JPH07249618A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a forming method of a silicon nitride film wherein the improvement of oxidation resistance and high speed of film formation are compatible with each other. CONSTITUTION:A silicon nitride film is formed by a thermal CVD method using silane and ammonia as material gas, at a temperature lower than or equal to 630 deg.C and a pressure higher than or equal to 10Torr. In this case, higher order silane such as disilane and trisilane may be used instead of silane as the material gas, and hydrazine or derivative of hydrazine such as monomethylhydrazine and trimethylhydrazine may be used instead of ammonia as the material gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having a step of forming a silicon nitride film by a chemical vapor deposition method. In recent years in the manufacturing process of semiconductor devices, the importance of the silicon nitride film is increasing, and higher performance is required.

[0002]

2. Description of the Related Art In a DRAM, a double-layer film obtained by thinly oxidizing the surface of a thermal CVD silicon nitride film is used as a capacitor insulating film. Species impermeable properties (oxidation resistance) are required.

A conventional silicon nitride film is formed by a batch type film forming apparatus. In order to maintain a uniform film thickness distribution between batches and within a batch, hydrogen chloride silane and ammonia are used as source gases, The film is formed at a pressure of about 0.8 Torr. However, when the film formation temperature is lowered to improve the oxidation resistance, the film formation rate decreases and the amount of by-product ammonium chloride that adheres to the inner wall of the film formation device increases, thus cleaning the film formation device. The number of times increased, and in an extreme case, ammonium chloride clogged the pipe to cause pump down, resulting in deterioration of throughput.

[0004]

Therefore, there has been a problem that the improvement of the oxidation resistance and the high film forming rate cannot be achieved at the same time, and the throughput cannot be improved. In view of the above points, an object of the present invention is to provide a method for forming a silicon nitride film capable of achieving both improved oxidation resistance and high film formation rate.

[0005]

In the method of manufacturing a semiconductor device according to the present invention, silane and ammonia are used as source gases, the film forming temperature is 630 ° C. or less, and the film forming pressure is 10 T.
A process of forming a silicon nitride film by the thermal CVD method at or or higher is adopted.

In this case, higher order silane can be used in place of the source gas silane, and hydrazine or its derivative can be used in place of the source gas ammonia.

[0007]

In the present invention, as described above, silane and ammonia are used as the source gas, and the silicon nitride film is formed by the thermal CVD method at the film forming temperature of 630 ° C. or less and the film forming pressure of 10 Torr or more. A silicon nitride film having high oxidation resistance can be obtained without increasing by-products and lowering the film formation temperature.

In this case, substantially the same effect can be obtained by using a higher order silane instead of the source gas silane and using hydrazine or a derivative thereof instead of the source gas ammonia.

[0009]

EXAMPLES Examples of the present invention will be described below. Figure 1
It is explanatory drawing of the film-forming apparatus for enforcing the manufacturing method of the semiconductor device of this invention. In this figure, 1 is a bell jar,
Reference numeral 2 is a gas introduction pipe, 3 is a gas shower, 4 is a support, 5 is a heater, 6 is a wafer, and 7 is an exhaust pipe.

A film forming apparatus for carrying out the method of manufacturing a semiconductor device according to the present invention comprises a bell jar 1 having a gas introducing pipe 2 and an exhaust pipe 7, and a heater 5 made of graphite coated with SiC by a supporting base 4. The wafer 6 can be placed on the wafer 6, and the reaction gas is emitted by the gas shower 3 made of graphite coated with SiC on the wafer 6. As this film forming apparatus, a single wafer type low pressure CVD apparatus can be used.

Using this film forming apparatus, a thermal CVD silicon nitride film was deposited on a silicon substrate at a film forming temperature of 500 ° C. and a film forming pressure of 100 Torr. When the source gas is silane 5 sccm and ammonia 300 sccm, the film forming rate is about 30 Å, which is the same value as in the case of the film forming method using the conventional batch type film forming apparatus.

Although a carrier gas is not used in this embodiment, nitrogen, hydrogen, argon or the like can be used as a carrier gas. Further, in this example, silane and ammonia were used as the source gas, but higher silane such as disilane and trisilane instead of silane, hydrazine or monomethylhydrazine instead of ammonia, or a derivative of hydrazine such as dimethylhydrazine. You can also

When a higher silane such as disilane or trisilane is used in place of silane, the same effect as in the case of using silane is produced, and hydrazine or a derivative of hydrazine such as monomethylhydrazine or dimethylhydrazine is used in place of ammonia. When using, the same effect as that when using ammonia is produced.

FIG. 2 is a diagram for explaining the relationship between the substrate temperature and the film formation rate. According to this figure, as the substrate temperature decreases from about 800 ° C, the film formation rate gradually decreases to 600 ° C.
Although the film formation speed decreases abruptly when decreasing from about
It can be seen from the conditions of the substrate temperature for obtaining the necessary oxidation resistance described below that the practicability is maintained even at 630 ° C. or lower depending on the application field.

After depositing silicon nitride films having different film thicknesses of about 10 to 100 Å on the wafer, wet oxidation (900 ° C., 100 minutes) was collectively performed to measure the film thickness before and after the oxidation. If the silicon nitride film loses its oxidation resistance, the oxidizing species generated by the decomposition of oxygen or ozone will pass through the silicon nitride film and oxidize the underlying silicon substrate. It increases sharply compared to before.

FIG. 3 is an explanatory view of the relationship between the thickness of the deposited silicon nitride film and the thickness of the oxidized film. As shown in this figure, the substrate temperature in the deposition process is 800 ° C.
In the case of No. 3, it is shown that the thickness of the deposited silicon nitride film is about 90 Å, the thickness of the oxidized film rapidly increases, and the oxidation resistance of the silicon nitride film is lost. Similarly,
Substrate temperature in deposition process is 500 ℃ or 625 ℃
In the case of No. 2, it is indicated that the thickness of the deposited silicon nitride film was about 50 Å and the thickness of the oxidized film rapidly increased, and the oxidation resistance of the silicon nitride film was lost.

From this fact and the related measurement, when the film formation temperature of the silicon nitride film is set to 630 ° C. or lower, the film thickness becomes 5
Even at 0Å, high oxidation resistance can be obtained.

FIG. 4 is a diagram for explaining the relationship between the total pressure of the film forming atmosphere and the film forming rate. According to this figure, when the total pressure of the film formation atmosphere of the silicon nitride film is increased, the film formation rate of the silicon nitride film is gradually increased to about 10 Torr or more, especially 5 torr.
It can be seen that saturation occurs at 0 Torr or higher.

[0019]

As described above, according to the present invention,
Without lowering the film formation rate and increasing by-products,
A silicon nitride film having high oxidation resistance can be obtained, and as a result, it greatly contributes to the improvement of the characteristics of the semiconductor device and the improvement of the throughput.

[Brief description of drawings]

FIG. 1 is an explanatory view of a film forming apparatus for carrying out a semiconductor device manufacturing method of the present invention.

FIG. 2 is an explanatory diagram of a relationship between a substrate temperature and a film formation rate.

FIG. 3 is an explanatory diagram of a relationship between a film thickness of a deposited silicon nitride film and a film thickness of an oxidized film.

FIG. 4 is an explanatory diagram of a relationship between a total pressure of a film forming atmosphere and a film forming rate.

[Explanation of symbols]

 1 bell jar 2 gas introduction pipe 3 gas shower 4 support 5 heater 6 wafer 7 exhaust pipe

Claims (3)

[Claims] 1. A silane and ammonia are used as a source gas,
A method of manufacturing a semiconductor device, comprising a step of forming a silicon nitride film by a thermal CVD method at a film forming temperature of 630 ° C. or less and a film forming pressure of 10 Torr or more. 2. The method for manufacturing a semiconductor device according to claim 1, wherein high-order silane is used instead of silane as a source gas. 3. The method for manufacturing a semiconductor device according to claim 1, wherein hydrazine or a derivative thereof is used in place of ammonia as a raw material gas.