JPH0517287A - Discharging method and device for reaction tube for semiconductor wafer treatment - Google Patents

Abstract

PURPOSE:To provide the discharge method and device for a reaction tube for a semiconductor wafer treatment which is constituted to allow the evacuation of the inside of the reaction tube to a prescribed vacuum degree in a relatively short period of time while ingeniously averting a pressure shock to be the cause for particle splashing in a discharge process even if some particles exist in the reaction tube. CONSTITUTION:The discharge device is constituted of a discharge pipeline 3 which is installed between the reaction tube 1 and a discharge pump 2, a main valve 4 which is connected to the mid-way of the discharge pipeline, a bypass pipeline 5 which has a bypass valve 6 bypassing this main valve, and an inert gas source 12 for regulating a discharge capacity which is branched and connected via a flow rate controller to the discharge pipeline between the above-mentioned main valve and the discharge pump. The gas for regulating the discharge capacity is introduced to the suction side of the discharge pump before the main valve of the discharge pipeline is opened in the initial stage after the start of the discharge. In addition, the inside of the reaction tube is evacuated until the pressure therein attains the prescribed ultimate vacuum degree while the amt. of the gas to be introduced is gradually decreased down to zero after the main valve is opened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for exhausting a reaction tube used in process steps such as oxide film formation and doping of semiconductor wafers.

[0002]

2. Description of the Related Art First, a conventional exhaust device for a reaction tube and an exhaust method will be described with reference to FIG. In the figure, 1 is a reaction tube, 2 is an exhaust pump (for example, a rotary vacuum pump), 3 is an exhaust pipe line connecting the reaction pipe 1 and the exhaust pump 2, 4 is a main valve connected to the exhaust pipe line 3, 5 is the main valve 4
Is a bypass pipe, and 6 is a bypass valve connected to the bypass pipe 5. Further, as the bypass pipe line 5, a pipe (about 1/5) which is sufficiently thinner than the pipe diameter of the exhaust pipe line 1 is used. In addition, 7 is a semiconductor wafer, and 8 is a boat used when inserting the semiconductor wafer 7 into the reaction tube 1.

Next, prior to the process treatment of the semiconductor wafer 7, a method of exhausting the reaction tube 1 using the exhaust device will be described. In the initial stage of exhaust, the main valve 4 is closed and the bypass valve 6 is opened. Start the exhaust pump 2 in the state of
Vacuuming is performed while narrowing the exhaust passage through the bypass pipe 5 having a small pipe diameter until the degree of vacuum in the reaction pipe decreases to about 1 mbar. Next, the main valve 4 is opened, and the reaction tube 1 is evacuated until the degree of vacuum reaches about 10 ^-2 mbar.

[0004]

By the way, in the conventional exhaust method described above, the following problems occur in the exhaust process. That is, in the initial stage of exhaust, the bypass pipe 5 having a small diameter is
When the main valve 4 of the exhaust pipe line 3 is opened after exhausting to a certain degree of vacuum through, the internal pressure of the reaction tube 1 sharply decreases from the state immediately before opening the main valve (the exhaust pump operates with a constant exhaust capacity. Therefore, due to the shock of this sudden pressure change, particles adhering to the inner wall surface of the reaction tube scatter and fly up, and onto the surface of the unprocessed semiconductor wafer housed in the reaction tube. It becomes attached. Moreover, if particles adhere to the semiconductor wafer, the yield of products will be adversely affected.

Therefore, conventionally, as a measure for preventing the scattering of particles, the reaction tube is frequently washed and used in a clean state with few residual particles. Furthermore, when the reaction tube is evacuated, the main valve is opened after evacuating to a vacuum degree as high as possible through the bypass conduit, and the pressure shock accompanying switching of the valve is alleviated. However, frequent cleaning of the reaction tube in a short cycle requires a lot of time and labor for maintenance work and causes a decrease in the operating rate of the process equipment. Further, exhausting to a high degree of vacuum through a bypass pipe having a small pipe diameter causes a prolongation of the cycle time of wafer process processing and a decrease in throughput of process processing steps.

The present invention has been made in view of the above points, and an object thereof is to skillfully avoid a pressure shock that causes particle scattering in the exhaust process even when a certain amount of particles exist in the reaction tube. An object of the present invention is to provide a method and an apparatus for evacuating a reaction tube capable of evacuating to a predetermined vacuum degree in a relatively short time.

[0007]

According to the present invention, the above-mentioned object is to introduce the exhaust capacity adjusting gas into the intake side of the exhaust pump before opening the main valve of the exhaust pipe in the initial stage after the start of exhaust, and After the main valve is opened, the amount of gas introduced is gradually reduced to zero while vacuuming is performed until the pressure in the reaction tube reaches a predetermined ultimate vacuum. Further, as the exhaust capacity adjusting gas used here, an inert gas such as nitrogen gas is used.

On the other hand, the exhaust system of the present invention used for carrying out the above-described exhaust method comprises an exhaust pipe line provided between a reaction pipe and an exhaust pump, a main valve connected in the middle of the exhaust pipe line, It is composed of a bypass pipe with a bypass valve that bypasses the main valve, and a gas source for exhaust capacity adjustment that is branched and connected to the exhaust pipe between the main valve and the exhaust pump via a flow controller.

[0009]

As described above, by opening the main valve while introducing gas from the outside into the intake side of the exhaust pump during the exhaust process, part of the exhaust capacity of the exhaust pump is exhausted from the adjusting gas introduced from outside. Since it is spent, the effective exhaust capacity acting on the reaction tube is reduced by that much, and the rapid pressure change of the reaction tube due to the opening of the main valve is alleviated. Further, by gradually reducing the gas introduction amount from here to zero, the degree of vacuum in the reaction tube continuously rises and finally reaches a predetermined degree of vacuum without shock. Thereby, scattering of particles in the reaction tube is avoided. In addition, the introduction amount of the exhaust gas for adjusting the exhaust capacity and its reduction rate should be set to the optimum conditions in consideration of the ultimate vacuum in the reaction tube before opening the main valve, the exhaust capacity of the exhaust pump to be used, and the rising speed of the vacuum. Shall be set.

[0010]

FIG. 1 shows an exhaust device for a reaction tube according to an embodiment of the present invention. In addition to the structure shown in FIG. The pipe 9 is branched, and the gas introduction pipe 9 is connected to an inert gas source 12 such as nitrogen gas as an exhaust gas adjusting gas through a flow controller 10 and an opening / closing valve 11.

The reaction tube 1 employing the exhaust device having such a configuration
In order to evacuate the exhaust gas, first, in the initial stage of evacuation, the reaction pipe 1 reaches a certain degree of vacuum by the exhaust pump 2 through the bypass pipe line 5 of the exhaust pipe line 3 with the main valve 4 closed, as in the conventional method. Evacuate to. Next, the valve 1 of the gas introduction line 9
1 is opened, and an inert gas is introduced from the gas source 12 to the intake side of the exhaust pump 2 so as to balance the degree of vacuum in the reaction tube 1 at that time and the exhaust capacity of the exhaust pump 2, and then exhausted in this state. The main valve 4 of the line 3 is opened. Subsequently, the gas introduction amount is gradually reduced to zero by the control of the flow rate controller 10, and the reaction tube 1 is finally evacuated until a predetermined degree of vacuum is reached.

[0012]

As described above, according to the exhaust method of the present invention, during the exhaust process from the initial stage after the start of exhaust until the predetermined vacuum level is reached, the vacuum level in the reaction tube does not suddenly change. It will continue to rise. Therefore, it is possible to avoid such a problem that particles remaining in the reaction tube fly up and adhere to the unprocessed semiconductor wafer housed in the reaction tube, thereby improving the product yield. Moreover, since particles can be prevented from scattering during the exhaust process, frequent cleaning of the reaction tube is not required, and the operating rate of the process processing apparatus is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an exhaust device for a reaction tube according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional reaction tube exhaust device.

[Explanation of symbols]

1 reaction tube 2 exhaust pump 3 exhaust pipe 4 main valve 5 Bypass pipeline 6 Bypass valve 7 Semiconductor wafer 9 gas introduction line 10 Flow controller 12 Inert gas source

Claims (3)

[Claims] 1. A method of evacuating a reaction tube for accommodating a semiconductor wafer and performing a process, wherein a vacuum is drawn inside the reaction tube through an exhaust pump, wherein a main valve of an exhaust pipe line is provided at an initial stage after the start of evacuation. Introduce a gas for adjusting the exhaust capacity to the intake side of the exhaust pump before opening the valve, and gradually decrease the gas introduction amount to zero after opening the main valve until the pressure in the reaction tube reaches the specified ultimate vacuum. A method for evacuating a reaction tube for semiconductor wafer processing, characterized by evacuation. 2. The exhaust method according to claim 1, wherein the exhaust capacity adjusting gas is an inert gas. 3. An exhaust pipe line provided between a reaction pipe and an exhaust pump, a main valve connected in the middle of the exhaust pipe line, a bypass pipe line with a bypass valve bypassing the main valve, and the main valve. And a gas source for adjusting exhaust capacity, which is branched and connected to an exhaust pipe via a flow controller between the exhaust pump and the exhaust pump.
An exhaust device for a reaction tube for processing a semiconductor wafer, which is used for carrying out the exhaust method described above.