental gas corresponding to the multibond atoms is 5~100sccm, and the flow rate of the inert atomic gas 2~100sccm; for the case where the reaction gas is a mixed gas of a hydride containing multibond atoms and an inert atomic gas, the flow rate of the hydride containing multibond atoms is 5~100sccm, and the flow rate of the inert atomic gas is 2~100sccm . 6. the surface passivation method of germanium-based substrate as claimed in claim 1, is characterized in that, the pressure of reaction gas in described step 3) is 8～200mTorr, and the power for generating plasma is 20～1500W, The plasma bath treatment time is 5s~60min.

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