WO2011055671A1 - Film forming method and method for forming capacitor - Google Patents

Abstract

Disclosed is a film forming method which comprises: a step wherein a starting material gas containing titanium and a nitrogen-containing gas are supplied onto a substrate to be processed in a process chamber and a titanium nitride film is formed on the substrate to be processed by a heat treatment; and a step wherein the titanium nitride film is subjected to a plasma treatment by which the stress of the film is reduced.

Description

Film forming method and capacitor forming method

The present invention relates to a film forming method for forming a thin film on the surface of a semiconductor wafer or the like and a capacitor forming method.

In general, in order to form a semiconductor integrated circuit such as an IC, a desired transistor element is formed by repeatedly performing film formation, etching, thermal diffusion, oxidation, etc. on the surface of a semiconductor wafer or glass substrate. In addition, resistance elements, capacitors, and the like are integrated and formed at a high density. In recent years, in particular, along with the high integration of semiconductor devices, the miniaturization of each element tends to further progress. For example, in a memory device such as a DRAM, the occupied area of each cell becomes smaller due to the trend toward miniaturization. However, in order to secure a sufficient capacitance value, the insulation layer between the capacitor electrodes can be secured even if the occupied area is reduced. It is sufficient to reduce the thickness or increase the dielectric constant of this dielectric. However, reducing the thickness of this insulating layer degrades the insulation, and various materials can be used to make the material high dielectric. There are currently technical problems.

Therefore, as a structure that can increase the capacitance of the capacitor even when the occupied area or the occupied volume is small, a capacitor structure in which the capacitor is formed into a cylindrical shape or a cylindrical shape has been proposed (for example, Patent Document 1). .

In addition, as an electrode used for the capacitor, a polysilicon film has been generally used. However, recently, a specific resistance value is relatively low even when miniaturized and the step coverage is excellent. For this reason, a titanium nitride film (TiN film) is being used. For example, a cylindrical capacitor in a DRAM memory cell includes a cylindrical lower electrode connected to a contact plug extending from one of source / drain regions formed on a main surface of a silicon substrate (semiconductor wafer) with a gate electrode interposed therebetween. And a high dielectric constant film such as HfO ₂ formed on the surface of the cylindrical lower electrode, and an upper electrode formed on the surface of the high dielectric constant film, and titanium nitride is used as the lower electrode and the upper electrode. A (TiN) film is used. A large number of cylindrical capacitors having such a structure are arranged in a matrix on the main surface of the Si substrate.

This titanium nitride film is formed by a thermal CVD (Chemical Vapor Deposition) method, which is a high step coverage film forming method, since it is necessary to sufficiently coat the fine cylindrical lower electrode. In the film formation of TiN by the thermal CVD method, for example, TiCl ₄ is used as a source gas, NH ₃ is used as a nitriding gas, and these are supplied onto a heated substrate to form a TiN film on the substrate. In addition, film formation is also performed by SFD (Sequential Flow Deposition) processing in which the step of supplying the source gas and the nitriding gas and the step of supplying only the nitriding gas are alternately performed with a purge interposed therebetween.

JP 2002-222871 A JP-T-2001-507514 JP 2004-263207 A

By the way, in general, in forming a TiN film, the specific resistance of the film decreases as the film forming temperature is increased. However, when the specific resistance decreases, the stress of the film increases. In other words, the specific resistance of the film and the stress of the film have a contradictory relationship, and a high-quality film having a high specific resistance increases the stress. In particular, a film having a very low specific resistance can be obtained by low-temperature film formation by SFD, but the stress of the film becomes particularly high.

When the film stress increases in this way, the entire wafer warps and the focus is shifted during photolithography, cracks and cracks occur in the cylindrical or cylindrical capacitor, and the wafer is caused by such warpage. Inconveniences such as insufficient clamping and electrostatic attraction of itself occur. Furthermore, there is a known structure in which adjacent cylindrical capacitors are connected by a support bar to maintain strength, but there is also a problem that the support bar is broken by stress of the TiN film.

Such a problem may also occur when another film such as a tungsten (W) film is formed by thermal CVD.

Therefore, an object of the present invention is to provide a film forming method capable of forming a film with less stress on the surface of an object to be processed.
Another object of the present invention is to provide a capacitor forming method using the film forming method.

According to the first aspect of the present invention, a raw material gas containing titanium and a nitrogen-containing gas are supplied to a substrate to be processed in a processing vessel, and a titanium nitride film is formed on the substrate to be processed by heat treatment. There is provided a film forming method including performing a process for reducing a film stress caused by plasma on the titanium nitride film.

According to the second aspect of the present invention, the first step of forming a titanium nitride film on the substrate to be processed by supplying a raw material gas containing titanium and a nitrogen-containing gas to the substrate to be processed in the processing vessel and performing a heat treatment. And the second step of stopping the supply of the source gas and supplying the nitrogen-containing gas to nitride the titanium nitride film, and simultaneously generating plasma in the processing vessel to reduce the stress of the film A repeated film formation method is provided.

According to a third aspect of the present invention, a source gas containing tungsten and a reducing gas are supplied to a substrate to be processed in a processing container, and a tungsten film is formed on the substrate to be processed by heat treatment. There is provided a film forming method including performing a process for reducing a film stress caused by plasma on the film.

According to a fourth aspect of the present invention, there is provided a capacitor forming method for forming a capacitor on a surface of a substrate to be processed, wherein a plurality of recesses are formed on a surface of an insulating layer provided on the surface of the substrate to be processed. In addition, on the surface of the insulating layer including the surfaces in the plurality of recesses, a raw material gas containing titanium and a nitrogen-containing gas are supplied to the substrate to be processed in the processing vessel, and are nitrided on the substrate to be processed by heat treatment. Forming a first thin film made of a titanium nitride film using a film forming method including forming a titanium film and subjecting the titanium nitride film to a treatment for reducing film stress caused by plasma; Removing the first thin film on the surface of the insulating layer so as to leave the first thin film on the surface in a plurality of recesses, and removing the insulating layer to form the first thin film in a cylindrical shape Leave as a protrusion And forming a high dielectric constant film on the entire surface including the surface of the remaining cylindrical projection, and treating the surface of the high dielectric constant film with a raw material gas containing nitrogen and a nitrogen-containing gas. Forming a titanium nitride film on a substrate to be processed by supplying heat to the substrate to be processed in a container and performing a treatment for reducing the stress of the film due to plasma on the titanium nitride film To form a second thin film made of a titanium nitride film, and to etch away the second thin film and the high dielectric constant film remaining between the plurality of cylindrical projections. Forming a plurality of electrically separated capacitors is provided.

It is a schematic plan view which shows the processing system as an example of the apparatus for enforcing the method of this invention. It is a block diagram which shows the 1st processing apparatus for forming the TiN film | membrane mounted in the processing system of FIG. It is a block diagram which shows the 2nd processing apparatus for performing the process which reduces the stress of the film | membrane by the plasma mounted in the processing system of FIG. It is a flowchart which shows each process of the film-forming method of this invention performed with the processing system of FIG. It is a figure which shows an example of the timing chart at the time of forming the TiN film | membrane by SFD method. It is an X-ray diffraction profile showing a diffraction peak position of TiN (200) of an as-deposited TiN film. It is a schematic diagram which shows the state of the crystal lattice of the as-deposited TiN film. It is a X-ray diffraction profile which shows the diffraction peak position of TiN (200) of the TiN film which performed the plasma processing after film-forming. It is a schematic diagram which shows the state of the crystal lattice of the TiN film which performed the plasma processing after film-forming. It is a schematic diagram which shows the state of the crystal | crystallization of the TiN film | membrane as-deposited (as depo). It is a schematic diagram which shows the state of the crystal | crystallization of the TiN film | membrane which performed plasma processing after film-forming. It is a figure which shows the stress of the wafer radial direction of the TiN film | membrane which was formed into a film by SFD (as depo), and the TiN film | membrane which performed the plasma processing after film-forming. It is a figure which shows the relationship between temperature and the specific resistance of a film about the TiN film | membrane formed into various conditions as what is formed into a film (as depo), and what performed plasma treatment after that. It is a figure which shows the relationship between the temperature and the stress of a film | membrane about the TiN film | membrane formed into a film under various conditions as-deposited (as depo), and the thing which performed plasma processing after that. It is a figure which shows the relationship between the specific resistance of a film | membrane, and the stress of a film | membrane about what was formed into a film (as depo) about the TiN film | membrane formed on various conditions, and what performed plasma treatment after that. It is a figure which shows the relationship between processing time and specific resistance at the time of performing plasma processing by changing processing time after forming a TiN film by SFD. It is a figure which shows Cl density | concentration of the depth direction after performing 30 sec plasma processing as it is in a film-forming (as depo). It is a figure which shows O density | concentration of the depth direction after performing a plasma process for 30 second as a film-forming (as depo). It is a figure which shows the various process conditions and measurement result when forming a TiN film | membrane with the method of this invention and the conventional method. It is a figure which shows the various process conditions and measurement result when forming a TiN film | membrane with the method of this invention and the conventional method. It is a figure which shows the various process conditions and measurement result when forming a TiN film | membrane with the method of this invention and the conventional method. It is sectional drawing which shows the processing apparatus as another example of the apparatus for enforcing the method of this invention. It is a figure which shows the various process conditions and measurement result when performing this invention method. It is a figure which shows an example of the timing chart of the film-forming method which performs the stress reduction process by a cycle plasma, when forming a TiN film | membrane by SFD method in the apparatus of FIG. It is a figure which compares and shows the specific resistance of the TiN film | membrane in what formed the plasma treatment after as-deposition (as depo), and what performed SFD + cycle plasma on four conditions. It is a figure which compares and shows the stress of the TiN film | membrane in what carried out SFD + cycle plasma on four conditions as what was formed into a film (as depo), and after that plasma-processed. It is a flowchart which shows an example of the formation method of the capacitor provided with the TiN film | membrane formed into a film using the method of this invention as an electrode. It is process sectional drawing which shows each process in an example of the formation method of the capacitor provided with the TiN film | membrane formed using the method of this invention as an electrode. It is a top view of (E) of FIG. It is sectional drawing which shows an example of the element carrying the capacitor provided with the TiN film | membrane formed using the method of this invention as an electrode.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

<An example of an apparatus for carrying out the method of the present invention>
First, an example of an apparatus for carrying out the method of the present invention will be schematically described. FIG. 1 is a schematic plan view showing a processing system as an example of an apparatus for carrying out the method of the present invention. As shown in FIG. 1, the processing system 10 includes first and second processing apparatuses 12 and 14 and a substantially hexagonal common transfer chamber 16 as main components. In addition, the processing system 10 includes first and second load lock chambers 18A and 18B having a load lock function, and an introduction-side transfer chamber 20 having an elongated shape. Specifically, the first and second processing devices 12 and 14 are connected to two sides of the substantially hexagonal common transfer chamber 16 respectively, and the first and second load locks are respectively connected to the two opposite sides. The chambers 18A and 18B are connected.

Gate valves G are interposed between the common transfer chamber 16 and the first and second processing devices 12 and 14 and between the common transfer chamber 16 and the first and second load lock chambers 18A and 18B, respectively. Being a cluster tool. These gate valves G can communicate and block between the first and second processing apparatuses 12 and 14 and the common transfer chamber 16, and between the first and second load lock chambers 18A and 18B and the common transfer chamber 16. It has become. A gate valve G is similarly interposed between the first and second load lock chambers 18A and 18B and the introduction-side transfer chamber 20, as will be described later. The first and second load lock chambers 18A and 18B can selectively realize a vacuum atmosphere and an atmospheric pressure atmosphere as the semiconductor wafer W as the object to be processed is loaded and unloaded. The inside of the common transfer chamber 16 is maintained in a vacuum atmosphere.

In the common transfer chamber 16, an articulated arm that can bend and extend and pivot to a position where the first and second load lock chambers 18 </ b> A and 18 </ b> B and the first and second processing devices 12 and 14 can be accessed. A transport mechanism 22 having a structure is provided. The transport mechanism 22 has two picks A1 and A2 that can bend and stretch independently in opposite directions, and can handle two wafers at a time.

The introduction-side transfer chamber 20 is formed by a horizontally long box, and one or more, 3 in the illustrated example, for introducing a semiconductor wafer as an object to be processed is formed on one side of the opposing long sides. One carry-in entrance is provided, and an open / close door 24 that can be opened and closed is provided at each carry-in entrance. An introduction port 26 is provided corresponding to each of the carry-in ports, and one substrate container 28 can be placed on each introduction port 26. The substrate container 28 can accommodate a plurality of, for example, 25 wafers W stacked in multiple stages at an equal pitch. A clean air downflow is formed in the introduction-side transfer chamber 20, and the atmosphere is set to a pressure of about atmospheric pressure.

In the introduction side transfer chamber 20, an introduction side transfer mechanism 30 for transferring the wafer W along the longitudinal direction thereof is provided. The introduction-side transport mechanism 30 is slidably supported on a guide rail (not shown) provided to extend along the length direction in the introduction-side transport chamber 20. The introduction-side transport mechanism 30 has two arms 30A and 30B that can be bent and stretched. At one end of the introduction-side transfer chamber 20, an orienter 32 for aligning the wafer is provided. The positioning notch of the wafer W, for example, the position direction of the notch or the orientation flat or the position of the center of the wafer W is provided. The amount of deviation can be detected.

The first and second load lock chambers 18A and 18B are connected via the gate valve G to the other side of the opposing long side of the introduction-side transfer chamber 20. In each of the first and second load lock chambers 18A and 18B, a table 32 having a diameter smaller than the wafer diameter is installed to temporarily place the wafer W, and an atmospheric pressure atmosphere is provided therein. In this state, the wafer W can be carried in and out using the introduction side transfer mechanism 30.

The processing system 10 has a system control unit 34 composed of a computer for controlling the operation of the entire processing system. The system control unit 34 controls loading and unloading operations of the semiconductor wafer W, specific operations of the first and second processing apparatuses 12 and 14, and the like. The system control unit 34 is connected to a storage unit 36 having a storage medium for storing a computer-readable program necessary for these operations and operations. The storage medium may be a fixed medium such as a hard disk or a portable medium such as a flexible disk, a CD-ROM, a DVD, or a flash memory.

Next, the first processing apparatus 12 will be described with reference to FIG. The first processing apparatus 12 is an apparatus that forms a titanium nitride (TiN) film as a thin film by thermal CVD or SFD. As shown in FIG. 2, the first processing apparatus 12 includes a processing container 40 formed as a cylindrical box body, for example, from an aluminum alloy or the like. In the processing container 40, a mounting table 44 is provided which is erected from the bottom by a support 42. A semiconductor wafer W having a diameter of, for example, 300 mm is mounted on the upper surface of the mounting table 44.

The mounting table 44 is provided with elevating pins (not shown) that support the lower surface of the wafer W when the wafer W is loaded and unloaded. Further, a resistance heater 46 is provided over the entire surface of the mounting table 44 as a heating means for heating the wafer W. In addition, a loading / unloading port 49 is provided on one side of the processing container 40, and the common transfer chamber 16 is connected to the loading / unloading port 49 via a gate valve G so that the wafer W can be loaded / unloaded. It has become.

A shower head 50 as a gas introduction unit is provided on the ceiling of the processing container 40. The shower head 50 has a large number of gas discharge holes 48A and 48B on the lower surface. Separately divided diffusion chambers 52A and 52B are formed in the shower head 50, and the gas discharge holes 48A are diffused. The gas discharge hole 48B communicates with the diffusion chamber 52B. Gases are separately supplied to the diffusion chambers 52A and 52B via gas supply pipes 51A and 51B, respectively. Here, TiCl ₄ gas is used as a source gas, NH ₃ gas is used as a nitrogen-containing gas, TiCl ₄ gas is introduced into the diffusion chamber 52A via one gas supply pipe 51A, and NH ₃ gas is the other gas. The gas is introduced into the diffusion chamber 52B through the supply pipe 51B and discharged into the processing container 40 from the gas discharge holes 48A and 48B, respectively.

Further, N ₂ gas is also supplied as an additive gas to both the diffusion chambers 52A and 52B. Although not shown, each gas is supplied while its flow rate is controlled by a flow controller such as a mass flow controller, and the start and stop of the supply are also controlled by an on-off valve. With these gases, a TiN film can be formed by thermal CVD or SFD without using plasma.

Further, an exhaust port 54 is provided at the bottom of the processing vessel 40, and a vacuum exhaust system 56 is connected to the exhaust port 54. The vacuum exhaust system 56 has an exhaust passage 58 connected to the exhaust port 54, and a pressure regulating valve 60 and a vacuum pump 62 are sequentially provided in the exhaust passage 58, so The atmosphere can be evacuated while adjusting the pressure. In addition, each component of the first processing device 12 is operation-controlled by a command from the system controller 34 described above.

Next, the second processing apparatus 14 will be described with reference to FIG. FIG. 3 is a block diagram showing the second processing apparatus. The second processing apparatus 14 is an apparatus for reducing the stress of the film by performing a plasma process on the TiN film formed by the first processing apparatus 12. As shown in FIG. 3, the second processing apparatus 14 has a processing container 70 formed into a cylindrical shape by, for example, an aluminum alloy, and the processing container 70 is grounded.

An exhaust port 72 for exhausting the atmosphere in the container is provided at the bottom of the processing container 70, and a vacuum exhaust system 74 is connected to the exhaust port 72. The evacuation system 74 has an exhaust passage 76 connected to the exhaust port 72. The exhaust passage 76 has a valve opening degree for adjusting the pressure from the upstream side to the downstream side. An adjustable pressure regulating valve 78 and a vacuum pump 80 are sequentially provided. Thereby, the inside of the processing container 70 can be evacuated uniformly from the bottom peripheral portion.

In the processing container 70, a disk-like mounting table 82 is provided on which a semiconductor wafer W having a diameter of 300 mm, for example, is mounted via a support 81 made of a conductive material. Specifically, the mounting table 82 is made of a conductive material such as an aluminum alloy, and also functions as a lower electrode that is one of plasma electrodes. This lower electrode is grounded. As the lower electrode, for example, a mesh-like conductive member may be embedded in a member made of ceramic such as AlN, and this conductive member may be grounded.

In the mounting table 82, for example, a resistance heater 84 is embedded as a heating means, so that the semiconductor wafer W can be heated and maintained at a desired temperature. In addition, the mounting table 82 presses the peripheral portion of the semiconductor wafer W and fixes it on the mounting table 82, or a clamping ring (not shown), and the semiconductor wafer W is pushed up and down when the semiconductor wafer W is loaded / unloaded. A lifter pin is provided.

A shower head 86 as a gas introducing means functioning as an upper electrode which is the other of the plasma electrodes is provided on the ceiling portion of the processing container 70, and this shower head 86 is provided integrally with the ceiling plate 88. ing. The peripheral portion of the ceiling plate 88 is airtightly attached to the upper end portion of the container side wall via an insulating material 90, and the shower head 86 and the processing container 70 are insulated. The shower head 86 is made of a conductive material such as an aluminum alloy. A large number of gas discharge holes 92 for discharging gas are formed on the lower surface of the shower head 86. A gas supply pipe 93 is connected to the upper surface of the shower head 86.

A plasma generation gas is supplied to the shower head 86 via a gas supply pipe 93. As the plasma generation gas, N ₂ gas, H ₂ gas, NH ₃ gas, or a rare gas can be suitably used, and at least one of these can be used. Ar gas is suitable as the rare gas. Although not shown, the plasma generation gas is supplied while being controlled in flow rate by a flow rate controller such as a mass flow controller, and the start and stop of the supply are also controlled by an on-off valve.

A high frequency power source 98 is connected to the shower head 86 via a feeder line 94 as a plasma generation mechanism for generating plasma in the processing space S between the mounting table 82 and the shower head 86. A matching circuit 96 is provided in the middle of the feeder line 94. As the high frequency power source 98, for example, a power source having a frequency of 450 kHz can be used. Here, the mounting table 82 is grounded and high frequency power is applied to the shower head 86. However, the present invention is not limited to this, and contrary to the above, high frequency power is applied to the mounting table 82 and the shower head 86 is grounded. You may make it do.

Further, a loading / unloading port 100 for loading / unloading the semiconductor wafer W is provided on the side wall of the processing container 70, and a gate valve G that can be opened and closed airtightly when loading / unloading the semiconductor wafer W is provided in the loading / unloading port 100. Provided. Note that each component of the second processing device 14 is controlled in accordance with a command from the system controller 34 described above.

<Example of film forming method by processing system 10>
Next, a film forming method of the present invention performed using the processing system 10 formed as described above will be described with reference to FIG. FIG. 4 is a flowchart showing each step of the film forming method according to the present embodiment. First, an unprocessed semiconductor wafer W is taken into the interior from the substrate container 28 placed on the introduction port 26 of the introduction side transfer chamber 20 by using the introduction side transfer mechanism 30, and this semiconductor wafer W is transferred to the orienter 32. Perform alignment. The aligned wafer W is again carried into one of the first and second load lock chambers 18A and 18B by the introduction-side transfer mechanism 30.

The wafer W in the load lock chamber is adjusted in pressure in the load lock chamber, and then taken into the common transfer chamber 16 that has been previously maintained in a vacuum atmosphere by the transfer mechanism 22 in the common transfer chamber 16. The wafer W is first carried into the first processing apparatus 12 and a film forming process is performed (step 1). The wafer W after the film forming process is then carried into the second processing apparatus 14. Then, a process for reducing the stress of the film by the plasma process is performed (step 2). Then, the processed wafer W after the completion of each process follows the path opposite to the above-described path and is accommodated in the substrate container 28 that accommodates the processed wafer W.

Next, the film forming process of process 1 performed in the first processing apparatus 12 shown in FIG. 2 will be described. Here, it is necessary to use a film formation method with good step coverage in consideration of film formation in a cylindrical shape or a cylindrical shape such as a capacitor electrode of a DRAM. For this reason, a source gas and a nitridation method are used without using plasma. A TiN film is formed by heat using a gas. Incidentally, the height of the lower electrode in a cylindrical or cylindrical capacitor of DRAM is about 2 to 3 μm, and its aspect ratio is about 20 to 30. As a specific processing method, a simple thermal CVD method for forming a TiN film on a substrate heated by simultaneously flowing a raw material gas and a nitriding gas, a step of supplying the raw material gas and the nitriding gas, and only the nitriding gas are included. An SFD method, which is a thermal CVD method in which a film is formed by alternately flowing the supplying steps, or a film is formed by alternately flowing a source gas and a nitriding gas, can be preferably used. Among these, the SFD method that can form a high-quality film with a relatively low temperature, less impurities, and a small specific resistance is preferable.

Hereinafter, the formation of the TiN film by the SFD method will be described in detail.
In the film formation by the SFD method, basically, as described above, TiCl ₄ gas as a source gas and NH ₃ gas as a nitriding gas are intermittently and repeatedly flowed, and N ₂ gas is supplied to these gases as necessary. Add as appropriate. FIG. 5 is a diagram showing an example of a timing chart when a TiN film is formed by the SFD method. As shown in FIG. 5, a step S1 of forming a thin film by flowing a TiCl ₄ gas as a source gas and an NH ₃ gas as a nitriding gas for a predetermined time, and a thin film by stopping the supply of TiCl ₄ and flowing NH ₃ Step S2 for nitriding the film is alternately repeated with step S3 being a purge process, to form a TiN film having a predetermined thickness. Each step S1 and step S2 is one cycle, and the number of cycles is set according to the target film thickness. In addition, step 3 which is a purge process is not essential.

At this time, TiCl ₄ gas is introduced into the processing vessel 40 from the gas discharge hole 48A of the shower head 50 through the gas supply pipe 51A, and NH ₃ gas is introduced into the gas discharge hole 48B of the shower head 50 through the gas supply pipe 51B. Are introduced into the processing container 40. Further, the pressure in the processing vessel 40 is maintained at a predetermined process pressure by evacuation by the vacuum exhaust system 56. The wafer W placed on the mounting table 44 is maintained at a predetermined temperature by the resistance heater 46. Instead of the above sequence, a sequence in which TiCl ₄ gas and NH ₃ gas are alternately supplied with a purge interposed therebetween may be employed. In this case, first, TiCl ₄ gas is adsorbed on the surface of the wafer W by supplying TiCl ₄ gas, and then TiCl ₄ adsorbed by supplying NH ₃ gas is nitrided to form TiN, This is repeated until a desired film thickness is obtained, and a TiN film is formed.

The process conditions at the time of this SFD are exemplified as follows.
Process temperature: 250-1000 ° C
Process pressure: 13 to 1330 Pa
TiCl ₄ gas flow rate: 10-100 sccm
NH ₃ gas flow rate: 10 to 5000 sccm
N ₂ gas flow rate: 100-5000sccm
TiN film thickness: 1-100nm

By this film formation process, as described above, a TiN film can be formed up to the inner surface in the recess having a large aspect ratio, and film formation with good step coverage can be performed. Note that the supply mode of each gas is merely an example, and any known gas supply mode may be used. When performing simple thermal CVD, the raw material gas, TiCl ₄ gas, the nitriding gas, NH ₃ gas, and optionally N ₂ gas may be supplied simultaneously under the same conditions.

Next, a description will be given of the stress reduction process using plasma in process 2 performed in the second processing apparatus 14 shown in FIG. Here, a plasma process is performed on the TiN film formed by the first processing apparatus 12 to reduce the stress of the TiN film.

Conventionally, in the formation of a TiN film by a thermal CVD method, in order to obtain a high quality film with low impurities such as Cl and low specific resistance, the film formation temperature has been increased, and the high specific resistance is low. In order to obtain the film at a relatively low temperature, film formation by the SFD method has been proposed, but it has been found that the stress of the TiN film increases as the specific resistance decreases by these methods. FIG. 6 shows an X-ray diffraction profile of the TiN film as it is formed. As shown in FIG. 6, it can be seen that the peak position of TiN (200) is shifted to a higher angle side than the peak position of bulk TiN. It was also found that the as-deposited TiN film had a lattice constant of 0.421 nm, which was smaller than the lattice constant of bulk TiN, 0.424 nm. That is, when a TiN film is formed by thermal CVD, a large amount of impurities such as Cl escape from the film, which causes distortion in the crystal lattice as shown in FIG. Presumed to occur.

Therefore, by performing plasma treatment after forming the TiN film, the distortion of the crystal lattice is alleviated and the stress of the film is reduced. FIG. 8 shows an X-ray diffraction profile of the TiN film after the plasma treatment. As shown in this figure, the peak position of TiN (200) is substantially coincident with the peak position of bulk TiN, and the lattice constant is also shown. The value is 0.423 nm, which is close to 0.424 nm which is the lattice constant of bulk TiN, and as shown in FIG. 9, it is confirmed that the distorted portion of the crystal lattice spreads and the distortion of the film is relaxed.

To explain this at the crystal level, as shown in FIG. 10, the TiN crystal grown in a columnar shape is distorted and unstable crystals are seen as shown in FIG. As shown in FIG. 11, the distortion of the crystal is relaxed and the unstable crystal is also stabilized, thereby reducing the stress of the film. At this time, impurities such as chlorine existing in the film are reduced by the plasma treatment, and a film with higher quality is obtained. Further, the tip of the TiN crystal is etched by the plasma treatment, and the surface roughness of the TiN film is reduced.

When performing the stress reduction process using plasma in process 2, the plasma generation gas is supplied into the processing container 70 of the second processing apparatus 14 through the shower head 86 while controlling the flow rate. Is maintained at a predetermined pressure while being evacuated by the evacuation system 74, the wafer W placed on the mounting table 82 is maintained at a predetermined temperature by the resistance heater 84, and the shower head 86 is supplied from the high frequency power source 98. Is applied with high frequency power to generate plasma in the processing space S between the mounting table 82 and the shower head 86.

As long as the plasma treatment is a gas that does not adversely affect the film, any gas species can be used. However, as described above, N ₂ gas, H ₂ gas, NH ₃ gas, and a rare gas can be suitably used. At least one of them can be used. Since the effect can be obtained with only a rare gas, the stress reduction action is not caused by a chemical reaction, but is considered to be an action of ions in plasma. Ar gas is suitable as the rare gas. As the plasma generation gas, for example, both or one of NH ₃ gas and H ₂ gas and Ar gas can be suitably used.

Examples of the process conditions for this plasma treatment include the following.
Process temperature: 250-1000 ° C
Process pressure: 13 to 1330 Pa
High frequency power: 100-1500 watts (W)
Plasma generating gas: Ar, H ₂ , NH ₃
Gas flow rate: Ar gas 100-5000sccm
H ₂ gas 100-5000sccm
NH ₃ gas 100-5000sccm
Process time: 1 to 300 sec

When the process temperature is lower than 250 ° C., the effect of reducing the stress due to plasma cannot be sufficiently achieved. When the process temperature is higher than 1000 ° C., the characteristics of the underlying element formed in the previous process on the wafer W deteriorate. End up. The preferred range of process temperature is 300-850 ° C. Further, when the process time is less than 1 sec, the effect of the plasma treatment cannot be sufficiently exhibited. When the process time is longer than 300 sec, the effect of the plasma treatment is saturated, resulting in a decrease in throughput.

As a result of reducing the stress of the TiN film by this plasma treatment, various problems caused by the stress of the TiN film can be solved. For example, not only can the warpage of the semiconductor wafer itself be reduced to suppress a focus shift during photolithography, but also the wafer itself can be reliably clamped or attracted by an electrostatic chuck. Further, it is possible to prevent cracks and cracks in the lower electrode and the upper electrode in the cylindrical or cylindrical capacitor, or breakage of the support bar that supports them.

The result of actually measuring the stress of the TiN film is shown in FIG. Here, film formation is performed under three conditions of SFD of 5 cycles at 680 ° C. (condition A), 12 cycles of SFD at 480 ° C. (condition B), and 20 cycles of SFD at 400 ° C. (condition C). The stress was measured for the TiN films as they were deposited (as deposited) and for those films that were subjected to plasma treatment, and FIG. 12 shows the stress in the radial direction of the wafer. The plasma processing conditions at this time were Ar, H ₂ , and NH ₃ gases as plasma generation gases, high-frequency power power of 800 W, processing time of 120 sec, and temperature that were the same as those during the film forming process. As shown in this figure, it can be seen that the stress is reduced by performing the plasma treatment after the film formation. Among them, the tensile stress changes to the compressive stress under the high temperature condition A.

In addition, regarding the TiN film formed under various conditions, the film stress and specific resistance were measured for the as-deposited film and the plasma-treated film after that. The results are shown in FIGS. Note that the plasma treatment was performed under the same conditions as described above and at the same temperature as the film formation treatment. 13 is a diagram showing the relationship between temperature and specific resistance of the film, FIG. 14 is a diagram showing the relationship between temperature and film stress, and FIG. 15 is a diagram showing the relationship between specific resistance of film and stress.

As shown in FIG. 13, in the case of film formation, the specific resistance is extremely high at 460 ° C. in thermal CVD, but the specific resistance of the film is greatly reduced as the temperature is increased. In SFD, the specific resistance of the film is low even at a low temperature. However, the specific resistance decreases as the temperature rises. As shown in FIG. 14, the stress of the film at this time increases as the temperature increases, and as shown in FIG. 15, the stress of the film increases as the specific resistance decreases.

On the other hand, in the case of the plasma treatment, the stress decreased and the specific resistance also decreased, and it was confirmed that both the stress reduction and the specific resistance reduction can be achieved by performing the plasma treatment after the film formation process. In addition, about what performed SFD at 480 degreeC, it has changed from the tensile stress to the compressive stress by performing the plasma processing, but when the compressive stress is also disliked, the stress is changed by changing the conditions of the plasma processing. Can approach 0.

After forming a TiN film having a thickness of 12 nm by performing SFD at 680 ° C. for 30 cycles, Ar, H ₂ , and NH ₃ gases were used as plasma generation gases, high-frequency power was set to 800 W, and the temperature was changed during the film formation process. The change in specific resistance was grasped by changing the processing time to 680 ° C. The result is shown in FIG. As shown in this figure, it can be seen that the specific resistance rapidly decreases in the stage up to about 50 sec. FIG. 17A shows the Cl concentration in the depth direction after performing as-deposited (as depo) and 30 sec plasma treatment, and FIG. 17B shows the concentration in the depth direction after performing the as-deposited 30 sec plasma treatment. O concentration is shown. As shown in these figures, it was confirmed that the impurity concentration was reduced by performing plasma treatment after film formation.

As described above, the stress of the TiN film can be reduced by the plasma treatment. However, the required level of the film stress differs depending on the application, and not only the film stress is reduced but also the film stress is reduced. It is desirable to be able to control. Such stress on the TiN film can be controlled by adjusting the conditions in the plasma processing. Specifically, the stress of the film can be controlled relatively easily by changing the temperature or time of the plasma treatment.

In the above, an example in which the stress of the film after the TiN film is formed by thermal CVD (including SFD) is reduced by plasma processing has been described. However, the stress reduction process by such plasma processing is performed by thermal CVD. This is also effective when forming a film. Specifically, when a raw material gas, for example, WF6 gas, and a reducing gas, for example, H2 gas, are supplied onto a heated substrate to form a W film, stress is generated in the film. Also in this case, the stress can be reduced by plasma treatment.

<Evaluation 1 of the method of the present invention>
Next, the result of actually forming a TiN film and performing plasma processing using the film forming method of the present invention and measuring the characteristics thereof will be described in detail. FIG. 18 is a diagram showing various process conditions and measurement results when the method of the present invention is performed. Here, for comparison, the measurement results of the TiN film formed by the conventional film forming method are also shown.

Here, the conventional methods 1 to 4 and the inventive methods 1 to 4 were performed as described as run names in FIG. The TiN film is formed by using the SFD method here, and the number of repetitions is described as “cycle”. In the case of the conventional method, the characteristics of the TiN film itself formed by the SFD method are measured, and in the case of the method of the present invention, the characteristics are measured after the TiN film is further subjected to the plasma treatment characterized by the present invention. The conventional method and the method of the present invention having the same run name correspond to each other. In this evaluation 1, there are two types of process temperatures (set temperatures) during TiN film formation: 480 ° C. and 680 ° C. The process temperature (set temperature) during the plasma treatment is 450 ° C.

The difference between Method 1 and Method 2 is that Method 1 has 10 cycles, whereas Method 2 has a short cycle period and 32 cycles. The thickness is set to approximately the same thickness of about 7.5 to 8.2 nm. Also, the difference between the method 3 and the method 4 is that the period of one cycle is the same as each other, the number of cycles is changed to 13 and 6, and the film thicknesses formed corresponding to these are 24.7 to 26.3 nm and 12. The difference is 2 to 12.5 nm.

In the plasma treatment, all process pressures are 667 Pa, and all process times are 120 sec. The TiN film formed as described above was measured for film thickness, resistance (Rs), stress, and specific resistance (Rv), and the average value (Ave.) of each was obtained.

As is clear from FIG. 18, when the conventional method 1 and the method 1 of the present invention are compared, the resistance is 937.5Ω to 278.0Ω although the film thickness is substantially the same as 7.5 nm and 7.4 nm. And the specific resistance is also greatly reduced from 703.9 μΩcm to 207.0 μΩcm. Furthermore, the stress is greatly reduced from 1.4 GPa to −0.1 GPa, and it can be seen that the stress is almost zero and the method 1 of the present invention shows good results.

When comparing the conventional method 2 and the method 2 of the present invention, the period of one cycle is shortened and the number of cycles is increased as compared with the case of the method 1, and as a result, the film thickness is made substantially the same as the method 1. . In this case, the same result as in the case of the method 1 is obtained.

That is, when the conventional method 2 is compared with the method 2 of the present invention, although the film thickness is the same as 8.2 nm, the resistance is considerably reduced from 456.5Ω to 273.9Ω and the specific resistance is also 372. It is reduced from .9 μΩcm to 225.5 μΩcm. The stress is also greatly reduced from 1.8 GPa to −0.9 GPa, and it can be seen that the method 2 of the present invention shows good results.

Next, when the conventional method 3 and the method 3 of the present invention are compared, although the film thickness is substantially the same as 24.7 to 26.3 nm, the resistance is considerably reduced from 47.1Ω to 35.9Ω. In addition, the specific resistance is considerably reduced from 116.2 μΩcm to 94.5 μΩcm. Furthermore, it can be seen that the stress is greatly reduced from 2.1 GPa to 0.8 GPa, the stress is substantially zero, and Method 3 of the present invention shows good results.

Next, when the conventional method 4 and the method 4 of the present invention are compared, although the film thickness is substantially the same as 12.2 nm and 12.5 nm, the resistance is considerably reduced from 121.4Ω to 83.2Ω. However, the specific resistance is considerably reduced from 148.0 μΩcm to 103.8 μΩcm. In addition, the stress is greatly reduced from 1.9 GPa to −0.1 GPa, and it can be seen that the stress is almost zero and the method 4 of the present invention shows a good result.

As described above, it was confirmed that the stress of the thin film formed on the surface of the object to be processed can be reduced by the method invention.

<Evaluation 2 of the method of the present invention>
FIG. 19 is a diagram showing various process conditions and measurement results when the method of the present invention is performed. Here, for comparison, the measurement results of the TiN film formed by the conventional film forming method are also shown. The arrow “←” shown in FIG. 19 indicates the same value as the numerical value on the left side.

Here, as shown as run names in FIG. 19, the conventional methods 5 to 8 and the inventive methods 5 to 8 were performed. Here, all the TiN films are formed using the SFD method, and the number of repetitions is 13 as described as “cycle”. In the case of the conventional method, the characteristics of the TiN film itself formed by the SFD method are measured, and in the case of the method of the present invention, the characteristics are measured after the TiN film is further subjected to the plasma treatment characterized by the present invention. The conventional method and the method of the present invention having the same run name correspond to each other. In this evaluation 2, the process temperature (set temperature) during TiN film formation is 680 ° C. The process temperature (set temperature) during the plasma treatment is 640 ° C.

The difference between the method 5 and the method 6 and the difference between the method 7 and the method 8 are that, in the methods 5 and 7, the hydrogen-containing gas at the time of plasma treatment is NH ₃ gas and H ₂ gas, whereas the method 6 and 8 Then, the hydrogen-containing gas is H ₂ gas (in FIG. 19, the flow rate of NH ₃ in the plasma treatment is zero). Further, the difference between the methods 5 and 6 and the methods 7 and 8 is that the methods 5 and 6 are plasma processed in situ, and the methods 7 and 8 are plasma processed in ex situ. Here, “Insitu” means that the film forming process and the plasma process are continuously performed in a vacuum, and “Exitu” means that after the film forming process is performed, the wafer is once exposed to the atmosphere, and then the plasma process is performed again in a vacuum. That means. The plasma treatment of the above-described inventive methods 1 to 4 is performed in situ.

In the plasma treatment, all process pressures are 667 Pa, and all process times are 120 sec. For the TiN film formed as described above, the film thickness, resistance (Rs), stress, and specific resistance (Rv) were measured, and the value at the center of each semiconductor wafer W was obtained.

When comparing the conventional method 5 and the method 5 of the present invention, although the film thickness is substantially the same as 10.3 nm and 10.4 nm, the resistance is considerably reduced from 139.7Ω to 79.3Ω, The specific resistance is also considerably reduced from 145.0 μΩcm to 81.5 μΩcm. Moreover, the stress is greatly reduced from 1.8 GPa to −0.4 GPa, and it can be seen that the method 5 of the present invention shows good results.

Next, when the conventional method 6 and the method 6 of the present invention are compared, although the film thickness is substantially the same as 10.3 nm and 10.4 nm, the resistance is considerably reduced from 139.7Ω to 87.0Ω. In addition, the specific resistance is considerably reduced from 145.0 μΩcm to 92.8 ″ μΩcm. Moreover, the stress is greatly reduced from 1.8 GPa to −0.6 GPa, and the method 6 of the present invention is good. It turns out that the result is shown.

When comparing the conventional method 7 and the method 7 of the present invention, although the film thickness is substantially the same as 10.4 nm and 10.6 nm, the resistance is considerably reduced from 139.7Ω to 93.0Ω, The specific resistance is also considerably reduced from 145.0 μΩcm to 98.6 μΩcm. Moreover, the stress is greatly reduced from 1.8 GPa to −0.7 GPa, and it can be seen that the method 7 of the present invention shows good results.

When the conventional method 8 is compared with the method 8 of the present invention, the resistance is considerably reduced from 139.7Ω to 80.3Ω and the specific resistance is 145. despite the film thickness being the same as 10.4 nm. It is considerably reduced from 0 μΩcm to 83.1 μΩcm. Moreover, the stress is greatly reduced from 1.8 GPa to −0.4 GPa, and it can be seen that the method 8 of the present invention shows good results.

Thus, it was confirmed that the stress of the TiN film can be reduced even if the gas composition and the processing method are different in the plasma processing.

Further, it was confirmed that the process temperature during the plasma treatment can be surely exhibited in the temperature range from 450 ° C. of the present invention methods 1 to 4 to 640 ° C. of the present method 5 to 8.

<Evaluation 3 of the method of the present invention>
Next, an evaluation result obtained by performing plasma processing on a tungsten (W) film, which is a refractory metal similar to Ti, using the film forming method of the present invention and measuring its characteristics will be described. FIG. 20 is a diagram showing various process conditions and measurement results when the method of the present invention is performed. Here, for comparison, the measurement result of the W film formed by the conventional film forming method is also shown. Note that an arrow “←” shown in FIG. 20 indicates the same value as the numerical value on the left side.

Here, the conventional methods 9 to 10 and the inventive methods 9 to 10 were performed as described as run names in FIG. Here, the W film is formed using a thermal CVD method in which WF ₆ gas is used as a source gas, H ₂ gas is used as a reducing gas, Ar gas is used as a dilution gas, and all gases are simultaneously supplied to obtain a predetermined film thickness. Yes. In the case of the conventional method, the characteristics of the W film itself formed by the thermal CVD method are measured, and in the case of the method of the present invention, the characteristics are measured after the W film is further subjected to the plasma treatment which is the feature of the present invention. . The conventional method and the method of the present invention having the same run name correspond to each other. The process temperature (set temperature) during W film formation is 450 ° C., and the process temperature (set temperature) during plasma processing is also 450 ° C.

Further, the difference between the method 9 and the method 10 is that in the method 9, the hydrogen-containing gas is NH ₃ gas and H ₂ gas, whereas in the method 10, the hydrogen-containing gas is H ₂ gas (in FIG. The NH ₃ flow rate of the treatment is zero).

In the plasma treatment, all process pressures are 667 Pa, and all process times are 120 sec. For the W film formed as described above, the film thickness, resistance (Rs), stress, and specific resistance (Rv) were measured, and the value at the center of each wafer W was obtained.

When the conventional method 9 and the method 9 of the present invention are compared, the film thickness is the same as 46.3 nm, the resistance is slightly increased from 2847.5Ω to 3178.5Ω, and the specific resistance is from 13.2 μΩcm to 14 The same tendency toward 7 μΩcm. However, the stress decreases from 1.2 GPa to 0.7 GPa, and it can be seen that the method 9 of the present invention shows good results.

Next, when the conventional method 10 and the method 10 of the present invention are compared, the film thickness is substantially the same as 46.4 nm and 46.6 nm, the resistance is both 2675.1Ω, and the specific resistance is also 12.4 μΩcm. And approximately the same as 12.5 μΩcm. However, the stress is reduced from 1.1 GPa to 0.8 GPa, and it can be seen that the method 10 of the present invention shows good results.

Thus, it was confirmed that the stress of the film can be reduced by performing the plasma treatment even in the case of the tungsten film formed by thermal CVD.

<Another example of apparatus for carrying out the method of the present invention>
Next, another example of an apparatus for carrying out the method of the present invention will be schematically described. Here, a processing apparatus capable of performing both a film forming process and a plasma stress reducing process in one processing container will be described. FIG. 21 is a sectional view showing a processing apparatus as another example of an apparatus for carrying out the method of the present invention. The processing apparatus 110 has a basic configuration similar to that of the processing apparatus 12 and is obtained by adding a plasma generation mechanism for generating plasma to the configuration. The same components as the processing apparatus 12 are denoted by the same reference numerals. Description is omitted.

That is, on the ceiling of the processing container 40 of the processing apparatus 110, the high frequency power source 120 serves as a plasma generation mechanism for generating plasma in the processing space S ′ between the mounting table 44 and the shower head 50. Connected through. Therefore, the shower head 50 to which high frequency power is applied via the ceiling portion of the processing container 40 functions as an upper electrode. A matching circuit 124 is provided in the middle of the feeder line 122. As the high-frequency power source 120, for example, a power source having a frequency of 450 kHz can be used. On the other hand, the mounting table 44 is made of a ceramic member such as AlN, and the lower electrode 130 made of, for example, a mesh-like conductive member is embedded in the mounting table 44. An insulating material 131 is airtightly provided between the ceiling of the processing container 40 and the upper end of the side wall of the processing container 40, and the shower head 50 as the upper electrode and the processing container 40 are insulated. As the plasma generation gas, NH ₃ gas can be used, but as other plasma generation gas, H ₂ gas or Ar gas may be supplied through the gas supply pipe 51B. Here, the lower electrode 130 is grounded and high frequency power is applied to the shower head 50. However, the present invention is not limited to this, and conversely, the high frequency power is applied to the lower electrode 130 and the shower head 50 is grounded. You may make it do. Further, a resistance heater 46 is embedded as a heating means in the mounting table 44 so that the mounting table 44 can be controlled to a desired temperature.

<Example of film formation method by processing apparatus 110>
Next, a film forming method of the present invention performed using the processing apparatus 110 will be described.
Here, step 1 and step 2 in the flowchart of FIG. 4 can be performed in the processing container 40.

First, a simple thermal CVD method for forming a TiN film on a heated substrate by simultaneously flowing a source gas (for example, TiCl ₄ gas) and a nitriding gas (for example, NH ₃ gas), or supplying a source gas and a nitriding gas The step of forming the film by alternately flowing the step of performing and the step of supplying only the nitriding gas, or the concave portion of the wafer W by the SFD method which is the thermal CVD method of performing film formation by alternately flowing the source gas and the nitriding gas. Then, a TiN film is formed. The conditions at this time are the same as the conditions at the time of film formation in the first processing apparatus 12 described above.

Next, while the wafer W is mounted on the mounting table 44, the gas for film formation is stopped and the inside of the processing container 40 is purged, and then the plasma generation gas is supplied into the processing container 40 through the shower head 50. However, the inside of the processing vessel 40 is set to a predetermined pressure, and high frequency power is applied from the high frequency power source 120 to the shower head 50. As a result, plasma is generated in the processing space S ′ between the mounting table 44 and the shower head 50, and the wafer W is subjected to plasma processing. At this time, when the temperature at the time of the plasma processing is different from the temperature at the time of the film forming processing, the set temperature of the mounting table 44 is changed.

As the plasma generation gas, as in the case of the second processing apparatus 14 described above, N ₂ gas, H ₂ gas, NH ₃ gas, and rare gas can be suitably used, and at least one of these is used. be able to. If NH ₃ gas or N ₂ gas is used as the plasma generation gas, only the gas for film formation is sufficient, and there is no need to add a gas supply system for plasma generation. As in the case of the second film forming apparatus 14, when Ar gas is used with both or one of NH ₃ gas and H ₂ gas, it is necessary to add an Ar gas and H ₂ gas supply system.

The conditions for the plasma treatment are basically the same as those for the second processing apparatus 14 described above. Further, the TiN film after the plasma treatment has a reduced stress as in the case of the treatment by the second treatment apparatus 14.

In the processing apparatus 110, the TiN film forming process and the subsequent stress reduction process using plasma are performed in a lump without transferring the wafer W, so that the processing throughput can be increased. However, when the set temperature differs greatly between the film forming process and the plasma process, it takes time to change the temperature, and therefore the processing system 10 is more advantageous.

Next, another film forming method using the processing apparatus 110 will be described.
In this film forming method, plasma processing is performed simultaneously with the above-described SFD film forming. FIG. 22 is a diagram illustrating an example of a timing chart when plasma processing is performed simultaneously with film formation of SFD. As shown in FIG. 22, TiCl ₄ gas as a source gas and NH ₃ gas as a nitriding gas are allowed to flow for a predetermined time to form a thin film, and the supply of TiCl ₄ is stopped and NH ₃ is allowed to flow while high frequency is supplied. Step S12 in which high-frequency power is applied from the power source 120 to generate plasma to simultaneously perform nitriding and plasma processing is alternately repeated with step S13 being a purge step, thereby forming a TiN film having a predetermined thickness. . One step S11 and one step S12 are one cycle, and the number of cycles is set according to the target film thickness. The NH ₃ gas in step S12 serves both as a nitriding gas and a plasma generating gas. In addition, step 13 which is a purge process is not essential.

Instead of such a sequence, performing the steps of adsorbing the TiCl ₄ gas on the surface of the wafer W by supplying TiCl ₄ gas, nitriding to generate plasma while supplying NH ₃ gas and plasma treatment simultaneously You may employ | adopt the sequence which repeats a step until it becomes a desired film thickness.

According to such a film forming method, immediately after the thin TiN film is formed in step S11, the stress reduction process using plasma is performed on the film in step S12, and this process is repeated. It is possible to reduce the stress of the film and to obtain a film having a lower specific resistance. In addition, the stress of the TiN film can be controlled to a desired value by changing the plasma processing time and the number of cycles in step 12. A method of generating plasma cyclically in synchronism with the intermittent gas supply of SFD is also referred to as SFD + cycle plasma hereinafter.

Actually, the characteristics when the film is formed with such SFD + cycle plasma are compared with the case where the film is formed as it is (as depo) and the film is formed by performing the plasma treatment after the SFD described above (SFD + plasma treatment). explain. Here, the temperature at the time of basic SFD film formation is 480 ° C., and the conditions for the subsequent plasma processing are Ar, H ₂ , NH ₃ gas as plasma generation gas, high frequency power is 800 W, and processing time is The temperature was 480 ° C. for 5 seconds. The SFD + cycle plasma changes the time and the number of cycles in step 12 to 3 seconds × 10 cycles (condition 1), 3 seconds × 20 cycles (condition 2), 3 seconds × 30 cycles (condition 3), 10 seconds. X 30 cycles (condition 4). FIG. 23 shows the specific resistance of the TiN film formed under conditions 1 to 5 of as depo, SFD + plasma treatment, and SFD + cycle plasma, and FIG. 24 shows the stress. As shown in this figure, it can be seen that the SFD + cycle plasma which is the present film forming method has a lower resistance and higher stress reduction effect than the SFD + plasma treatment. It can also be seen that increasing the number of cycles or the processing time of step 12 further improves the effect of reducing specific resistance and the effect of reducing stress.

<Method for forming capacitor>
A capacitor forming method performed using the film forming method of the present invention will be described with reference to FIGS. FIG. 25 is a flowchart showing each step of the capacitor forming method according to the present invention, and FIG. 26 is a partially enlarged sectional view showing a part of the wafer in each step of the capacitor forming method. In FIG. 26, the lower structure formed on the semiconductor wafer W before forming the capacitor is omitted.

First, as shown in FIG. 26A, a contact 142 made of Ti or the like is formed in advance inside the semiconductor wafer W so as to correspond to a position where a capacitor is to be formed. A plurality (a large number) of contacts 142 are arranged in a matrix in two directions, for example, vertically and horizontally. An insulating layer 150 made of, for example, SiO ₂ is formed on the surface of the wafer W. In the middle of the insulating layer 150 in the thickness direction, a support bar insulating film 152 serving as a support bar is laminated so as to be embedded as described later. The support bar insulating film 152 is patterned in advance, for example, in a lattice pattern so as to intersect on the contact 142. The support bar insulating film 152 is made of a material different from that of the insulating layer 150, such as SiN.

The semiconductor wafer W is etched as shown in FIG. 26B to remove portions of the insulating layer 150 and the support bar insulating film 152 corresponding to the contacts 142 to form recesses. 154 is formed (step 11). As a result, the contact 142 is exposed at the bottom of the recess 154. As described above, the recesses 154 are provided so as to correspond to the respective contacts 142, so that a plurality of the recesses 154 are provided on the surface of the wafer W. The height of the recess 154 is about 2 to 3 μm, and its aspect ratio is about 20 to 30, which is a very elongated recess.

Next, as shown in FIG. 26C, a first thin film 156 made of a TiN film is formed with a predetermined thickness on the entire surface of the insulating layer including the surface in the recess 154 (step 12). ). When the first thin film 156 is formed, a high-quality TiN film having a low specific resistance and a low resistivity is formed by using the film forming method described above. Here, the first thin film 156 made of a TiN film and the contact 142 are electrically connected.

Next, by performing, for example, CMP (Chemical Mechanical Polishing) polishing on the wafer W on which the first thin film 156 is formed in this way, as shown in FIG. The first thin film 156 formed on the upper surface is removed, thereby leaving the first thin film 156 formed on the surface in the recess 154 (step 13).

Next, only the insulating layer 150 is removed by performing an etching process using, for example, hydrofluoric acid (step 14). As a result, as shown in FIG. 26E, the remaining first thin film 156 remains as a cylindrical projection to form a lower electrode 158 around the support bar insulation. The film 152 remains as a support bar 160 in a joined state. A plan view of FIG. 26E is shown in FIG. 27. Support bars 160 extend around the lower electrode 158 in four directions, and the lower electrodes 158 adjacent in the vertical and horizontal directions are connected to each other by the support bars 160. To support each other.

Next, as shown in FIG. 26F, a high dielectric constant film 162 is formed with a predetermined thickness on the entire surface of the wafer W including the inner and outer surfaces of the lower electrode 158 which is a cylindrical projection. (Step 15). For the high dielectric constant film 162, a material having a relative dielectric constant of, for example, 10 or more is used. As this material, for example, HfO ₂ , HfZrO, ZrO ₂ or the like can be used.

When the high dielectric constant film 162 is thus formed, the second thin film 164 made of a TiN film is formed with a predetermined thickness on the entire surface of the wafer W including the inner and outer surfaces of the high dielectric constant film 162. (Step 16). When the second thin film 124 is formed, a high-quality TiN film having a low specific resistance and a low resistivity is formed by using the film forming method described above.

Next, by performing an etching process, the second thin film 164 and the high dielectric constant film 162 other than the portion corresponding to the lower electrode 158 which is a cylindrical protrusion are removed, as shown in FIG. As described above, the remaining portion of the second thin film 164 becomes the upper electrode 166, and a large number of capacitors 168 including the lower electrode 158, the high dielectric constant film 162, and the upper electrode 166 are formed in a state of being separated from each other. (Step 17).

Next, an example of an element structure when such a capacitor is applied to a capacitor in a DRAM memory cell will be described. FIG. 28 is a sectional view showing such an element structure. In FIG. 28, the support bar is omitted. As shown in FIG. 28, a gate electrode 184 is formed through a gate insulating film 182 in a region partitioned by a field oxide film 180 on a semiconductor substrate 170 made of, for example, a silicon substrate. Impurity regions (source / drain regions) 186 are formed on the main surface of the semiconductor substrate 170 on both sides of the gate electrode 184 by ion implantation using the gate electrode 184 as a mask. On the gate electrode 184, an interlayer insulating film 188 is formed over the entire main surface of the semiconductor wafer W, and a contact plug 190 for connecting to one of the source / drain regions 156 is formed at a predetermined position of the interlayer insulating film 188. ing.

A bit line 192 is connected to the contact plug 190. An interlayer insulating film 194 is formed on the interlayer insulating film 188 including the bit line 192, and a contact plug 142 for connecting to the other of the source / drain regions 156 is formed through the interlayer insulating films 188 and 184. Yes. Then, the above-described cylindrical or cylindrical capacitor 168 is formed on the contact plug 142.

In such a capacitor 168, the lower electrode 158 and the upper electrode 166 are both formed of a TiN film with reduced stress, and as a result, warpage of the wafer W itself can be prevented. In addition, the capacitor 168 itself can be prevented from cracking or cracking. Note that the support bar is not essential in the capacitor.

<Other applications of the present invention>
In the above-described embodiment, an example in which the present invention is applied to the formation of a TiN film and a W film has been described. However, the present invention is not limited to this, and Ti, W, Ta, Ni, Hf, Zr, The present invention can also be applied to refractory metal films such as Ru, nitride films thereof, and compound films of these substances.

In the above embodiment, the TiN film is described as an example of being used for an electrode having a capacitor structure. However, the present invention is not limited to this, and can be applied to wirings such as the contacts 142 and 190 and the bit line 192 in FIG. It can also be applied to further upper layer contacts, global wiring, etc. that are not performed.

Further, in the above embodiment, the capacitive coupling type using high frequency power generated from the high frequency power source 98 is shown as the plasma generating means, but the present invention is not limited to this, and it is generated by using a microwave generation source. A method of introducing a microwave into a processing vessel through a microwave antenna to form plasma, or an inductive coupling type may be used.

In addition, although a semiconductor wafer is described as an example of the object to be processed here, this semiconductor wafer includes a compound semiconductor substrate such as GaAs, SiC, or GaN in addition to a silicon substrate. Further, the present invention is not limited to a semiconductor wafer, and the present invention can be applied to a glass substrate, a ceramic substrate, or the like used for a liquid crystal display device.

Claims (21)

Supplying a raw material gas containing titanium and a nitrogen-containing gas to a substrate to be processed in a processing container to form a titanium nitride film on the substrate to be processed by heat treatment;
And a treatment for reducing the stress of the film caused by plasma on the titanium nitride film. The titanium nitride film is formed by a first step of supplying the source gas and the nitriding gas to the substrate to be processed simultaneously, and a second step of stopping the supply of the source gas and supplying the nitriding gas to the substrate to be processed. The film forming method according to claim 1, wherein the film forming method is performed by alternately repeating. 2. The film forming method according to claim 1, wherein the titanium nitride film is formed by alternately repeating the supply of the source gas and the supply of the nitriding gas. The film forming method according to claim 3, wherein the inside of the processing container is purged between the first step and the second step. The film forming method according to claim 1, wherein a temperature at the time of forming the titanium nitride film is set in a range of 250 to 1000 ° C. The film forming method according to claim 1, wherein the source gas is TiCl ₄ gas and the nitrogen-containing gas is NH ₃ gas. 2. The film forming method according to claim 1, wherein a temperature at the time of the processing for reducing the stress of the film caused by the plasma is set in a range of 250 to 1000 ° C. 2. The process according to claim 1, wherein the treatment for reducing the stress of the film by the plasma uses at least one selected from the group consisting of N ₂ gas, H ₂ gas, NH ₃ gas, and rare gas as a plasma generation gas. Membrane method. The film forming method according to claim 1, wherein the formation of the titanium nitride film and the processing for reducing the stress of the film due to the plasma are performed in the same processing container. The film forming method according to claim 9, wherein the source gas is TiCl ₄ gas, the nitrogen-containing gas is NH ₃ gas, and the plasma generation gas is NH ₃ gas. The film forming method according to claim 1, wherein the stress of the film is controlled by adjusting a temperature and / or a time during the process of reducing the stress of the film due to the plasma. 2. The film forming method according to claim 1, wherein the titanium nitride film constitutes an electrode of a capacitor and is formed in a recess formed on a surface of the substrate to be processed. One electrode of the capacitor formed in a cylindrical shape is formed on the surface of the substrate to be processed, and the titanium nitride film is formed as the other electrode through a dielectric film thereon. The film-forming method of Claim 12. A first step of supplying a raw material gas containing titanium and a nitrogen-containing gas to a substrate to be processed in a processing container and forming a titanium nitride film on the substrate to be processed by heat treatment;
The supply of the source gas is stopped and the nitrogen-containing gas is supplied to nitride the titanium nitride film, and at the same time, the second step of generating plasma in the processing vessel to reduce the stress of the film is alternately repeated. Film forming method. The film forming method according to claim 14, wherein the inside of the processing container is purged between the first step and the second step. The film forming method according to claim 14, wherein the temperatures of the first step and the second step are set within a range of 250 to 1000 ° C. The film forming method according to claim 14, wherein the source gas is TiCl ₄ gas and the nitrogen-containing gas is NH ₃ gas. The film forming method according to claim 17, wherein the plasma generating gas is NH ₃ . The film forming method according to claim 14, wherein the stress of the film is controlled by adjusting the time and / or the number of cycles of the second step. Supplying a source gas containing tungsten and a reducing gas to the substrate to be processed in the processing container to form a tungsten film on the substrate to be processed by heat treatment;
And performing a treatment for reducing the stress of the film caused by plasma on the tungsten film. A capacitor forming method for forming a capacitor on a surface of a substrate to be processed,
Forming a plurality of recesses on the surface of the insulating layer provided on the surface of the substrate to be processed;
A titanium nitride film is formed on the substrate by heat treatment by supplying a source gas containing nitrogen and a nitrogen-containing gas to the substrate to be processed in the processing vessel on the surface of the insulating layer including the surfaces in the plurality of recesses. Forming a first thin film made of a titanium nitride film using a film forming method including forming and applying a treatment to reduce the film stress caused by plasma to the titanium nitride film;
Removing the first thin film on the surface of the insulating layer to leave the first thin film on the surface in the plurality of recesses;
Leaving the first thin film as a cylindrical protrusion by removing the insulating layer;
Forming a high dielectric constant film on the entire surface including the surface of the remaining cylindrical projection;
Supplying a titanium-containing source gas and a nitrogen-containing gas to a substrate to be processed in a processing container on the surface of the high dielectric constant film to form a titanium nitride film on the substrate to be processed by heat treatment; Forming a second thin film made of a titanium nitride film by using a film forming method having a process for reducing the stress of the film caused by plasma on the titanium film;
Etching away the second thin film remaining between the plurality of cylindrical protrusions and the high dielectric constant film to form a plurality of electrically separated capacitors;
A method of forming a capacitor.

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