JP2001085690A - Method for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower the resistance of a gate electrode and to suppress the abnor mal oxidation of the gate electrode. SOLUTION: An amorphous silicon film 12 is formed on a gate oxide film 11. After that, a polysilicon film 13 is formed on the amorphous silicon film 12 continuously inside the same chamber. After that, a tungsten silicon film 14 is formed on the polysilicon film 13. In this manner, in a gate electrode 17, the polysilicon film 13 which can increase the crystal-plane strength ratio of the tungsten silicon film 14 if formed under the tungsten silicon film 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a CV of a fine wiring layer.
The present invention relates to film formation using a D (Chemical Vapor Deposition) method, and more particularly to a method for manufacturing a semiconductor device using a silicon gate electrode.

[0002]

2. Description of the Related Art Conventionally, a gate electrode having a laminated structure including a polysilicon film and a tungsten silicon film has been used to suppress the resistance of the gate electrode. A method for manufacturing such a gate electrode will be described below.

First, as shown in FIG. 8, a gate oxide film 21 is formed on a P-type silicon substrate 20, for example, and an amorphous silicon film 22 is formed on the gate oxide film 21. Here, when the amorphous silicon film 22 is formed, PH ₃ is simultaneously flown, and P (phosphorus) is injected into the amorphous silicon film 22.

Next, after being transferred to another chamber by vacuum, for example, a sputtering method or a CVD (Chemical Vapor Dep.
osition), a tungsten silicon film 24 is formed on the amorphous silicon film 22. At this time, R
According to the BS (Rutherford backscattering method) analysis, the composition X (X = silicon / tungsten) of the tungsten silicon film 24 was 2.61.

Next, a thermal oxide film 25 is formed on the tungsten silicon film 24, and a resist film 26 is formed on the thermal oxide film 25 and patterned.

[0006] Next, as shown in FIG.
Using thermal mask as a mask, thermal oxide film 25 is removed to form a gate pattern. After that, the resist film 26 is removed.

Next, as shown in FIG. 10, using the thermal oxide film 25 formed in the gate pattern as a mask, the tungsten silicon film 24 and the amorphous silicon film 22 are removed, and the surface of the gate insulating film 21 is exposed. A gate electrode 27 is formed.

Next, post-oxidation is performed to remove damage caused on the gate insulating film 21. As shown in FIG. 11, an oxide film 28 is formed on the side surfaces of the amorphous silicon film 22 and the tungsten silicon film 24. Is done. On this occasion,
According to the RBS analysis, the composition X of the tungsten silicon film 24 changes to about 2.40 because the crystal tends to approach a stable state (X = 2.0).

[0009]

The resistance of the gate electrode 27 is determined by the composition X of the tungsten silicon film 24. That is, the lower the composition X, the lower the resistance of the gate electrode 27 can be. Therefore, as the amount of tungsten in the tungsten silicon film 24 increases, the gate electrode 2
7 has low resistance.

On the other hand, in the post-oxidation step,
Tungsten silicon due to the silicon in the silicon film 24
Oxide film 18 is formed on the side surface of film 24. But Tan
If the amount of tungsten in the gustene silicon film 24 is large,
If the composition X is low in silicon,
Instead of silicon being supplied to the side surface of the silicon film 24,
Is supplied. As a result, the tungsten silicon
WO on the side of the con film 24 _ThreeAn oxide is formed. This W
O_ThreeOxides have a large volume expansion coefficient. Because of this, Tangs
The ten silicon film 24 (gate electrode 27) is destroyed.
Abnormal phenomenon of tungsten being oxidized abnormally
Called oxidation. Accordingly, the resistance of the gate electrode 27 is reduced.
In order to achieve this, the tungsten in the tungsten silicon film 24
Adjust the amount of ten so that the composition X does not cause abnormal oxidation.
Is important.

As described above, in consideration of both the lowering of the resistance of the gate electrode and the suppression of abnormal oxidation, the tungsten silicon film 2
It is very difficult to change the composition X of No. 4.

Therefore, as a method for suppressing abnormal oxidation without changing the composition of the tungsten silicon film 24, the crystal plane intensity ratio of the tungsten silicon film 24 ((0
There is a report that the oxidation of the tungsten silicon film 24 can be suppressed by increasing the (02) plane / (101) plane).

The tungsten silicon film 24 is usually in a polycrystalline state having several crystal planes. When the tungsten silicon film 24 is post-oxidized, the tetragonal (0
Several crystal planes such as the (02) plane and the (101) plane grow. Here, the lattice spacing of the (002) plane is (101)
Reaction with oxygen is very unlikely to occur because it is smaller than the surface. Therefore, by growing the (002) plane and increasing the crystal plane intensity ratio, an oxidation-resistant film can be obtained without changing the composition X of the tungsten silicon film 24.

However, it is usually very difficult to increase the crystal plane strength ratio. As one method of increasing the crystal plane intensity ratio, there is a method of increasing the temperature at the time of forming the tungsten silicon film 24 to around 650 ° C.
That is, the change in the crystal plane intensity ratio performed in the post-oxidation step is performed during the formation of the tungsten silicon film 24. Thereby, the oxidation-resistant tungsten silicon film 24 may be obtained.

However, the film forming temperature is limited by the film forming apparatus, and the tungsten silicon film 24 is currently a parameter having a low degree of freedom. in this way,
There has been no method that can control the crystal plane.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a method of manufacturing a semiconductor device capable of reducing the resistance of a gate electrode and suppressing abnormal oxidation. To provide.

[0017]

The present invention uses the following means to achieve the above object.

According to the method of manufacturing a semiconductor device of the present invention, a step of forming a gate oxide film on a semiconductor substrate, a step of forming an amorphous silicon film on the gate oxide film, and a step of forming a polysilicon film on the amorphous silicon film Forming, forming a tungsten silicon film on the polysilicon film, forming a thermal oxide film on the tungsten silicon film, forming a resist film on the thermal oxide film and patterning. Using the patterned resist film as a mask, removing the thermal oxide film to form a gate pattern, removing the resist film, and masking the thermal oxide film processed into the gate pattern. Removing the tungsten silicon film, the polysilicon film, and the amorphous silicon film to form a gate; And forming a pole.

The amorphous silicon film and the polysilicon film may be formed continuously in the same chamber.

In the step of forming the polysilicon film, the deposition rate of the polysilicon film is lower than the deposition rate of the amorphous silicon film. Further, the deposition rate of the polysilicon film may be 150 ° / min or less.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

First, as shown in FIG. 1, a gate oxide film 11 having a thickness of, for example, 100 ° is formed on a P-type silicon substrate 10, for example. Next, an amorphous silicon film 12 having a thickness of, for example, 1000 ° is formed on the gate oxide film 11 by a single-wafer furnace. At this time, PH ₃ is caused to flow at the same time, and P is injected into the amorphous silicon film 12.
At this time, the concentration of P is, for example, 1.8 × 10 ²⁰ cm ⁻³ .

Next, a polysilicon film 13 having a thickness of, for example, 150 ° is formed on the amorphous silicon film 12 continuously in the same chamber. The formation of the polysilicon film 13 is not limited to being formed continuously with the amorphous silicon film 12, but may be formed separately.

FIG. 6 shows the relationship between the film forming speed of the amorphous silicon film and the polysilicon film and the average particle diameter. As shown in FIG. 6, when forming the polysilicon film 13 from the amorphous silicon film 12, the film formation rate is gradually reduced, and when forming the polysilicon film 13, the film formation rate is reduced to 150 ° / min or less. In this case, the average grain size of the polysilicon is about 550 °.

Then, after being vacuum-transferred to another chamber,
For example, a tungsten silicon film 14 having a thickness of, for example, 500 ° is formed on the polysilicon film 13 by a sputtering method or a CVD method. At this time, according to the RBS analysis, the composition X of the tungsten silicon film was 2.61.

Next, as shown in FIG. 2, a thermal oxide film 15 is formed on the tungsten silicon film 14, and a resist film 16 is formed on the thermal oxide film 15 and patterned.

Next, as shown in FIG.
Is used as a mask, thermal oxide film 15 is removed and processed into a gate pattern. After that, the resist film 16 is removed.

Next, as shown in FIG. 4, using the thermal oxide film 15 processed into the gate pattern as a mask, the tungsten silicon film 14, the polysilicon film 13, and the amorphous silicon film 12 are removed. The surface is exposed, and a gate electrode 17 is formed.

Next, post-oxidation is performed to remove damage caused on the gate insulating film 11. Specifically, first, in order to reduce the resistance of the gate electrode 17, in an inert gas, the processing temperature is, for example, 800 ° C., and the processing time is, for example, 3 hours.
At 0 minutes, the whole is heated. Next, in order to recover the damage of the gate oxide film 11, the processing temperature is, for example, 1000 ° C., and the processing time is, for example, 8 in an oxygen atmosphere of a high-speed heating furnace.
At 0 seconds, the whole is heated.

As a result, excess silicon is discharged from the tungsten silicon film 14 and the like, and as shown in FIG. 18 are formed. Here, the thickness of oxide film 18 is not limited to 60 °, and may be any thickness as long as damage to the lower end of gate electrode 17 can be removed.

After such a heating step, the crystal state of the tungsten silicon film 14 is as follows.

FIG. 7 shows the relationship between the average grain size of the polysilicon film 13 and the crystal plane intensity ratio of the tungsten silicon film 14. Here, the horizontal axis indicates the average grain size in the process of forming the polysilicon film 13. The vertical axis indicates the tungsten silicon film 14 formed on the polysilicon film 13.
3 shows the crystal plane strength ratio after the heat step.

As shown in FIG. 7, in the process of forming the polysilicon film 13, the average grain size gradually increases, and amorphous silicon is changed to polysilicon. Accordingly, the crystal plane intensity ratio of tungsten silicon film 14 increases. In particular, the crystal plane intensity ratio sharply increases from the average grain size of 550 ° which becomes the polysilicon film 13.

As described above, the present invention is characterized in that the polysilicon film 13 capable of increasing the crystal plane intensity ratio of the tungsten silicon film 14 is formed under the tungsten silicon film 14.

According to the above-described embodiment of the present invention, the deposition rate is set to 150 ° / mi under the tungsten silicon film 14.
n or less and the average grain size is 550 ° or more.
3 is formed. By controlling the average grain size of the polysilicon film 13 in this way, it is possible to particularly control the (002) crystal plane having high oxidizability after the heating step, and to increase the crystal plane intensity ratio of the tungsten silicon film 14. Therefore, the abnormal oxidation of the tungsten silicon film 14 can be suppressed, and the characteristic deterioration of the gate electrode can be suppressed.

On the gate oxide film 11, an amorphous silicon film 12 is formed. The average particle size of the amorphous silicon in the amorphous silicon film 12 increases after the heating step. Therefore, the diffusion of P in the amorphous silicon film 12 to the outside can be suppressed. Therefore, an increase in the resistance of the amorphous silicon film 12 can be suppressed, so that the resistance of the gate electrode can be reduced. Further, diffusion of F from the tungsten silicon film 14 to the gate oxide film 11 can be suppressed. Therefore, deterioration of the gate oxide film 11 can be suppressed.

The present invention has a two-layer structure in which an amorphous silicon film 12 and a polysilicon film 13 are formed under a tungsten silicon film 14. This two-layer structure is realized by changing the material supply ratio in one chamber. For this reason, a low-resistance gate electrode that can be used for next-generation products can be manufactured using existing equipment. Further, as described above, the characteristics of the conventional amorphous silicon film do not deteriorate even in the two-layer structure.

As a result, the composition X of tungsten silicon, which causes abnormal oxidation of the tungsten silicon film in the thermal process, was about 2.40 conventionally, but according to the present invention, there is no abnormal oxidation up to 2.28. Make sure that. In addition, the specific resistance in the state of a solid film (formed) is 83
μΩ · cm, but according to the present invention, 65 μΩ · cm
Could be lowered. Therefore, by using the method for manufacturing a gate electrode of the present invention, the applicable range of a product can be greatly expanded.

In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0040]

As described above, according to the present invention, it is possible to provide a method of manufacturing a semiconductor device capable of reducing the resistance of a gate electrode and suppressing abnormal oxidation.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a manufacturing process of a semiconductor device according to the present invention.

FIG. 2 is a cross-sectional view showing a manufacturing step of the semiconductor device according to the present invention, following FIG. 1;

FIG. 3 is a sectional view showing a manufacturing step of the semiconductor device according to the present invention, following FIG. 2;

FIG. 4 is a cross-sectional view showing a manufacturing step of the semiconductor device according to the present invention, following FIG. 3;

FIG. 5 is a sectional view showing a manufacturing step of the semiconductor device according to the present invention, following FIG. 4;

FIG. 6 is a diagram showing conditions for forming an amorphous silicon film and a polysilicon film.

FIG. 7 is a diagram showing an average grain size of a polysilicon film and a crystal plane intensity ratio of a tungsten silicon film.

FIG. 8 is a sectional view showing a manufacturing process of a semiconductor device according to a conventional technique.

FIG. 9 is a sectional view showing a manufacturing step of the semiconductor device according to the related art, following FIG. 8;

FIG. 10 is a cross-sectional view showing a manufacturing step of the conventional semiconductor device, following FIG. 9;

FIG. 11 is a cross-sectional view showing a manufacturing step of the conventional semiconductor device, following FIG. 10;

[Explanation of symbols]

 Reference Signs List 10: silicon substrate, 11: gate insulating film, 12: amorphous silicon film, 13: polysilicon film, 14: tungsten silicon film, 15: thermal oxide film, 16: resist film, 17: gate electrode, 18: oxide film

Claims (4)

[Claims] A step of forming a gate oxide film on a semiconductor substrate; a step of forming an amorphous silicon film on the gate oxide film; a step of forming a polysilicon film on the amorphous silicon film; Forming a tungsten silicon film on the silicon film; forming a thermal oxide film on the tungsten silicon film; forming a resist film on the thermal oxide film and patterning; and forming the patterned resist. Removing the thermal oxide film to form a gate pattern by using the film as a mask; removing the resist film; using the thermal oxide film processed to the gate pattern as a mask to form the tungsten silicon film; Removing the polysilicon film and the amorphous silicon film to form a gate electrode. The method of manufacturing a semiconductor device according to claim and. 2. The method according to claim 1, wherein said amorphous silicon film and said polysilicon film are continuously formed in the same chamber. 3. The method according to claim 1, wherein, in the step of forming the polysilicon film, a deposition rate of the polysilicon film is lower than a deposition rate of the amorphous silicon film. . 4. The film forming rate of the polysilicon film is 15
4. The method for manufacturing a semiconductor device according to claim 3, wherein the temperature is 0 ° / min or less.