JP2004221171A - Method of forming nitride film - Google Patents

Abstract

A method of preventing ammonium chloride adhering to an exhaust passage of a CVD apparatus from being granulated, preventing contamination of a CVD reaction chamber by foreign matters caused by the granulated ammonium chloride, and obtaining a uniform nitride film. To provide.
In a method of forming a nitride film by CVD in which an ammonium chloride gas is generated as a reaction by-product, an exhaust pipe connected to a reaction chamber is maintained at a temperature of 50 ° C to 110 ° C to remove the ammonium chloride gas. It collects and deposits ammonium chloride as a layered film.
[Selection] Fig. 2

Description

【００２３】
前記の実施例と比較例との結果にあるように、ＣＶＤよる半導体ウェハへのシリコン窒化膜の形成において、処理圧力を０．０５〜５０Ｔｏｒｒとし、排気配管４を加熱し５０〜１１０℃に保持することは、反応副生成物である塩化アンモニウムに起因する半導体ウェハの不良率を１０％以下に抑制でき、特に、排気配管４を７０〜９０℃に保持すると３％以下に抑制でき、信頼性の高い半導体装置の製造方法である。
【００２４】
【発明の効果】
この発明の窒化膜の形成方法は、反応副生成物として塩化アンモニウムガスを発生するＣＶＤによる窒化膜の形成方法において、反応室に接続された排気配管を５０℃〜１１０℃の温度に保持して、塩化アンモニウムガスを捕集するものであり、排気配管部を１５０℃以上と高い温度に加熱する必要もなく、バルブ、枝配管及びサブバルブなどを含めた排気経路全体を加熱する必要がなく、排気配管の加熱だけで良く、簡単な加熱装置による加熱により、ＣＶＤによるシリコン窒化膜の形成時に発生する反応副生成物である塩化アンモニウムに起因する反応室の汚染を防止でき、信頼性の高い半導体装置が製造できる。
【図面の簡単な説明】
【図１】実施の形態１におけるシリコン窒化膜の形成方法に用いるＣＶＤ装置の構成を示す模式図である。
【図２】実施の形態１において排気配管に捕集され付着した塩化アンモニウムの形状を示する図である。
【図３】排気配管の温度を５０℃未満とした場合の塩化アンモニウムが付着する部分と付着した塩化アンモニウムの形状を示す図である。
【図４】排気配管の温度を１１０℃より大きくした場合の塩化アンモニウムが付着する部分と付着した塩化アンモニウムの形状を示す図である。
【符号の説明】
１ 反応室、２ ガス導入口、３ ガス排気口、４ 排気配管、５ バルブ、６ 枝配管、７ サブバルブ、８ 真空ポンプ、９ 加熱ヒータ、１０ ＣＶＤ装置、１１ ウェハホルダ、１２ 半導体ウェハ、１３ 付着した塩化アンモニウム。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of forming a nitride film by CVD used when manufacturing a semiconductor device, and more particularly to a method of forming a nitride film by CVD in which an ammonium chloride gas is generated as a reaction by-product.
[0002]
[Prior art]
In the formation of a nitride film, particularly a silicon nitride film, by a CVD (Chemical Vapor Deposition) method, dichlorosilane and ammonia are used as reactive gases, and ammonium chloride is generated as a reaction by-product. This ammonium chloride was deposited as a solid substance inside a semiconductor manufacturing apparatus such as a CVD, and was particularly remarkable on a low-temperature wall surface, and adhered much inside an exhaust pipe. When this adhered ammonium chloride accumulates, it peels off from the adhered surface, enters the reaction chamber as particles, and contaminates the semiconductor device.
[0003]
Therefore, in a conventional method for forming a silicon nitride film, a heating means such as a jacket heater is provided in an exhaust pipe connecting a reaction chamber of a CVD apparatus and an exhaust pump, and a joint such as a flange is heated by a tape heater or the like. Means for heating these exhaust passages to about 150 ° C. to prevent ammonium chloride from adhering to the inner surfaces of these exhaust passages, and contaminating the reaction chamber of the CVD apparatus with particles caused by the adhered ammonium chloride. (See, for example, Patent Document 1).
[0004]
[Patent Document 1]
JP-A-09-293708 (page 2, FIG. 1)
[0005]
[Problems to be solved by the invention]
In the conventional method for forming a silicon nitride film, a heating means is provided in an exhaust pipe connecting a reaction chamber of a CVD apparatus and an exhaust pump, and is heated to about 150 ° C. to prevent ammonium chloride from adhering to the inner surface of the exhaust path. However, branch pipes and valves are connected to the exhaust pipe, so that the entire exhaust system must be heated to 150 ° C. or higher in order to prevent the adhesion of ammonium chloride. However, it is difficult to maintain the entire exhaust system uniformly at a high temperature of 150 ° C. or higher. If there is a low-temperature part, the ammonium chloride accumulated in the part becomes particulate and adheres, and this particulate ammonium chloride is removed. There is a problem that the material enters the reaction chamber and causes the generation of foreign matter defects.
[0006]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and prevents ammonium chloride attached to the exhaust passage of a CVD apparatus from being granulated, and prevents foreign matter caused by the granulated ammonium chloride from being used for CVD. It is an object of the present invention to provide a method for forming a nitride film in a semiconductor device without a foreign matter defect while preventing the reaction chamber from being contaminated.
[0007]
[Means for Solving the Problems]
According to the method for forming a nitride film of the present invention, in the method for forming a nitride film by CVD in which an ammonium chloride gas is generated as a reaction by-product, an exhaust pipe connected to a reaction chamber is maintained at a temperature of 50 ° C to 110 ° C. For collecting ammonium chloride gas.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a schematic diagram showing a configuration of a CVD apparatus used for a method of forming a silicon nitride film according to the first embodiment of the present invention.
In FIG. 1, a wafer holder on which a semiconductor wafer is placed is provided in a reaction chamber 1 of a CVD apparatus 10 (not shown). The reaction chamber 1 is provided with a gas inlet 2 for introducing a reactive gas, and on the opposite side of the reaction chamber 1 where the gas inlet 2 is provided, unnecessary reactive gas and reaction by-products are formed. A gas exhaust port 3 for exhausting the ammonium chloride gas is provided. An exhaust pipe 4 is connected to the gas exhaust port 3 by, for example, a flange or the like. The exhaust pipe 4 communicates with a vacuum pump 8. Between the exhaust pipe 4 and the vacuum pump 8, a valve 5 for maintaining the reaction chamber 1 at a vacuum, and a branch pipe 6 and a sub-valve 7 for adjusting the pressure are provided. Further, the exhaust pipe 4 is provided with a heater 9 for maintaining a portion of the exhaust pipe 4 at a predetermined temperature.
[0009]
In the formation of the silicon nitride film by the CVD method in the present embodiment, the semiconductor wafer 12 is placed on the wafer holder 11 in the reaction chamber 1, and the pressure conditions of the reaction chamber 1 and the exhaust pipe 4 are set to 0.05 to 50 Torr. The temperature of the exhaust pipe 4 is maintained at 50 to 110 ° C. by the heater 9. When the temperature of the exhaust pipe 4 is maintained at this temperature, ammonium chloride gas, which is a reaction by-product generated in the reaction chamber 1, is collected and adhered to the exhaust pipe 4. As shown in FIG. 2, the ammonium chloride 13 collected by the exhaust pipe 4 is deposited and adheres to the inner surface of the exhaust pipe 4 in the form of a yellow film, and the adhered film becomes a clean layer.
[0010]
If the temperature of the exhaust pipe 4 is lower than 50 ° C., the collected ammonium chloride gas is solidified as shown in FIG. 3 and becomes fine particles. That is, if the temperature of the exhaust pipe 4 is lower than 50 ° C., the adhered ammonium chloride 13 becomes fine particles, so that it enters the reaction chamber 1 and adheres to the semiconductor wafer 12 in the reaction chamber 1, causing a foreign matter defect. It becomes.
[0011]
If the temperature of the exhaust pipe 4 is higher than 110 ° C., ammonium chloride gas, which is a reaction by-product generated in the reaction chamber 1, is collected and adhered to the exhaust pipe 4, but the temperature of the exhaust pipe 4 is high. A part of the ammonium chloride 13 attached to the exhaust pipe 4 in a layer form is re-vaporized. The re-vaporized ammonium chloride gas comes into contact with the vicinity of the unheated valve 5 and the branch pipe 6, and if the temperature is lower than 50 ° C., the ammonium chloride 13 becomes particulate as shown in FIG. The particles soar up and enter the reaction chamber 1 and adhere to the semiconductor wafer 12 in the reaction chamber 1, causing foreign matter defects.
[0012]
However, in the method of forming a silicon nitride film according to the present embodiment, the exhaust pipe 4 of the CVD apparatus is heated by the heater 9 and is maintained at a temperature of 50 to 110 ° C. Ammonium chloride gas, which is a substance, can be collected by the exhaust pipe 4 and adhered as a layered film.
Since the temperature of the exhaust pipe 4 is 50 ° C. or higher, the adhered ammonium chloride does not become particulate and does not contaminate the inside of the reaction chamber 1. Further, since the ammonium chloride gas is mostly collected in the exhaust pipe 4, it does not adhere to other unheated exhaust paths such as the valve 5 and the branch pipe 6.
Further, since the exhaust pipe 4 has a temperature of 110 ° C. or lower, the adhered ammonium chloride 13 may re-evaporate from the exhaust pipe 4 and adhere to other unheated exhaust paths such as the valve 5 and the branch pipe 6. Absent.
That is, since the ammonium chloride gas does not come into contact with the exhaust passage portion at a temperature lower than 50 ° C. other than the exhaust pipe 4, no particulate ammonium chloride is generated and the inside of the reaction chamber 1 is not contaminated.
[0013]
In the method for forming a silicon nitride film in the present embodiment, the pressure in the reaction chamber 1 and the exhaust pipe 4 is 0.05 to 50 Torr. If the pressure in this portion is maintained at less than 0.05 Torr, the concentration of the reactive gas decreases, and it takes time to form the silicon nitride film, and the productivity decreases.
If the pressure in the exhaust pipe 4 is higher than 50 Torr, ammonium chloride adheres to the wall of the reaction chamber 1 and the semiconductor wafer 12 is contaminated.
[0014]
In the present embodiment, the heater 9 is used as a heating unit for maintaining the exhaust pipe 4 at a temperature of 50 to 110 ° C. However, heating by a heat medium may be performed.
[0015]
In the method for forming a silicon nitride film in the present embodiment, it is not necessary to heat the exhaust pipe to a high temperature of 150 ° C. or higher, and it is not necessary to heat the entire exhaust path including valves, branch pipes, sub-valves, and the like. Since only heating for maintaining the temperature of the pipe 4 at a temperature of 50 to 110 ° C. is sufficient, heating by a simple heating device causes a reaction chamber caused by ammonium chloride as a reaction by-product generated when a silicon nitride film is formed by CVD. Contamination can be prevented, defects due to foreign matter on the semiconductor wafer can be prevented, and a highly reliable semiconductor device can be manufactured.
[0016]
【Example】
Next, the effects of the method for forming a silicon nitride film of the present invention will be described with reference to examples.
[0017]
Embodiment 1 FIG.
Using the apparatus shown in FIG. 1, a semiconductor wafer 12 (not shown) is placed on a wafer holder 11 (not shown) in the reaction chamber 1, and dichlorosilane and ammonia are used as source gases at a predetermined processing pressure. Then, a CVD process is performed at 0.45 Torr to form a silicon nitride film on the semiconductor wafer 11. At this time, the exhaust pipe 4 is kept at 110 ° C. by heating, and ammonium chloride gas as a reaction by-product is collected by the exhaust pipe 4.
Under these conditions, 1000 semiconductor wafers were processed, the defect rate due to foreign matter caused by ammonium chloride was determined, and the shape of ammonium chloride attached to the exhaust pipe 4 at the holding temperature was observed. It was confirmed whether ammonium chloride had adhered to the exhaust path. As shown in Table 1, the defect rate of the semiconductor wafer was 8%, the shape of ammonium chloride attached to the exhaust pipe 4 was a film, and no adhesion of ammonium chloride was observed in other exhaust paths.
[0018]
Embodiments 2-4.
A silicon nitride film is formed on a semiconductor wafer in the same manner as in Example 1 except that the temperature of the exhaust pipe 4 is maintained at the temperature shown in Table 1.
Under these conditions, 1000 semiconductor wafers were processed, the defect rate due to foreign matter caused by ammonium chloride was determined, and the shape of ammonium chloride attached to the exhaust pipe 4 at the holding temperature was observed. It was confirmed whether ammonium chloride had adhered to the exhaust path. Table 1 shows the percentage of defective semiconductor wafers, the shape of ammonium chloride adhering to the exhaust pipe 4, and the presence or absence of ammonium chloride adhering to other exhaust passages.
[0019]
Examples 5-6.
A silicon nitride film is formed on a semiconductor wafer in the same manner as in Example 1, except that the CVD processing pressure is set to the pressure shown in Table 1.
Under these conditions, 1000 semiconductor wafers were processed, the defect rate due to foreign matter caused by ammonium chloride was determined, and the shape of ammonium chloride attached to the exhaust pipe 4 at the holding temperature was observed. It was confirmed whether ammonium chloride had adhered to the exhaust path. Table 1 shows the percentage of defective semiconductor wafers, the shape of ammonium chloride adhering to the exhaust pipe 4, and the presence or absence of ammonium chloride adhering to other exhaust passages.
[0020]
Comparative Examples 1-2.
A silicon nitride film is formed on a semiconductor wafer in the same manner as in Example 1 except that the temperature of the exhaust pipe 4 is maintained at the temperature shown in Table 1.
Under these conditions, 1000 semiconductor wafers were processed, the defect rate due to foreign matter caused by ammonium chloride was determined, and the shape of ammonium chloride attached to the exhaust pipe 4 at the holding temperature was observed. It was confirmed whether ammonium chloride had adhered to the exhaust path. Table 1 shows the percentage of defective semiconductor wafers, the shape of ammonium chloride adhering to the exhaust pipe 4, and the presence or absence of ammonium chloride adhering to other exhaust passages.
[0021]
Comparative Example 3
A silicon nitride film is formed on a semiconductor wafer 12 in the same manner as in Example 1 except that the CVD processing pressure is set to 55 Torr shown in Table 1.
Under these conditions, 1000 semiconductor wafers were processed, the defect rate due to foreign matter caused by ammonium chloride was determined, and the shape of ammonium chloride attached to the exhaust pipe 4 at the holding temperature was observed. It was confirmed whether ammonium chloride had adhered to the exhaust path. Table 1 shows the percentage of defective semiconductor wafers, the shape of ammonium chloride adhering to the exhaust pipe 4, and the presence or absence of ammonium chloride adhering to other exhaust passages.
[0022]
[Table 1]

[0023]
As shown in the results of the above example and comparative example, in forming a silicon nitride film on a semiconductor wafer by CVD, the processing pressure was set to 0.05 to 50 Torr, and the exhaust pipe 4 was heated and maintained at 50 to 110 ° C. By doing so, the defect rate of the semiconductor wafer caused by ammonium chloride which is a reaction by-product can be suppressed to 10% or less, and in particular, it can be suppressed to 3% or less when the exhaust pipe 4 is kept at 70 to 90 ° C. This is a method for manufacturing a semiconductor device with high reliability.
[0024]
【The invention's effect】
According to the method for forming a nitride film of the present invention, the exhaust pipe connected to the reaction chamber is maintained at a temperature of 50 ° C. to 110 ° C. in the method of forming a nitride film by CVD that generates ammonium chloride gas as a reaction by-product. , Collecting ammonium chloride gas, there is no need to heat the exhaust pipe section to a high temperature of 150 ° C. or higher, and there is no need to heat the entire exhaust path including valves, branch pipes and sub-valves. It is only necessary to heat the piping, and by heating with a simple heating device, it is possible to prevent contamination of the reaction chamber caused by ammonium chloride, which is a reaction by-product generated when a silicon nitride film is formed by CVD, and a highly reliable semiconductor device. Can be manufactured.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of a CVD apparatus used for a method for forming a silicon nitride film in a first embodiment.
FIG. 2 is a view showing a shape of ammonium chloride collected and attached to an exhaust pipe in the first embodiment.
FIG. 3 is a diagram showing a portion where ammonium chloride adheres and a shape of the adhered ammonium chloride when the temperature of an exhaust pipe is set to less than 50 ° C.
FIG. 4 is a diagram showing a portion where ammonium chloride adheres and a shape of the adhered ammonium chloride when the temperature of the exhaust pipe is set higher than 110 ° C.
[Explanation of symbols]
Reference Signs List 1 reaction chamber, 2 gas introduction port, 3 gas exhaust port, 4 exhaust pipe, 5 valve, 6 branch pipe, 7 sub-valve, 8 vacuum pump, 9 heater, 10 CVD device, 11 wafer holder, 12 semiconductor wafer, 13 attached Ammonium chloride.

Claims (2)

In a method for forming a nitride film by CVD in which an ammonium chloride gas is generated as a reaction by-product, a nitride film for collecting an ammonium chloride gas by maintaining an exhaust pipe connected to a reaction chamber at a temperature of 50 ° C to 110 ° C Formation method. 2. The method according to claim 1, wherein the processing pressure of the CVD is 0.05 to 50 Torr.

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