JPH07300393A - Roughing line venting mechanism - Google Patents

Abstract

PURPOSE:To provide a roughing line venting mechanism by placing an NO solenoid valve opening in power-off state, a buffer tank and an NC solenoid valve closing in power-off state in a roughing line connecting a rotary pump and an N2 source. CONSTITUTION:A treating chamber 9, a foreline valve 6 and a main valve 8 are closed and a rotary pump(RP) 1 is energized to evacuate a roughing line 2 and effect the roughing of the treating chamber 9 through a by-pass line. The valve 6 is opened, the operation of a main evacuation pump 7 such as a turbo-molecular pump is started and the valve 8 is opened to evacuate the treating chamber 9 in high vacuum. In the above process, an NO solenoid valve 12 is closed an NC solenoid valve 13 is opened and pressurized N2 gas is introduced from an N2 source 4 into a buffer tank 11. In the case of power failure, the valve 6 and other valves are closed to protect the pump 7 and the treating chamber 9 from the intrusion of air. When the NC solenoid valve 13 is closed and the NO solenoid valve 12 is opened, the N2 gas in the tank 11 is flowed into a easing RP1 and a piping 2 to reduce the pressure to atmospheric pressure and reduce the load on the pump in start-up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a vacuum exhaust system in a semiconductor device manufacturing apparatus and other vacuum devices. In particular, it relates to a mechanism that can effectively vent nitrogen in the roughing line when a power failure occurs. As the semiconductor device manufacturing apparatus, there are an etching apparatus, a CVD apparatus, an epitaxial apparatus, a vapor deposition apparatus, a sputtering apparatus and the like. In addition to this, various vacuum devices such as an ion beam implantation device and an electron beam irradiation device are used in various industrial fields. Since these devices always perform processing in vacuum, the processing chamber and processing space are evacuated.

In the case of an apparatus for drawing a high vacuum, it is carried out in two steps, rough drawing and main drawing. Roughing is done with a rotary pump. This physically exhausts gas by rotating an eccentric rotor in a cylindrical casing having a discharge (exhaust) port and a suction port.

The rotor has a vane that advances and retracts in the radial direction, and the tip of the vane contacts the inner wall of the casing. Base
Since the volume of the space formed by the rotor, the rotor, and the inner wall of the casing changes, the gas can be sucked and compressed on the high pressure side and exhausted to the low pressure side. 1 quickly by rotary pump
The pressure is reduced to 0 ^-5 to 10 ^-6 Torr, and then the main rotation is performed while continuing the operation of the rotary pump. Various pumps such as an oil diffusion pump, a turbo molecular pump, a titanium sublimation pump, and a cryopump are used as the exhaust system of the main draw.

The rotary pump continues to run while the vacuum system is evacuated. When opening the vacuum system, the valve in between may be placed closed and the rotary pump may be left running. The operation of the rotary pump itself may be stopped. In this case, if the suction side has a low pressure, the oil may flow back to the suction side. Therefore,
At the same time as stopping the rotary pump, nitrogen at atmospheric pressure is also introduced into the suction side. Oil backflow can be suppressed by balancing the pressure.

The operation of introducing nitrogen at atmospheric pressure to the suction side when the rotary pump is stopped in this way is called nitrogen venting. It is called a roughing line that includes the rotary pump and the piping connected to the main pumping equipment. Since nitrogen gas is introduced into this system, it is referred to as a nitrogen vent of the roughing line here.

[0006]

2. Description of the Related Art A nitrogen venting mechanism of a roughing line according to a conventional example will be described with reference to FIG. Rotary pump 1
Is connected to a NO solenoid valve 3 via a roughing pipe 2, which is connected to a nitrogen source 4 via a nitrogen pipe 5. The nitrogen source 4 may be an individual nitrogen gas cylinder, or may be a common nitrogen line supplied to each part of the factory. The NO solenoid valve 3 is written as a normal open. This is a valve that has a common power source with the pump, is open when the pump power source is off, and closes only when the pump power source is switched on. Of course, it can be opened when the power is on. However, it always opens when there is a power failure.

The roughing piping 2 is connected to a turbo molecular pump 7 via a foreline valve 6. This reaches the processing chamber 9 via the main valve 8. The main pump is not limited to the turbo molecular pump, and the above-mentioned pump can be used. The processing chamber is a vacuum space for performing various processes such as vapor deposition, sputtering, ion beam generation, CVD, etching and the like. Roughing line means
Tally pump 1, roughing piping 2, solenoid valve 3, nitrogen piping 5
Means It is the rotary pump and the roughing piping 2 that vent the nitrogen.

When drawing a vacuum, the procedure is as follows. The main valve 8 and the far line valve 6 are closed. The solenoid valve 3 is open. The processing chamber 9 is closed. Driving of the rotary pump 1 is started. A signal is transmitted through the signal line 10, and at the same time, the NO solenoid valve 3 is closed. Since the roughing piping 2 becomes a vacuum, the foreline valve 6 is opened. The main pump 7 is started. You can draw a vacuum up to this part. Then open the main valve 8. The processing chamber 9 gradually becomes a vacuum. After reaching an appropriate degree of vacuum, desired treatment is performed.

When the vacuum exhaust is stopped, the procedure is as follows. The main valve 8 is closed. The main pump 7 is stopped. Close the foreline valve 6. The piping including the pump 7 is maintained in vacuum. The rotary pump 1 is stopped. At the same time, the NO solenoid valve 3 opens. Pressurized nitrogen gas flows in from the nitrogen source 4 and pressurizes the suction side of the rotary pump. Since the electromagnetic valve 3 and the pump 1 share the power source in this manner, nitrogen can be vented immediately when the pump is stopped.

[0010]

[Problems to be Solved by the Invention] There is no problem in normal operation and stop. However, problems occur when there is a power outage during operation. The probability of power failure during operation is low, but it cannot be said. Suppose a sudden power failure occurs when the rotor rotates and continues vacuuming. A vacuum is maintained in the processing chamber 9 by automatically closing a main valve and other valves.

The processing chamber is fine, but the roughing line presents a problem. Since the rotor stops and the NO solenoid valve 3 opens, nitrogen gas flows from the nitrogen source to the roughing line. This is done instantly. Since the exhaust gas from the processing chamber was passed through the roughing pipe, it often contains toxic gas and dangerous gas. Such dangerous gas and toxic gas flow into the nitrogen source 4 and the nitrogen pipe 5 through the opened solenoid valve 3. This is done in an instant. Therefore, the nitrogen source is polluted. With a common nitrogen source, other devices can also be contaminated with hazardous toxic gases through it.

There is another problem. The nitrogen source 4 is pressurized to some extent rather than atmospheric pressure. If it is not pressurized, nitrogen cannot be distributed to each part. So for example 1
It is assumed that the pressure is up to ² kg / cm ² (based on the atmospheric pressure). This pressure is applied to the suction side of the pump during a power failure. Since the pressure on the atmosphere side is 0 (because the atmosphere is the reference), the pressure on the suction side becomes abnormally high.

When the rotary pump starts moving again after the power failure is released, the suction side of the pump is 1 to ² kg / cm ^2.
Since the pressure is applied and no pressure is applied to the exhaust side, the pump operation becomes abnormal. The rotary pump is designed to operate when both the suction side and the exhaust side are at atmospheric pressure. It is not desirable to operate when the suction side is under pressure. Pressurized operation is not expected in rotary pumps. Driving from pressurization may increase the load and cause the pump to beat.

The volume that must be sucked in under pressure is the internal space of the roughing pipe 2. This part uses thick piping to increase the conductance. Therefore, the volume of roughing piping is quite large. Pumping a large volume from the pressurized state is a burden on the pump. Therefore, we would like to start operation under atmospheric pressure instead of starting operation after pressurization even after a power failure. The present invention seeks to solve the above two problems that occur during a power failure. That is, it is an object of the present invention to propose a mechanism in which a dangerous gas and a toxic gas in the exhaust system of the processing chamber do not enter the nitrogen line at the time of power failure and the pump starts to move from the atmospheric pressure at the time of restart.

[0015]

The roughing line nitrogen venting mechanism of the present invention includes a valve (NO valve), a buffer tank, which is opened when the power is turned off, in a roughing piping connecting a rotary pump and a nitrogen source. A valve (NC valve) that is closed when the power is turned off is provided. The buffer tank is connected to the nitrogen source by the NC valve. The buffer tank is connected to the rotary pump by an NO valve. Alternatively, the intermediate buffer tank may be omitted and replaced by a pipe having a proper volume, a twisting tube, or the like.

[0016]

[Function] During normal operation, the NO solenoid valve is closed and N
C Solenoid valve is open. The buffer tank is connected to the nitrogen source. The pressure in the buffer tank is equal to the pressure in the nitrogen source P. As described above, P has a gauge pressure of about 1 to 2 atm. The pressure is lower on the pump side than the NO solenoid valve. Suppose there is a sudden power outage here. The intermediate valve such as the main valve is closed, and the processing chamber and the high vacuum pump are separated from the rotary pump. The NC solenoid valve is closed to disconnect the nitrogen source and the buffer tank. On the contrary, since the NO solenoid valve is opened, nitrogen in the buffer tank is introduced into the roughing pipe having a low pressure and is vented to the atmospheric pressure.

Since the nitrogen gas existing in the buffer tank at the pressure P of the nitrogen source spreads to the roughing pipe, the pressure drops. The volume ratio between the pipe and the buffer tank is determined so that this pressure is about atmospheric pressure. Then, at the time of power failure, the pressure on the suction side of the rotary pump is always atmospheric pressure. When the power failure is repaired, electricity is turned on, and the rotary pump is rotated again, suction is started from atmospheric pressure, so the pump is not burdened. The gas in the pump space can be smoothly sucked.

Furthermore, since the NC solenoid valve is inserted in the pipe between the nitrogen source and the rotary pump, the roughing pipe and the nitrogen source are not connected when a power failure occurs. Therefore, the harmful gas and the dangerous gas emitted from the processing chamber do not move to the nitrogen source. NO
Since the solenoid valve and the NC solenoid valve are opened and closed complementarily, the nitrogen source and the rotary pump are not directly connected. Assuming that the volume of the roughing pipe is W, the volume of the buffer tank is V, the pressure of the nitrogen source is P, and the pressure on the suction side during operation of the rotary pump is Q, the buffer tank and the rotary tank are in a power failure. When the pumps are connected and both are disconnected from the nitrogen source, the pressure R in the roughing line is

R = (PV + QW) / (V + W) (1)

Is given by P is predetermined as a unique value of the nitrogen source. The volume of the roughing pipe W is also predetermined. In many cases, Q = -1 kg / cm ² . Then, by applying the desired pressure R, the desired volume V of the buffer tank can be calculated.

V = (R−Q) W / (P−R) (2)

For example, if P = 1.5 kg / cm ² ,
If you want to set R = 0 (atmospheric pressure), Q = -1kg / cm
^{As 2} , the relationship of V = 2W / 3 is obtained. By giving the volume of the buffer tank in this way, the pressure on the suction side of the rotary pump can be made atmospheric pressure at the time of power failure. The pressure is not limited to atmospheric pressure, and may be slightly lower than atmospheric pressure. It can also be greater than atmospheric pressure. This can be set arbitrarily according to the buffer tank volume.

Further, by attaching a pressure adjusting valve to the buffer tank, the pressure of the gas flowing out of the tank can be reduced and the tank capacity can be made smaller. A coiled tube may be provided in addition to the Bach tank. In this case, even if the inner diameter of the tube is small, a large volume can be obtained by winding it many times.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A roughing line vent mechanism according to an embodiment of the present invention will be described with reference to FIG. The roughing pipe 2 is connected to the suction port of the rotary pump 1. This goes through the foreline valve 6 and the turbo molecular pump 7 which is the main pump.
Connected to. The pump 7 is connected to the processing chamber 9 via a main valve 8. The roughing pipe 2 is further connected to a normally open solenoid valve (NO). The solenoid valve 12 is connected to a normally closed (NC) solenoid valve 13 via an intermediate pipe 15.

The intermediate pipe 15 is provided with a buffer tank 11 having an appropriate volume. The solenoid valve 13 is connected to the nitrogen source 4 via the nitrogen pipe 5. Since the solenoid valves 12 and 13 are opened and closed in synchronization with the operation of the rotary pump 1, the signal line 1
0 and 16 are provided between the two. When the processing chamber is open to the atmosphere and the rotary pump is stopped, the NO solenoid valve 1
2 is open and NC solenoid valve 13 is closed. The suction side of the rotary pump is at atmospheric pressure. The valves 6 and 8 are also open. The processing chamber is also at atmospheric pressure.

To start the process, the following is done.
Close the processing chamber (close the leak valve, etc.). The valves 6 and 8 are closed. The rotary pump 1 is operated. The roughing pipe 2 becomes a vacuum. There is a bypass path (not shown), and the rotary chamber pumps the processing chamber roughly. Open the foreline valve 6. The main draw pump is also evacuated. Start operation of the main draw pump. The main valve 8 is opened and the processing chamber 9 is pulled out. At this time, the NO solenoid valve 12 is closed and the NC solenoid valve 13 is open. The buffer tank 11 is filled with pressurized nitrogen from the nitrogen source 4. The pressure of the nitrogen source is such that P is 1 to 2 atm. At this time, the pressure in the buffer tank is also P. The suction side of the rotary pump 1 is -1 atm (gauge pressure).

It is assumed that a power outage occurs here. When the foreline valve and other valves are closed, the pump 7 and the processing chamber 9
Are protected from the ingress of the atmosphere. The NC solenoid valve remote from the rotary pump 1 is closed. The near NO solenoid valve opens. Nitrogen in the buffer tank 11 spreads to the casing of the rotary pump 1 and the roughing pipe 2. The spread reduces the pressure. The reduced pressure is set to almost atmospheric pressure. Therefore, pressurized nitrogen is not applied to the suction side of the rotary pump. Since the rotary pump is started up from atmospheric pressure, the load on the pump is reduced.

Furthermore, a newly added NC solenoid valve 1
For 3, the nitrogen source and the roughing piping are cut off from each other. Exhaust gas from the processing chamber does not mix with the nitrogen source. The nitrogen source is never contaminated with hazardous or poisonous gas. Improves safety. FIG. 3 is a diagram showing another embodiment. The tube 17 is used instead of the tank. If the cross-sectional area is A and the length is L, this volume V is V =
Given by AL. Even if the cross-sectional area A is small,
If the length L is set large, the volume can be increased. A sufficient volume can be obtained by winding a large number of tubes in a coil. Furthermore, in FIG. 1, by providing a pressure adjusting valve in the buffer tank, it is possible to reduce the pressure when nitrogen flows out from the tank during a power failure.

[0029]

INDUSTRIAL APPLICABILITY The present invention provides a valve between a rotary pump and a nitrogen source in a rough evacuation line of a vacuum exhaust system, a valve that opens when the power is turned off, a buffer tank or a tube, and a valve that closes when the power is turned off. Has been installed. Therefore, in the event of a power failure, the valve that closes when the power is off can prevent dangerous gas on the processing device side from entering the nitrogen source. In addition, since the buffer tank or tube communicates with the rotary pump by the valve that opens when the power is turned off, the tank,
The pressurized nitrogen in the tube spreads and the pressure on the suction side of the rotary pump can be made to be about atmospheric pressure. Therefore, at the next start, the rotary pump can start vacuuming from atmospheric pressure.

[Brief description of drawings]

FIG. 1 is a schematic system diagram of a roughing line vent mechanism according to an embodiment of the present invention.

FIG. 2 is a schematic system diagram of a roughing line vent mechanism according to a conventional example.

FIG. 3 is a schematic view showing the buffer tank of FIG. 1 replaced by a tube.

[Explanation of symbols]

 1 Rotary Pump 2 Roughing Piping 3 NO Solenoid Valve 4 Nitrogen Source 5 Nitrogen Piping 6 Foreline Valve 7 Tarbo Molecular Pump 8 Main Valve 9 Processing Chamber 10 Signal Line 11 Buffer Tank 12 Normal Open Solenoid Valve 13 NORMAL CROSS solenoid valve 15 Intermediate piping 16 Signal line 17 Tube

Claims (2)

[Claims] 1. An apparatus for vacuuming a processing chamber by using a roughing vacuum pump and a main vacuuming pump together to perform processing by utilizing a vacuum, a rotary pump for roughly vacuuming the processing chamber, and a pump when the pump is stopped. The nitrogen source that should supply pressurized nitrogen gas to the rotary pump and the roughing piping and the roughing piping connected to the rotary pump are connected and open when the power is off.
O solenoid valve, buffer tank connected to NO solenoid valve,
It includes an NC solenoid valve that connects the buffer tank and a nitrogen source and closes when the power is off. During a power failure, the nitrogen in the buffer tank spreads to the roughing piping and the suction side of the rotary pump, A roughing line vent mechanism characterized in that the pressure is set to be almost equal to the atmospheric pressure. 2. An apparatus for vacuuming a processing chamber by using a roughing pump and a main pump together to perform processing by utilizing a vacuum, a rotary pump for roughing the processing chamber, and a pump when the pump is stopped. The nitrogen source that should supply pressurized nitrogen gas to the rotary pump and the roughing piping and the roughing piping connected to the rotary pump are connected and open when the power is off.
A tube connected to the O solenoid valve and the NO solenoid valve, and a tube
Tube connected to a nitrogen source and closed when the power is off, including an NC solenoid valve. When a power failure occurs, the nitrogen in the tube spreads to the roughing piping and the suction side of the rotary pump, A roughing line vent mechanism characterized in that the pressure is set to be almost equal to the atmospheric pressure.