JP2766100B2 - Method for removing unreacted gas in reduced pressure vapor phase growth apparatus - Google Patents

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 process of manufacturing a semiconductor device, a film forming process using a low pressure vapor phase epitaxy (LPCVD) apparatus is often used. Hereinafter, the film forming process will be described with reference to FIG.

After the wafer is transferred to the reactor of the LPCVD apparatus, the inside of the reactor is evacuated and then replaced with nitrogen. Next, a silane gas, which is a reaction gas, is subjected to a thermal decomposition reaction to perform a vapor phase growth of a polysilicon film or the like on the wafer. After completion of film formation, 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 over about 20 minutes.

[0004]

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

[0005]

According to the present invention, there is provided a method for removing unreacted gas in a low pressure vapor phase epitaxy apparatus, comprising the steps of: taking out a wafer which has been subjected to vapor phase growth in a reactor; The drawing step and the oxygen substitution step are repeated a plurality of times.

[0006]

Next, embodiments of the present invention will 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 as a reaction gas is introduced, and a polysilicon film, for example, is grown on the wafer by a thermal decomposition reaction. After the film formation is completed, the atmosphere is returned to nitrogen, the atmosphere is restored, and the wafer is discharged from the furnace. Up to this point, it 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 reactor is returned to the atmosphere. Unreacted silane gas in the reaction furnace is decomposed and removed by the repeated oxygen substitution. About 20 minutes is sufficient for the time required for the evacuation and the repeated oxygen substitution. Since this time is almost equal to the time required for cooling the wafer, the processing steps are not longer than in the conventional case.

The LP from which unreacted gas has been removed in this manner
FIG. 2 shows the result (average value) of the number of particles adhering to the wafer when the CVD apparatus was used, together with the case of the conventional example. As is apparent from FIG. 2, according to the present embodiment, even if the process of vapor phase growth is repeated, no dust is generated due to the residual silane, so that the number of particles on the wafer can be significantly reduced.

In the above embodiment, the case where oxygen is used as the replacement gas after the wafer is released from the furnace has been described, but an inert gas such as nitrogen may be used. However, since there is no silane gas decomposition effect unlike oxygen, the number of times of inert gas replacement needs to be larger than in the case of oxygen replacement.

[0011]

As described above, according to the present invention, by repeating the evacuation step and the oxygen substitution step in the reaction furnace by utilizing the time for cooling the wafer, the processing capacity is not reduced and Since the unreacted silane gas remaining in the reactor can be efficiently removed, the number of particles adhering to the wafer can be significantly reduced.
Therefore, the reliability and yield of the semiconductor device can be improved.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining one embodiment of the present invention.

FIG. 2 is a diagram illustrating the relationship between the number of processes and the number of particles for explaining the effect of the embodiment.

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

Claims (1)

(57) [Claims] 1. A reduced-pressure vapor-phase growth apparatus comprising the steps of: discharging a wafer after a vapor-phase growth process in the reaction furnace is completed; and repeating a vacuuming step and an oxygen-substituting step in the reaction furnace a plurality of times. Method of removing unreacted gas.