JP2004228324A - Method of forming silicide film, forming device therefor and method of controlling film thickness - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a silicide film capable of uniformly forming the thickness of a cobalt silicide film. <P>SOLUTION: The method of forming the silicide film includes the steps for forming an interdiffused layer in which a high melting point metal film is formed on a silicon substrate, and the interdiffused layer of a high melting point metal constituting the high melting point metal film and silicon constituting the silicon substrate is formed on an interface between the high melting point metal film and the silicon substrate; and heating for forming an interdiffusion preventing layer for preventing the further interdiffusion of the high melting point metal and the silicon on the interface between the high melting point metal film and the interdiffused layer, to heat the silicon substrate with the high melting point metal film and the interdiffused layer formed thereon in the atmosphere containing nitrogen element. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of forming a silicide film for reducing the resistance of a gate and source / drain impurity diffusion regions of a transistor formed on a silicon substrate, a device for forming the silicide film, and a method of controlling the film thickness.
[0002]
[Prior art]
In a MOS transistor composed of a gate region formed of polysilicon and a source / drain region formed by diffusing impurities into a silicon substrate, a voltage applied to the gate region changes the source region to the drain region. The flowing current is controlled. Here, since the resistance in the gate region or the source region / drain region affects the delay of the transistor operation, it is indispensable to reduce the resistance of the gate region and the source region / drain region in order to increase the speed of the MOS transistor. is there.
[0003]
Therefore, conventionally, as shown in Non-Patent Document 1, as a means for lowering the resistance of a gate region and a source region / drain region, a salicide (a self-aligned reaction between a refractory metal and silicon) is used. A Self Aligned Silicide (Self Aligned Silicide) process is used.
[0004]
Hereinafter, a conventional salicide process for lowering the resistance of the gate and source / drain impurity diffusion regions of a transistor formed on a silicon substrate will be described with reference to the drawings. FIGS. 8A to 8D are cross-sectional views illustrating a conventional method for forming a silicide film.
[0005]
Referring to FIG. 8A, a gate insulating film 82 serving as a gate region of a MOS transistor and a polysilicon electrode 99 are formed on a silicon substrate separated by a field oxide film 81.
[0006]
Side walls 83 are formed on both sides of the gate insulating film 82 and the polysilicon electrode 99. On the silicon substrate on both sides of the sidewall 83, an impurity diffusion layer 90 serving as a source region or a drain region is formed.
[0007]
In such a structure, clean silicon must be exposed on the outermost surface of the region that requires low resistance, and all the regions that do not require low resistance are formed by a silicon oxide film or silicon nitride film. Must be covered.
[0008]
Next, referring to FIG. 8B, a cobalt deposition film 94 is deposited so as to cover the polysilicon electrode 99, the sidewalls 83, the impurity diffusion layers 90, and the field oxide films 81. Then, a protective film 91 made of TiN or the like is deposited so as to cover the cobalt deposited film 94.
[0009]
The interface between the deposited cobalt film 94 and the polysilicon electrode 99 and the interface between the deposited cobalt film 94 and the impurity diffusion layer 90 are provided between the cobalt and silicon mutual diffusion layer 2. Is formed to a thickness of about 2 nanometers (nm) to 3 nanometers.
[0010]
Then, referring to FIG. 8C, when a heat treatment of 400 ° C. or more is performed in a nitrogen atmosphere from this state, the interdiffusion layer 2 of cobalt and silicon is transformed into a cobalt silicide film 93 and the cobalt vapor deposition film 94 The diffusion of cobalt atoms into the cobalt silicide film 93 continues, and the cobalt silicide film 93 grows.
[0011]
Next, referring to FIG. 8D, the growth of the cobalt silicide film 93 as described above consumes the cobalt deposition film 94 immediately above or continues until the heat treatment is completed. The final cobalt film thickness must be adjusted based on the thickness and the heat treatment conditions. Thereafter, only the protective film 91 and the cobalt vapor deposited film 94 are removed by cleaning having a selectivity to the silicon oxide film such as sulfuric acid / hydrogen peroxide solution, and if necessary, the cobalt silicide film 93 is made to have the lowest resistance. The additional heat treatment is performed in a nitrogen atmosphere.
[0012]
As shown in FIG. 8D, the semiconductor device processed in this manner is made of cobalt silicide that has been selectively reduced in resistance only in a portion where clean silicon was exposed in the state shown in FIG. 8A. A film 93 is formed.
[0013]
[Patent Document 1]
JP-A-10-223560
[0014]
[Non-patent document 1]
Koyu Tango and Junichi Nishizawa, "Semiconductor Engineering Series 9 Semiconductor Process Technology", P36, published by Baifukan
[0015]
[Problems to be solved by the invention]
However, in the above-described conventional configuration, since the thickness of the cobalt silicide film 93 is determined based on the thickness of the cobalt vapor deposition film 94 deposited on the silicon surface before the heat treatment, the thickness of the cobalt vapor deposition film 94 may vary. If this occurs, for example, in the case of a pattern in which the distance between the gate electrodes is small and surrounds the silicon substrate, the resistance varies because the thickness of the cobalt silicide film 93 after the heat treatment is not uniform. Had a problem.
[0016]
If the thickness of the cobalt silicide film 93 is too large, a current leaks from the boundary of the diffusion layer to the silicon substrate. For this reason, there is a possibility that the transistor performance is deteriorated. As described above, when the thickness of the cobalt silicide film 93 varies, there is a problem that the uniformity of transistor performance is also impaired.
[0017]
SUMMARY OF THE INVENTION An object of the present invention is to provide a method of forming a silicide film capable of forming a uniform thickness of a cobalt silicide film, an apparatus for forming the silicide film, and a method of controlling the film thickness.
[0018]
[Means for Solving the Problems]
In the method for forming a silicide film according to the present invention, a refractory metal film is formed on a silicon substrate, and an interdiffusion layer of a refractory metal forming the refractory metal film and silicon forming the silicon substrate is formed by the high melting point metal. Forming an interdiffusion layer at the interface between the melting point metal film and the silicon substrate; and forming the interdiffusion prevention layer for preventing further interdiffusion between the high melting point metal and the silicon with the high melting point metal film. A heat treatment step of heat-treating the silicon substrate on which the refractory metal film and the interdiffusion layer are formed in an atmosphere containing a nitrogen element in order to form the silicon substrate at the interface between the interdiffusion layers. It is characterized.
[0019]
An apparatus for forming a silicide film according to the present invention forms a refractory metal film on a silicon substrate, and forms an interdiffusion layer between a refractory metal constituting the refractory metal film and silicon constituting the silicon substrate. An interdiffusion layer forming chamber for forming an interface between the melting point metal film and the silicon substrate; and an interdiffusion preventing layer for preventing further interdiffusion between the high melting point metal and the silicon. In order to form at the interface between the film and the interdiffusion layer, the silicon substrate on which the refractory metal film and the interdiffusion layer were formed was provided for heat treatment in an atmosphere containing a nitrogen element. A first heat treatment chamber; and a second heat treatment chamber for performing heat treatment such that the interdiffusion layer heat-treated in the first heat treatment chamber is transformed into a silicide film. And it features.
[0020]
The silicide film thickness control method according to the present invention includes a first step of forming a refractory metal film having a substantially uniform thickness on a semiconductor substrate to form an initial mutual diffusion layer of refractory metal and silicon; A second step of heating the semiconductor substrate to a predetermined temperature while raising the temperature of the semiconductor substrate to a predetermined temperature under an atmosphere containing ammonia by delaying by a plurality of set time conditions from the start of the heating, and performing a heat treatment for a predetermined time; A third step of obtaining a film thickness of a final interdiffusion layer of a high melting point metal and silicon for each combination of a temperature raising rate condition and a plurality of set time conditions.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
In the method for forming a silicide film according to the present embodiment, an interdiffusion preventing layer for preventing further interdiffusion between a refractory metal and silicon is formed at an interface between the refractory metal film and the interdiffusion layer. For this purpose, a heat treatment step is performed in which the silicon substrate on which the refractory metal film and the interdiffusion layer are formed is heat-treated in an atmosphere containing a nitrogen element. Therefore, the mutual diffusion preventing layer formed at the interface between the high melting point metal film and the interdiffusion layer prevents further mutual diffusion between the high melting point metal and silicon. Therefore, the thickness of the cobalt silicide film transformed from the interdiffusion layer becomes uniform. As a result, variations in the resistance of the gate region, the source region, and the drain region can be suppressed.
[0022]
Preferably, the interdiffusion layer that has been heat-treated in the heat-treating step is transformed into a silicide film.
[0023]
The silicon substrate has a gate electrode formed in a gate region, and an impurity diffusion layer formed in each of a source region and a drain region. The inter-diffusion layer forming step includes the step of forming the gate electrode and the impurity Preferably, the refractory metal film is formed so as to cover the diffusion layer.
[0024]
In the step of forming an interdiffusion layer, the interdiffusion layer is preferably formed at an interface between the gate electrode and the refractory metal film and at an interface between the impurity diffusion layer and the refractory metal film.
[0025]
Preferably, the gate electrode is constituted by a polysilicon electrode.
[0026]
In the heat treatment step, the mutual diffusion preventing layer is preferably formed to have a thickness of 1 nanometer or more.
[0027]
It is preferable that the method further includes a removing step of removing the refractory metal film after the heat treatment step.
[0028]
It is preferable that the method further includes, after the removing step, an additional heat treatment step of performing an additional heat treatment on the silicide film in an atmosphere containing a nitrogen element in order to lower the resistance of the silicide film.
[0029]
The atmosphere containing the nitrogen element is preferably a nitrogen or argon atmosphere to which ammonia has been added.
[0030]
It is preferable that the interdiffusion preventing layer contains silicon nitride.
[0031]
The atmosphere containing the nitrogen element is preferably a nitrogen or argon atmosphere to which ammonia and oxygen are added.
[0032]
It is preferable that the mutual diffusion preventing layer contains silicon oxynitride.
[0033]
The refractory metal is a metal that does not form a nitrogen compound on its surface when heat-treated at 400 ° C. or more, and the refractory metal film is a film that diffuses nitrogen to the lower surface of the refractory metal film. Is preferred.
[0034]
Preferably, the high melting point metal is cobalt.
[0035]
It is preferable that the high melting point metal film is formed at a substrate temperature of 100 ° C. or more and a thickness of 5 nanometers or more.
[0036]
It is preferable that the interdiffusion layer is formed to have a thickness of not less than 2 nanometers and not more than 3 nanometers.
[0037]
The heat treatment is preferably performed at a temperature of 400 ° C. or higher.
[0038]
In the silicide film forming apparatus according to the present embodiment, a mutual diffusion preventing layer for preventing further mutual diffusion between the high melting point metal and silicon is formed at the interface between the high melting point metal film and the mutual diffusion layer. To this end, a first heat treatment chamber is provided for heat-treating the silicon substrate on which the refractory metal film and the interdiffusion layer are formed in an atmosphere containing a nitrogen element. Therefore, the mutual diffusion preventing layer formed at the interface between the high melting point metal film and the interdiffusion layer prevents further mutual diffusion between the high melting point metal and silicon. Therefore, the thickness of the cobalt silicide film transformed from the interdiffusion layer becomes uniform. As a result, variations in the resistance of the gate region, the source region, and the drain region can be suppressed.
[0039]
The apparatus further includes a first load chamber provided to transfer the silicon substrate on which the refractory metal film and the interdiffusion layer are formed by the interdiffusion layer forming chamber to the first heat treatment chamber in a vacuum state. Is preferred.
[0040]
The apparatus may further include a second load chamber provided to transfer the silicon substrate on which the mutual diffusion preventing layer is formed by the first heat treatment chamber to the second heat treatment chamber in a vacuum state.
[0041]
The first heat treatment chamber is preferably connected to an ammonia gas introduction unit provided for introducing ammonia gas into the atmosphere containing the nitrogen element.
[0042]
It is preferable that oxygen introducing means provided for introducing oxygen into the atmosphere containing the nitrogen element is further connected to the first heat treatment chamber.
[0043]
Preferably, the refractory metal film is cobalt, and the interdiffusion layer forming chamber forms the cobalt on the silicon substrate by sputtering.
[0044]
In the silicide film thickness control method according to the present embodiment, the third step of obtaining the film thickness of the final mutual diffusion layer of refractory metal and silicon for each combination of a plurality of temperature raising rate conditions and a plurality of set time conditions is provided. Is provided. For this reason, a calibration curve can be created for each heating rate with the thickness of the initial interdiffusion layer as the origin, and a silicide film having a desired film thickness can be formed.
[0045]
The refractory metal film is preferably made of cobalt.
[0046]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0047]
(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of a semiconductor device in which a mutual diffusion preventing layer 1 is formed in the method for manufacturing a semiconductor device according to the first embodiment. On a silicon substrate 5 separated by a field oxide film 21, a gate insulating film 22 and a polysilicon electrode 9 which are to be gate regions of a MOS transistor are formed in this order.
[0048]
On the polysilicon electrode 9, the cobalt silicide film 3 is formed. On the cobalt silicide film 3, the mutual diffusion preventing layer 1 is formed. Side walls 23 are formed on both side surfaces of the cobalt silicide film 3, the polysilicon electrode 9, and the gate insulating film 22.
[0049]
On the silicon substrate 5 on both sides of the sidewall 23, an impurity diffusion layer 10 serving as a source region or a drain region is formed. On the impurity diffusion layer 10, a cobalt silicide film 3 is formed. On the cobalt silicide film 3, an interdiffusion preventing layer 1 is formed.
[0050]
Refractory metal film 4 is formed so as to cover mutual diffusion preventing layer 1, side wall 23 and field oxide film 21. The high melting point metal film 4 is formed of a cobalt vapor deposition film.
[0051]
In this manner, the thin interdiffusion preventing layer 1 is formed between the high melting point metal film 4 and the cobalt silicide film 3 so as to limit the mutual diffusion of atoms from the high melting point metal film 4 and the cobalt silicide film 3. ing.
[0052]
Hereinafter, a method of manufacturing a semiconductor device for forming such a mutual diffusion preventing layer 1 will be described. 2A to 2D are cross-sectional views for explaining a method for forming a silicide film according to the first embodiment.
[0053]
Referring to FIG. 2A, a gate insulating film 22 serving as a gate region of a MOS transistor and a polysilicon electrode 9 are formed on a silicon substrate 5 separated by a field oxide film 21.
[0054]
Side walls 23 are formed on both side surfaces of the gate insulating film 22 and the polysilicon electrode 9. On the silicon substrate 5 on both sides of the sidewall 23, an impurity diffusion layer 10 serving as a source region or a drain region is formed.
[0055]
In such a structure, clean silicon must be exposed on the outermost surface of the region that requires low resistance, and all the regions that do not require low resistance are formed by a silicon oxide film or silicon nitride film. Must be covered.
[0056]
Next, referring to FIG. 2B, the refractory metal film 4 is formed to a thickness of approximately 5 (Nm) or more. The high melting point metal film 4 is formed of a cobalt vapor deposition film.
[0057]
The interface between the high-melting point metal film 4 and the polysilicon electrode 9 and the interface between the high-melting point metal film 4 and the impurity diffusion layer 10 are interdiffused between cobalt and silicon. Layer 2 is formed to a thickness of about 2 nanometers (nm) to 3 nanometers.
[0058]
Referring to FIG. 2C, in this state, a heat treatment of 400 ° C. or more is performed in an ammonia atmosphere or an atmosphere of nitrogen dilution of 0.5 or more in nitrogen. Then, the interdiffusion layer 2 of cobalt and silicon is transformed into a cobalt silicide film 3. At the same time, an amorphous silicon nitride layer is formed between the refractory metal film 4 and the cobalt silicide film 3. This becomes the mutual diffusion preventing layer 1 for preventing the mutual diffusion of silicon and cobalt atoms.
[0059]
When the mutual diffusion preventing layer 1 is formed to a thickness of 1 nm or more, mutual diffusion between cobalt and silicon is prevented. Therefore, since the atoms of the cobalt silicide film 3 and the refractory metal film 4 composed of the cobalt vapor deposition film are not supplied to each other, the reaction by the heat treatment does not proceed.
[0060]
Thereafter, the refractory metal film 4 and the interdiffusion prevention layer 1 are removed by cleaning such as sulfuric acid / hydrogen peroxide with a selectivity to the silicon oxide film. Then, if necessary, an additional heat treatment is performed in a nitrogen atmosphere to minimize the resistance of the cobalt silicide film 3.
[0061]
As shown in FIG. 2D, the semiconductor device treated in this manner is a cobalt silicide film 3 selectively reduced in resistance only in a portion where clean silicon is exposed in the state shown in FIG. Is formed.
[0062]
By forming an interlayer insulating film mainly composed of a silicon oxide film on this semiconductor device and arranging wirings and contacts, the MOS transistor operates faster than a transistor that does not use a low-resistance cobalt silicide film. Can be done.
[0063]
As described above, in order to reduce the resistance of the source / drain region and the gate region of the semiconductor device, etc., after depositing the high melting point metal film 4 composed of a cobalt vapor deposited film on the semiconductor device having a clean silicon surface, By performing a heat treatment in an ammonia atmosphere or a nitrogen atmosphere containing ammonia, an interdiffusion preventing layer 1 is formed between the refractory metal film 4 and the cobalt silicide layer 3. By controlling, a uniform cobalt silicide film 3 with a small thickness variation can be manufactured.
[0064]
In the above embodiment, the high melting point metal film 4 composed of a cobalt vapor deposition film is deposited, and the low resistance cobalt silicide film 3 is formed. However, the present invention is not limited to this. The metal element constituting the high-melting metal film 4 is a metal element capable of forming the mutual diffusion preventing layer 1 at an initial stage of the silicidation reaction by diffusion of nitrogen atoms due to ammonia during the heat treatment. In addition, any resistance may be used as long as the resistance is low.
[0065]
As described above, according to the first embodiment, the interdiffusion preventing layer 1 for preventing further interdiffusion between the refractory metal 4 and silicon is provided at the interface between the refractory metal film 4 and the interdiffusion layer 2. In order to form, a heat treatment step is performed in which the silicon substrate 5 on which the refractory metal film 4 and the interdiffusion layer 2 are formed is heat-treated in an atmosphere containing a nitrogen element. Therefore, the mutual diffusion preventing layer 1 formed at the interface between the high melting point metal film 4 and the cobalt silicide film 3 prevents further mutual diffusion between the high melting point metal 4 and silicon. Therefore, the thickness of the cobalt silicide film 3 transformed from the interdiffusion layer 2 becomes uniform. As a result, variations in the resistance of the gate region, the source region, and the drain region can be suppressed.
[0066]
(Embodiment 2)
FIG. 3 is a plan sectional view showing a configuration of the silicide film forming apparatus 150 according to the second embodiment. The silicide film forming apparatus 150 is a single-wafer-type apparatus that performs the method of forming a silicide film described in the first embodiment.
[0067]
The silicide film forming apparatus 150 includes the interdiffusion layer forming chamber 11. The interdiffusion layer forming chamber 11 forms a refractory metal film on a silicon substrate, and forms an interdiffusion layer of a refractory metal forming the refractory metal film and silicon forming the silicon substrate on the refractory metal film and the silicon substrate. Is provided at the interface between the substrate and the substrate.
[0068]
The silicide film forming apparatus 150 is provided with a heat treatment chamber 12. The heat treatment chamber 12 is provided at the interface between the refractory metal film and the interdiffusion layer to form an interdiffusion preventing layer for preventing further interdiffusion between the refractory metal and silicon. It is provided to heat-treat the silicon substrate on which the diffusion layer is formed in an atmosphere containing a nitrogen element.
[0069]
The heat treatment chamber 12 has an ammonia gas introducer 16 provided for introducing ammonia gas into an atmosphere containing a nitrogen element, and an oxygen introducer 17 provided for introducing oxygen into an atmosphere containing a nitrogen element. And are connected.
[0070]
A load chamber 14 is provided between the interdiffusion layer forming chamber 11 and the heat treatment chamber 12. The load chamber 14 is provided for transferring the silicon substrate on which the refractory metal film and the interdiffusion layer are formed by the interdiffusion layer forming chamber 11 to the heat treatment chamber 12 in a vacuum state.
[0071]
The silicide film forming apparatus 150 includes a heat treatment chamber 13. The heat treatment chamber 13 performs heat treatment so that the interdiffusion layer heat-treated in the heat treatment chamber 12 is transformed into a silicide film.
[0072]
A load chamber 15 is provided between the heat treatment chamber 12 and the heat treatment chamber 13. The load chamber 15 is provided for transferring the silicon substrate on which the mutual diffusion preventing layer is formed by the heat treatment chamber 12 to the heat treatment chamber 13 in a vacuum state.
[0073]
In the silicide film forming apparatus 150, a main load chamber 24 is provided so as to be able to communicate with the mutual diffusion layer forming chamber 11 and the heat treatment chamber 13. A cassette station 25 is connected to the main load chamber 24.
[0074]
The operation of the silicide film forming apparatus 150 thus configured will be described. First, a silicon wafer for which MOS transistors have been manufactured to the structure shown in FIG. 2A in the first embodiment is set in the cassette station 25, evacuated, and then moved to the main load chamber 24.
[0075]
Next, the wafers are moved one by one to the interdiffusion layer forming chamber 11, and the cobalt deposition film 4 is sputter deposited at a substrate temperature of 100 ° C. or higher. Thereafter, the substrate is moved to a heat treatment chamber 12 for forming a mutual diffusion preventing layer through a load chamber 14 in a vacuum.
[0076]
Then, in the heat treatment chamber 12, the inside of the chamber is decompressed to near atmospheric pressure by nitrogen, and then heat treatment is performed by heating with a halogen lamp. Ammonia gas is introduced from the ammonia gas introducer 16 and heated at a temperature of 450 ° C. or less so as to form a nitrogen atmosphere containing After the completion of the heat treatment, the chamber is evacuated to 0.1 mPa or less, and then moved to the heat treatment chamber 13 through the load chamber 15.
[0077]
In the heat treatment chamber 13, the halogen lamp is heated again at 450 ° C. to 500 ° C. for about 20 seconds in a nitrogen atmosphere, evacuated and then returned to the main load chamber 24, and the wafer is taken out from the cassette station 25 to remove the cobalt silicide layer. 3 can be formed with good reproducibility.
[0078]
Such processing can be performed by providing independent vacuum load chambers 14 and 15 between the interdiffusion layer forming chamber 11 and the heat treatment chamber 13, and providing an interdiffusion prevention layer between the load chambers 14 and 15. This is because a heat treatment chamber 12 for forming the heat treatment is provided.
[0079]
After the deposition of the cobalt vapor-deposited film 4 and before the process for forming the mutual diffusion preventing layer 1, the possibility that extra impurities are mixed into the cobalt vapor-deposited film 4 is eliminated, and the mutual diffusion is prevented. By diffusing impurities only in the heat treatment chamber 12 for forming the layer 1, the mutual diffusion preventing layer 1 can be formed with high accuracy.
[0080]
Further, by providing a vacuum load chamber 15 between the heat treatment chamber 12 and the heat treatment chamber 13 for forming the interdiffusion prevention layer 1, the entry of impurities into other chambers in the apparatus can be prevented. Thus, the mutual diffusion preventing layer 1 can be formed stably. Further, an etching processing chamber by Ar sputtering may be added as needed to keep the silicon surface clean.
[0081]
In the second embodiment, the example of the single-wafer method has been described. However, in consideration of the deposition conditions and the heat treatment conditions of the cobalt vapor deposition film, even if a processing apparatus of the badge method is used, mutual diffusion can be prevented by the same method. A silicide film using a layer can be formed.
[0082]
In the second embodiment, cobalt is used as a material for forming the silicide film. However, nitrogen atoms are diffused by ammonia into the deposited film from above the deposited film during the heat treatment, and interdiffusion occurs at an initial stage of the silicide reaction. If the silicide is a stable and low-resistance material which is a metal atom capable of forming a prevention layer, a silicide layer having a mutual diffusion prevention layer can be formed by a similar silicide forming apparatus.
[0083]
As described above, according to the silicide forming apparatus according to the second embodiment, since the formation of the interdiffusion preventing layer between the cobalt deposition film and the cobalt silicide film can be controlled, a silicide having a desired film thickness is formed. be able to.
[0084]
(Embodiment 3)
FIG. 4 is a flowchart showing a procedure for determining an initial silicide film thickness according to the third embodiment. Since the thickness of the interdiffusion layer of cobalt and silicon varies depending on the conditions for depositing the cobalt vapor deposition film, the thickness of the cobalt silicide film formed based on this varies. For this reason, it is necessary to determine the thickness of the initial cobalt silicide film based on the flowchart shown in FIG.
[0085]
FIG. 5 is a graph for explaining the relationship between the ammonia introduction time and the temperature increase rate according to the third embodiment. In FIG. 5, the surface temperature of the silicon substrate in the chamber where the heat treatment is performed in the nitrogen atmosphere to which ammonia is added is plotted with the heat treatment time on the horizontal axis and the heat treatment temperature on the vertical axis.
[0086]
At 0 second as the heat treatment start time, introduction of ammonia into the chamber is started. The heat treatment start time is 0 second, which is the ammonia introduction start time. The slope of the straight line shown in FIG. 5 indicates the rate of temperature increase by the heat treatment. The time when the heat treatment temperature reaches 400 ± 50 degrees indicates the introduction limit time.
[0087]
Referring to FIG. 4, in order to determine the initial cobalt silicide film thickness, first, the deposition conditions for the refractory metal film 4 composed of a cobalt vapor deposition film are determined (step S1). Specifically, a natural oxide film or the like on the surface of the wafer is removed by cleaning, and a cobalt vapor-deposited film is formed on a wafer on which a pattern exposing clean silicon is not formed. Then, for example, the film thickness is measured by a fluorescent X-ray apparatus or the like, the crystal orientation is measured by an X-ray diffractometer or the like, the impurity amount in the film is measured by a secondary ion mass spectrometer or the like, and the wafer surface and Determining deposition conditions with excellent uniformity between wafers.
[0088]
Next, the thickness of the cobalt-silicon interdiffusion layer 2 in the cobalt deposition film formed according to the determined deposition conditions is measured by a transmission electron microscope or the like (Step S2), and is constant within the wafer surface and between wafers. Is confirmed (step S3). If it is not constant (NO in step S3), the deposition conditions of the cobalt vapor deposition film, such as the substrate temperature setting when depositing the cobalt vapor deposition film, are reviewed (step S4). Then, the process returns to step S1.
[0089]
After the thickness of the interdiffusion layer between cobalt and silicon is made constant (YES in step S3), ammonia is introduced simultaneously with the start of the heat treatment (step S5). Then, through a selective etching step using a mixed solution of sulfuric acid and hydrogen peroxide (step S6), a high-temperature heat treatment of 750 ° C. or more is performed in a nitrogen atmosphere (step S7), and a cobalt silicide film 3 is formed. The film thickness of No. 3 is measured (step S8).
[0090]
Next, it is determined whether or not the thickness of the cobalt silicide film 3 has reproducibility within the wafer surface, between wafers, and between lots (step S9). If the thickness of the cobalt silicide film is not reproducible within the wafer surface, between wafers, or between lots (NO in step S9), the amount of ammonia introduced into the heat treatment chamber, the timing of introduction, the temperature rise rate, and the cobalt silicide in the selective etching step The thinning of the film and the like are reviewed again (S10). Then, the process returns to step S5.
[0091]
If the cobalt silicide film thickness has reproducibility within the wafer surface, between wafers, and between lots (YES in step S9), the process is terminated by setting the film thickness at this time to the initial cobalt silicide film thickness 20 (step S10). .
[0092]
FIG. 6 is a flowchart showing a procedure for determining a silicide film thickness according to the third embodiment.
[0093]
Based on the deposition conditions of the cobalt vapor deposition film determined by the method described above with reference to FIGS. 4 and 5, a cobalt vapor deposition film is deposited (step S11). Then, an interdiffusion layer 2 of cobalt and silicon is formed, and processing is performed for each wafer under the same temperature raising rate and three or more types of conditions in which the ammonia introduction time is 0.1 second or more (step S12). Next, each wafer is selectively etched under the same conditions as in FIG. 5 (Step S13), and is subjected to a high-temperature heat treatment at 750 ° C. or higher (Step S14), and the thickness of the formed cobalt silicide film 3 is measured (Step S14). S15).
[0094]
FIG. 7 is a graph for explaining a calibration curve for each temperature rise rate of the silicide film thickness according to the third embodiment. The horizontal axis indicates the ammonia introduction time, and the vertical axis indicates the thickness of the cobalt silicide film 3.
[0095]
The thickness of the cobalt silicide film 3 measured in step S15 is, as shown in FIG. 7, a calibration curve 22 indicated by a straight line rising to the right passing through the initial cobalt silicide film thickness 20 determined by the flowchart shown in FIG. (Step S16). At this time, if the straight line becomes a straight line or a curve that does not include the initial cobalt silicide film thickness 20, there is a variation in the cobalt silicide formation process, and the initial cobalt silicide film thickness is determined again based on the flowchart of FIG. I do.
[0096]
The time when the thickness of the cobalt silicide film is not proportional to the increase of the ammonia introduction time indicates that the cobalt vapor deposition film has been completely consumed. The temperature rate is reduced (step S18), the same processing is performed based on the flowchart of FIG. 6, and a new cobalt silicide film thickness is plotted. In this way, a calibration curve 22 for each heating rate as shown in FIG. 7 is created. The calibration curve 22 for each rate of temperature increase makes it possible to select the conditions under which the cobalt silicide film thickness required for semiconductor device fabrication can be formed most stably, with good reproducibility, and with high throughput.
[0097]
The thickness of the cobalt silicide film 3 using the interdiffusion preventing layer 1 can be controlled because the cobalt and silicon forms the interdiffusion layer 2 according to the conditions of the cobalt deposition film. This is because the thickness of the cobalt silicide film 3 based on this can be determined as the initial cobalt silicide film thickness, and a calibration curve for each heating rate can be created with this film thickness as the origin.
[0098]
In the third embodiment, cobalt is used as a material for forming silicide. However, during heat treatment, diffusion of nitrogen atoms by ammonia occurs from above the deposited film into the film, and a mutual diffusion preventing layer can be formed at an initial stage of the silicide reaction. If the silicide is stable and has low resistance with metal atoms, the formation and control of the silicide layer using the mutual diffusion preventing layer can be performed with the same processing apparatus.
[0099]
As described above, according to the method for controlling the silicide film thickness according to the third embodiment, it is possible to create a calibration curve for each heating rate with the film thickness of the initial interdiffusion layer as the origin, and to obtain a cobalt film having a desired film thickness. It can be formed by controlling silicide.
[0100]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a method of forming a silicide film, a device for forming the silicide film, and a method of controlling the thickness of the film, in which the thickness of the cobalt silicide film can be formed uniformly.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a semiconductor device in which a mutual diffusion preventing layer is formed in a method of manufacturing a semiconductor device according to a first embodiment.
FIGS. 2A to 2D are cross-sectional views illustrating a method of forming a silicide film according to the first embodiment.
FIG. 3 is a plan sectional view showing a configuration of a silicide film forming apparatus according to a second embodiment.
FIG. 4 is a flowchart showing a procedure for determining an initial silicide film thickness according to a third embodiment;
FIG. 5 is a graph for explaining a relationship between an ammonia introduction time and a heating rate according to a third embodiment.
FIG. 6 is a flowchart showing a procedure for determining a silicide film thickness according to the third embodiment.
FIG. 7 is a graph for explaining a calibration curve for each temperature rise rate of a silicide film thickness according to a third embodiment.
FIGS. 8A to 8D are cross-sectional views illustrating a conventional method for forming a silicide film.
[Explanation of symbols]
1 Mutual diffusion prevention layer
2 Mutual diffusion layer
3 Cobalt silicide film
4 High melting point metal film
5 Silicon substrate
9 Gate electrode
10 Impurity diffusion layer
11 Interdiffusion layer formation chamber
12,13 Heat treatment chamber
14, 15 Load chamber
16 Ammonia gas introducer
17 Oxygen introducer
21 Field oxide film
22 Gate insulating film
23 Sidewall
24 Main load chamber
25 cassette station
150 Silicide film forming device

Claims (25)

A high melting point metal film is formed on a silicon substrate, and an interdiffusion layer of a high melting point metal forming the high melting point metal film and silicon forming the silicon substrate is formed between the high melting point metal film and the silicon substrate. Forming an interdiffusion layer at the interface;
Forming a reciprocal diffusion preventing layer at the interface between the refractory metal film and the interdiffusion layer to prevent further interdiffusion between the refractory metal and the silicon; Heat-treating the silicon substrate on which the interdiffusion layer is formed in an atmosphere containing a nitrogen element. The method for forming a silicide film according to claim 1, wherein the interdiffusion layer heat-treated in the heat treatment step is transformed into a silicide film. The silicon substrate has a gate electrode formed in a gate region, and an impurity diffusion layer formed in each of a source region and a drain region,
2. The method for forming a silicide film according to claim 1, wherein in the step of forming the interdiffusion layer, the refractory metal film is formed so as to cover the gate electrode and the impurity diffusion layer. 4. The interdiffusion layer forming step, wherein the interdiffusion layer is formed at an interface between the gate electrode and the refractory metal film and at an interface between the impurity diffusion layer and the refractory metal film. The method for forming a silicide film according to the above. The method for forming a silicide film according to claim 3, wherein said gate electrode is formed of a polysilicon electrode. The method for forming a silicide film according to claim 1, wherein in the heat treatment step, the mutual diffusion preventing layer is formed to have a thickness of 1 nanometer or more. 2. The method for forming a silicide film according to claim 1, further comprising a removing step of removing said refractory metal film after said heat treatment step. The method for forming a silicide film according to claim 7, further comprising, after the removing step, an additional heat treatment step of performing an additional heat treatment on the silicide film in an atmosphere containing a nitrogen element in order to lower the resistance of the silicide film. The method for forming a silicide film according to claim 1, wherein the atmosphere containing the nitrogen element is a nitrogen or argon atmosphere to which ammonia is added. 2. The method for forming a silicide film according to claim 1, wherein said interdiffusion preventing layer contains silicon nitride. The method for forming a silicide film according to claim 1, wherein the atmosphere containing the nitrogen element is a nitrogen or argon atmosphere to which ammonia and oxygen are added. 2. The method for forming a silicide film according to claim 1, wherein said mutual diffusion preventing layer contains silicon oxynitride. The refractory metal is a metal that does not form a nitrogen compound on its surface when heat-treated at 400 ° C. or more, and the refractory metal film is a film that diffuses nitrogen to the lower surface of the refractory metal film. A method for forming a silicide film according to claim 1. The method according to claim 1, wherein the refractory metal is cobalt. The method of claim 1, wherein the refractory metal film is formed at a substrate temperature of 100 ° C. or more and a thickness of 5 nanometers or more. The method for forming a silicide film according to claim 1, wherein the interdiffusion layer is formed to a thickness of 2 nm or more and 3 nm or less. The method according to claim 1, wherein the heat treatment is performed at a temperature of 400 ° C. or more. A high melting point metal film is formed on a silicon substrate, and an interdiffusion layer of a high melting point metal forming the high melting point metal film and silicon forming the silicon substrate is formed between the high melting point metal film and the silicon substrate. An interdiffusion layer forming chamber for forming at the interface;
Forming a reciprocal diffusion preventing layer at the interface between the refractory metal film and the interdiffusion layer to prevent further interdiffusion between the refractory metal and the silicon; A first heat treatment chamber provided to heat-treat the silicon substrate on which the interdiffusion layer is formed in an atmosphere containing a nitrogen element;
An apparatus for forming a silicide film, comprising: a second heat treatment chamber for performing heat treatment such that the interdiffusion layer heat-treated in the first heat treatment chamber is transformed into a silicide film. The apparatus further includes a first load chamber provided to transfer the silicon substrate on which the refractory metal film and the interdiffusion layer are formed by the interdiffusion layer forming chamber to the first heat treatment chamber in a vacuum state. An apparatus for forming a silicide film according to claim 18. 19. The silicide according to claim 18, further comprising a second load chamber provided to transfer the silicon substrate on which the mutual diffusion preventing layer is formed by the first heat treatment chamber to the second heat treatment chamber in a vacuum state. Film forming equipment. 19. The silicide film forming apparatus according to claim 18, wherein an ammonia gas introduction unit provided for introducing an ammonia gas into an atmosphere containing the nitrogen element is connected to the first heat treatment chamber. 22. The silicide film forming apparatus according to claim 21, wherein an oxygen introduction unit provided for introducing oxygen into the atmosphere containing the nitrogen element is further connected to the first heat treatment chamber. The refractory metal film is cobalt,
19. The silicide film forming apparatus according to claim 18, wherein the interdiffusion layer forming chamber forms the cobalt on the silicon substrate by sputtering. A first step of forming a refractory metal film having a substantially uniform thickness on a semiconductor substrate to form an initial interdiffusion layer of refractory metal and silicon;
A second step of performing a heat treatment for a predetermined time after raising the temperature of the semiconductor substrate to a predetermined temperature while setting an atmosphere containing ammonia with a plurality of temperature raising rate conditions and delaying by a plurality of set time conditions from the start of the temperature raising,
A third step of obtaining a film thickness of a final interdiffusion layer of refractory metal and silicon for each combination of the plurality of temperature raising rate conditions and the plurality of set time conditions. . 25. The method according to claim 24, wherein the refractory metal film is cobalt.

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