JPH05109624A - Method for elimination non-reaction gas within reduced-pressure vapor growth device - Google Patents

Abstract

PURPOSE:To enable the number of particles which are adhered to a wafer to be reduced by taking wafers which were subjected to vapor growth treatment out of a reactor and by repeating evacuation, oxygen replacement, or inactive gas replacement for a plurality of times repeatedly. CONSTITUTION:Evacuation is performed after placing a wafer into a reaction reactor, a reaction gas is introduced after an atmosphere is replaced by nitrogen, and then, for example, a polysilicon film is allowed to grow on the wafer. After formation of film is completed, the atmosphere is replaced by oxygen again, atmosphere is recovered, and then the wafer is taken out of the reactor. Then, evacuation and oxygen replacement process are repeated for a plurality of times and then an inside of the reaction reactor is returned to the atmosphere. Repetition of this oxygen replacement eliminates a non-reaction gas within the reaction reactor and can reduce the number of particles which are adhered to the wafer drastically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing unreacted gas in a reduced pressure vapor phase growth apparatus.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a film forming process using a low pressure vapor deposition (LPCVD) device is often used. The film forming process will be described below with reference to FIG.

After the wafer is transferred to the reaction furnace of the LPCVD apparatus, the inside of the reaction furnace is evacuated and then replaced with nitrogen. Next, silane gas, which is a reaction gas, is thermally decomposed to cause vapor phase growth of a polysilicon film or the like on the wafer. After the film formation is completed, the inside of the reaction furnace is replaced with nitrogen again, and after returning to the atmosphere, the wafer is taken out of the furnace and cooled to room temperature for about 20 minutes.

[0004]

In the above-described conventional vapor phase growth process, nitrogen substitution is performed to remove unreacted silane gas remaining in the reaction furnace after forming a film on a wafer. However, in the portion where the flow of nitrogen is insufficient in the reaction furnace, unreacted silane gas remains and adheres to the wall surface or the like, which causes dust generation. For this reason, there is a problem that particles adhere to the wafer in the next step and the reliability and yield of the semiconductor device are reduced.

[0005]

A method of removing unreacted gas in a reduced pressure vapor phase growth apparatus according to the present invention is to remove a wafer on which vapor phase growth processing has been completed in a reaction furnace and then to remove a vacuum in the reaction furnace. The drawing step and the oxygen replacement or inert gas replacement step are repeated a plurality of times.

[0006]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a process chart for explaining one embodiment of the present invention.

First, a wafer is put into a reaction furnace of an LPCVD apparatus, and then a vacuum is drawn. Next, after replacing the atmosphere with nitrogen, a silane gas, which is a reaction gas, is introduced, and, for example, a polysilicon film is grown on the wafer by a thermal decomposition reaction. After the film formation is completed, the atmosphere is returned to nitrogen and the atmosphere is restored to evacuate the wafer. Up to this point, the process is the same as the conventional one.

Next, after the evacuation and oxygen substitution steps are repeated a plurality of times, the inside of the reaction furnace is returned to the atmosphere. By repeating this oxygen substitution, the unreacted silane gas in the reaction furnace is decomposed and removed. About 20 minutes is sufficient as the time required for repeated evacuation and oxygen substitution. Since this time is almost equal to the time required for cooling the wafer, the processing step does not take longer than in the conventional case.

LP from which the unreacted gas has been removed in this way
FIG. 2 shows the result (average value) of the number of particles adhered on the wafer when the CVD apparatus was used, together with the case of the conventional example. As is clear from FIG. 2, according to the present embodiment, even if the vapor phase growth process is repeated, dust generation due to residual silane is eliminated, so that the number of particles on the wafer can be greatly reduced.

In the above embodiment, the case where oxygen is used as the replacement gas after the wafer is evacuated has been described, but an inert gas such as nitrogen may be used. However, since there is no decomposition action of silane gas like oxygen, it is necessary to perform the inert gas replacement more frequently than in the case of oxygen replacement.

[0011]

As described above, according to the present invention, the processing capacity can be improved by repeating the evacuation process in the reaction furnace and the oxygen replacement or inert gas replacement process while utilizing the time for cooling the wafer. Since unreacted silane gas remaining in the reaction furnace can be efficiently removed without lowering the
This has the effect of significantly reducing the number of particles attached to the wafer. Therefore, the reliability and yield of the semiconductor device can be improved.

[Brief description of drawings]

FIG. 1 is a process drawing for explaining an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the number of times of processing and the number of particles for explaining the effect of the embodiment.

FIG. 3 is a process drawing for explaining a conventional example.

Claims (1)

[Claims] 1. A reduced pressure characterized in that after a wafer having undergone vapor phase growth processing in a reaction furnace is evacuated, a vacuum drawing step and an oxygen replacement or inert gas replacement step in the reaction furnace are repeated a plurality of times. A method for removing unreacted gas in a vapor phase growth apparatus.