JPS6265414A - Reduced pressure cvd equipment - Google Patents

Abstract

PURPOSE:To reduce deterioration of oil used in an exhaust vacuum pump and decrease faults in the vacuum pump to improve its reliability, by effectively lowering the temperature of air in a heat exchanger when high-temperature air at the atmospheric pressure is exhausted through an auxiliary exhaust pipe. CONSTITUTION:After a wafer 6 is introduced into a reaction pipe 1, an exhaust valve 10 is closed and an auxiliary exhaust valve 11 is opened so that the air inside the reaction pipe 1 is slowly exhausted through an auxiliary exhaust pipe 9. At this time the high-temperature air at the atmospheric pressure in the reaction pipe 1 is heat-exchanged in a heat exchanger 16 installed on the auxiliary exhaust pipe 9. Therefore, the temperature becomes low enough not to promote deterioration of oil used n an exhaust mechanical booster 14 and a rotary pump 15. And when the pressure inside the reaction pipe 1 becomes comparatively low, the auxiliary exhaust valve 11 is closed and the exhaust valve 10 is opened so that exhaust pipe 8 during reaction, decrease in heat exchange efficiency is not caused by the reaction products attaching to the heat exchanger 16. Resultantly, reliability can be improved throughout the whole device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a reduced pressure CVD apparatus, and particularly to a reduced pressure CVD apparatus having high reliability.

[Background of the invention]

Regarding low pressure CVD equipment, see "Vacuum" pages 113 to 1.
18 (March 1985) by Kurokawa and Shibata entitled "Current situation and technical issues in reduced pressure CvD equipment". FIG. 1 shows a conventional batch type reduced pressure CVD apparatus. In this cycle, after the wafer 6 is introduced into the reaction tube 1, the air inside the reaction tube 1 is pumped through a mechanical booster 14. The exhaust gas is then evacuated using the rotary pump 15, and nitrogen gas is introduced from the gas supply section 3 through the gas valve 4 to replace it with air.The reaction gas is introduced from the gas supply section 3 through the gas valve 4 to cause a reaction, and then the gas is replaced with nitrogen again. The atmosphere is then introduced through the leak valve 13 to return the reaction tube 1 to an atmospheric pressure state, and the wafer 6 is taken out. In the process of exhausting the air inside the reaction tube 1 after loading the wafer 6, in a pressure region close to atmospheric pressure, it is necessary to slowly exhaust the air to avoid building up dust inside the reaction tube 1, so a single exhaust pipe is used. Close the exhaust valve 1o on the side 8 and open the auxiliary exhaust valve 11 on the side 9 of the auxiliary exhaust pipe, which has a smaller diameter than the exhaust pipe, to exhaust the air. 0 When the pressure inside the reaction tube 1 becomes low to a certain extent, open the auxiliary exhaust valve 11. The pressure inside the reaction tube 1, which is closed and exhausted through the exhaust pipe 8 by opening the exhaust valve 10, is atmospheric pressure after the wafer 6III is introduced, and is in a reduced pressure state during the reaction.

The reaction tube 1 is constantly heated by a heater 2, and the temperature of the reaction tube wall is several hundred degrees Celsius. Therefore, in the process of slowly exhausting the air after loading the wafer 6, the pressure is high and the temperature is high during the cycle, so the amount of heat of the gas to be exhausted is large, and when this gas flows into the mechanical booster 14 and the rotary pump 15, the pump Accelerates the deterioration of the oil used. Oil deterioration can lead to pump failure and reduced pressure C.
This leads to a decrease in the reliability of the vDi device. The conventional apparatus includes a cooling trap 7, which is used to capture the products during the reaction, and as the apparatus is used for a long period of time, the reaction products accumulate.

Since the cooling efficiency was even lower, it was not sufficient to cool the high temperature air at atmospheric pressure after the wafer 6 was carried into the reaction tube 1.

[Purpose of the invention]

An object of the present invention is to provide a highly reliable low pressure CVD system.

[Summary of the invention]

In the batch low-pressure CVD cycle, after the wafer is transferred into the reaction tube, high-temperature air at atmospheric pressure in the reaction tube is transferred to an auxiliary pipe that has a smaller diameter than the main exhaust pipe to prevent dust from building up inside the reaction tube. At this time, the air flowing into the vacuum pump for exhaust is at high pressure and high temperature during the cycle, so the gas to be exhausted has a large calorific value, and this gas is used for exhausting. If it flows into the vacuum pump, it will accelerate the deterioration of the oil used in the vacuum pump, and eventually cause the vacuum pump to malfunction, leading to a decrease in the reliability of the entire device. Therefore,
The present invention includes a reaction tube, a heating element surrounding the reaction tube, a gas supply section for supplying a reaction gas to the reaction tube, an exhaust pump for exhausting gas in one reaction tube, and a reaction tube and an exhaust pump. A main exhaust pipe that connects the main exhaust pipe, a valve to adjust the pressure of the reaction tube, a trap installed in the main exhaust pipe, an auxiliary exhaust pipe to gradually exhaust the gas in the reaction tube, and an auxiliary exhaust pipe. Reduced pressure CVD consisting of a return valve
In the equipment, a heat exchanger is installed in the auxiliary exhaust pipe to lower the temperature of the gas, and when the air inside the reaction tube after wafer loading passes through the auxiliary pipe and is exhausted, it exchanges heat and lowers the temperature. For example, the temperature of the air flowing into the exhaust vacuum pump is lower, which reduces the deterioration of the oil used in the vacuum pump, reduces vacuum pump failures, and improves the reliability of the pump and, ultimately, the reliability of the entire device. This is a technical measure that improves performance.

[Embodiments of the invention]

In the following, an embodiment of the present invention will be explained with reference to FIG. 2, in which the same parts as in FIG. 1 are given the same reference numerals and the explanation will be omitted. After opening the storage 5 and introducing the wafer 6 into the reaction tube 1, the exhaust valve 10 is closed, the auxiliary exhaust valve 11 is opened, and the air in the reaction tube 1 is slowly exhausted through the auxiliary exhaust pipe 9. At this time, the atmospheric pressure and high temperature air inside the reaction tube 1 undergoes heat exchange in the heat exchanger 16 provided in the auxiliary exhaust pipe 9, so the temperature becomes low, and the exhaust mechanical booster 14 and rotary pump It does not accelerate the deterioration of the oil used in the reaction tube 15, and when the pressure inside the reaction tube 1 becomes low to a certain extent, the auxiliary exhaust valve 11 is closed and the exhaust valve 10 is opened to exhaust the gas through the exhaust pipe 8. During the 0 reaction, exhaust is performed through the exhaust pipe 8, so that reaction products do not adhere to the heat exchanger 16 and reduce the efficiency of heat exchange.

〔Effect of the invention〕

According to the present invention, when high-temperature air at atmospheric pressure is slowly exhausted using an auxiliary exhaust pipe after being carried into a wafer reaction tube in a low-pressure CVD cycle, the temperature of the air is effectively controlled by a heat exchanger. This reduces the deterioration of the oil used in the exhaust vacuum pump, reducing the number of failures of the vacuum pump, improving its reliability, and ultimately improving the reliability of the entire device. can.

[Brief explanation of the drawing]

Figure 1 shows the conventional patch-type reduced pressure CVD! Configuration diagram of u[,
FIG. 2 is a block diagram of an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Reaction tube, 2... Heater, 3... Gas supply part, 4... Gas valve, 5... Storage, 6... Wafer,
7... Cooling trap, 8... Exhaust pipe, 9... Auxiliary exhaust pipe, 10... Exhaust valve, 11... Auxiliary exhaust valve, 12... Pressure gauge, 13... Leak valve ,1
4... Mechanical booster, 15... Rotary pump, 16... Heat exchanger. −),

Claims (1)

[Claims] A reaction tube, a heating element surrounding the reaction tube, a gas supply section for supplying reaction gas to the reaction tube, an exhaust pump for exhausting the gas in the reaction tube, and a book connecting the reaction and exhaust pumps. An exhaust pipe, a valve for adjusting the pressure of the reaction tube, a trap installed in the main exhaust pipe, an auxiliary exhaust pipe for gradually exhausting the gas in the reaction tube, and a valve for switching between the auxiliary exhaust pipes. 1. A low-pressure CVD apparatus comprising a valve and a low-pressure CVD apparatus, characterized in that an auxiliary exhaust pipe is provided with a heat exchanger for lowering the temperature of gas.