JP5504107B2 - Backflow prevention system and vacuum pump equipped with the backflow prevention system - Google Patents

Description

  The present invention relates to a backflow prevention system and a vacuum pump equipped with the backflow prevention system, and more particularly to a backflow prevention system that prevents backflow to the chamber due to the stoppage of the vacuum pump and is easy to recover, and the backflow prevention system. It is related with the vacuum pump provided with.

  In the manufacturing process of a semiconductor element, a CVD (Chemical Vapor Deposition) process, an etching process, and the like are performed using a chemical vapor reaction, and various gases are used in a process chamber. Recently, in this process chamber, hundreds of semiconductor wafers are often processed at a time.

The exhaust gas generated from the process chamber through a chemical vapor reaction or the like includes harmful P ₄ gases (perfluorocarbon: global warming gas) such as CF ₄ (Freon 14) and C ₄ F ₈ (Freon 318). It is. Since this PFC gas is extremely stable, it is harmful to the environment if it is released into the atmosphere without being decomposed.

  For this reason, as shown in FIG. 4, a vacuum pump 5 such as a turbo molecular pump or a dry pump is connected to the process chamber 1 in order to evacuate to a low pressure necessary to remove this harmful exhaust gas. .

A gate valve 3 is disposed in the pipe between the vacuum pump 5 and the process chamber 1. The harmful exhaust gas output from the vacuum pump 5 is sent to the abatement apparatus 7, and for example, PFC gas is decomposed into harmless CO ₂ and HF (hydrogen fluoride) by plasma. However, the abatement device 7 may be omitted.

  By the way, when foreign matter such as dust is mixed in the vacuum pump 5, an abnormal overload or over-torque state occurs and a pump stop signal is issued. At this time, a closing command is also transmitted to the gate valve 3, but the time required for stopping the pump and the time required for closing the gate valve 3 are close to each other. Depending on the situation, the gate valve 3 is delayed after the pump is stopped. It is also assumed that is closed.

  Specifically, it takes about 1 second from the start of closing of the gate valve 3 to the complete closing. On the other hand, since the emergency stop of the vacuum pump 5 is a setting that assumes an abnormal state of the pump, the setting of the motor current value and the like are often set in the limit region of the pump. The time from when the pump stop signal is issued to when the pump stops is usually about 1 second, although it depends on the contents of the pump abnormality.

  For this reason, if the gate valve 3 is closed after receiving the pump stop signal from the vacuum pump 5 side, the pump may stop before the gate valve 3 is completely closed.

  In this case, since the pressure in the process chamber 1 is reduced, the gas flows backward from the vacuum pump 5 side toward the process chamber 1. In this reverse flow, the dust adhering to the inside of the vacuum pump 5 or the piping is peeled off or the like and rides on the flow of the reverse flow gas and enters the process chamber 1. At this time, a large number of semiconductor wafers may be instantly contaminated and cause serious damage.

  In order to avoid such an adverse effect, when a failure factor occurs in the vacuum pump, a valve closing signal is first transmitted, and then the vacuum pump is forcibly continued until about 2 seconds before the vacuum pump is stopped. A method is disclosed (Patent Document 1).

JP 2006-66555 A

However, the method of Patent Document 1 is intended to forcibly continue the operation of the vacuum pump until the valve closing time is exceeded with sufficient margin in consideration of the valve closing time. For this reason, it is necessary to modify the pump control circuit. Further, forcibly continuing the operation of the vacuum pump even though it is an emergency abnormal situation that should be stopped immediately, may be undesirable for the vacuum pump and the entire system.
Another problem is system recovery work. Normally, the opening operation of the valve at the time of restoration is performed manually after releasing the valve closing signal from the viewpoint of safety. When the valve closing signal is a continuation signal, if the valve closing signal continues to be output from the device due to some abnormality, the valve cannot be opened, which hinders recovery. In addition, in order to release the valve closing signal, it was necessary to go to the device and release it.

  The present invention has been made in view of such conventional problems, and includes a backflow prevention system that prevents backflow to the chamber due to the stop of the vacuum pump and is easy to recover, and the backflow prevention system. An object is to provide a vacuum pump.

  Therefore, the present invention (Claim 1) is an invention of a backflow prevention system, which is configured independently of an automatic stop circuit of a vacuum pump, and dust or the like is put into a chamber through a valve when the vacuum pump is stopped. A backflow prevention system for preventing backflow, a current detection means for detecting a current value of a current at a predetermined location flowing in a vacuum pump, a current value detected by the current detection means, and a preset current setting value And a comparator that outputs a signal when the detected current value exceeds the current set value and determines that the vacuum pump is overloaded, and the valve is closed based on the output signal of the comparator. A valve closing means, and the current set value is smaller than an abnormal current value at which the emergency stop of the vacuum pump is performed, and is larger than a normal current value flowing through the vacuum pump, and The valve closing time required to completely close the valve after receiving the valve closing command should be within the time required for the emergency stop of the vacuum pump after the output signal of the comparator is issued. It is characterized by having been adjusted to.

  The current set value is smaller than the abnormal current value at which the emergency stop of the vacuum pump is performed and larger than the normal current value that normally flows through the vacuum pump, and is the value when the pump is in an overload state. Therefore, it is set at a time when there is a little margin before the pump emergency stop signal is issued, and the boundary region where the pump may be stopped as it is, or the operation may be continued without stopping the pump. It is within the range. It is desirable that a margin from the output of the comparator to the emergency stop signal of the pump being about 1 second or longer.

  The valve closing time is the time from when the valve closing command is received until this valve is completely closed. In the present invention, the valve closing command is not issued at the time of detection of an abnormal current value at which the emergency stop of the vacuum pump is performed, but is issued in an overload state of the vacuum pump a predetermined time before that time. Therefore, a certain amount of time can be secured until the vacuum pump is actually completely stopped. The time from when the output signal of the comparator is issued until the pump is actually stopped is preferably about 2 seconds or more.

  As described above, the vacuum pump can be stopped after the valve is completely closed, and dust and the like can be easily and efficiently prevented from flowing back into the chamber through the valve when the vacuum pump is stopped.

The present invention (Claim 2) is an invention of a backflow prevention system, characterized in that the output signal of the comparator is formed by a pulse signal that does not need to be released.
By forming the relay in a pulse shape without self-holding or the like, it is not necessary to release the output signal of the comparator when releasing the valve closing. Therefore, the operation can be easily performed with less labor.

  Furthermore, the present invention (Claim 3) is an invention of a vacuum pump, and comprises the backflow prevention system according to Claim 1 or Claim 2.

  As described above, according to the present invention (Claim 1), when the detected current value exceeds the current set value, the comparator determines that the vacuum pump is overloaded and outputs a signal. It has a valve closing means that closes the valve based on the output signal, and it is configured to generate a valve closing signal by catching the overload condition of the pump, so it can secure the time from the valve closing start to the vacuum pump stopping. It is possible to easily and efficiently prevent dust and the like from flowing back into the chamber through the valve when the vacuum pump is stopped. Since it can be configured only by remodeling the valve control circuit regardless of the vacuum pump, remodeling work can be easily minimized.

  Further, according to the present invention (claim 2), since the output signal of the comparator is formed by a pulse signal which does not need to be released, the overload state is temporary, and the vacuum is applied when it immediately converges. The pump can continue to operate without stopping. It is easy for the monitoring staff to confirm the operation of the vacuum pump and only give an instruction to open the valve. By issuing a pulse closing signal, the valve can be opened immediately when the operation of the vacuum pump is confirmed. Release of the valve closing signal is unnecessary and easy.

Overall system configuration diagram including a backflow prevention system according to an embodiment of the present invention Block diagram around the vacuum pump Timing chart Deposition system configuration diagram

Hereinafter, embodiments of the present invention will be described. An overall system configuration diagram of a backflow prevention system according to an embodiment of the present invention is shown in FIG. 1, and a block diagram around a vacuum pump is shown in FIG.
Note that the same components as those in FIG. 4 are denoted by the same reference numerals and description thereof is omitted. In FIG. 1, a process chamber 1 is a film forming apparatus, and a vacuum pump 5 is constituted by, for example, a dry pump.

  The vacuum pump 5 is supplied with power from, for example, 200 volts and a three-phase power source. This electric power is supplied to the motor circuit 15 through the control circuit 11 and the inverter circuit 13 inside the pump panel of the vacuum pump 5 through the main cable 9.

  The value of the current flowing through the inverter circuit 13 is constantly monitored and compared with a preset current setting value 19 by a comparator 17 built in the pump. The relay 21 is turned on when the monitored current value exceeds the current set value 19. The comparator 17 and the relay 21 that are included as standard equipment in the pump circuit may be used.

  On the other hand, a current monitor 23 is disposed on the main cable 9 of the power source so that the main current flowing through the main cable 9 is detected. The current detected by the current monitor 23 is compared with a preset current setting value 29 by a comparator 27. The relay 31 is turned on when the monitored current value exceeds the current set value 29.

  The relay 21 and the relay 31 are connected to the drive circuit of the gate valve 3 in an OR connection form. Therefore, the gate valve 3 is immediately closed when any one of the relays 21 and 31 operates.

  The control circuit of the backflow prevention system only closes the gate valve 3 and does not control until the vacuum pump 5 is stopped. The data logger 33 records the current trend detected by the current monitor 23, and the Max hold 35 holds the maximum value of the current detected by the current monitor 23. The data logger 33 and the Max hold 35 are tools for collecting reference data for setting the current setting value 19 and the current setting value 29, and can be omitted after the system is operated once. It is.

  The operation signal of the vacuum pump 5, the failure signal, and the closing signal of the gate valve 3 are transmitted to the process chamber 1 and can be displayed at the center. The gate valve 3 can be opened / closed at the center.

Next, the operation of the embodiment of the present invention will be described.
The control circuit of the backflow prevention system according to the embodiment of the present invention is configured independently of the control circuit of the vacuum pump 5. The stop control of the vacuum pump 5 is performed by a standard-equipped circuit built in the pump circuit as in the past, and the vacuum pump is immediately stopped when a current value abnormality or torque abnormality indicating an emergency state is detected. Is. When the vacuum pump is stopped, it is assumed that it usually takes about 1 second until the vacuum pump is completely stopped after the stop command is given due to the inertia of the rotor or the like.

  The current set value 19 and the current set value 29 are threshold values set lower than the current value indicating the emergency state of the vacuum pump and higher than the normal current value of the vacuum pump. Further, the gate valve 3 closing time (for example, 1 second) has a margin within the time from when the gate valve 3 is instructed to close from the current set value 19 or the current set value 29 to when the vacuum pump actually stops. These current setting values are experimentally determined locally so that they can be held.

  That is, these current set values are preferably detected as current values in an overload state occurring about 1 second or more before the timing at which the current value indicating the emergency state of the vacuum pump is detected. Therefore, for example, when the value of the abnormal current value of the vacuum pump is 15 A, the current set value is about 10 A, which is about twice the normal current value 5 A of the current monitor 23 detected by the data logger 33. In determining the magnitude of 10A, the peak value detected by the Max hold 35 is referred to.

When the current value detected by the current monitor 23 exceeds the current set value 29, or when the current value flowing through the inverter circuit 13 exceeds the current set value 19, a closing signal for the gate valve 3 is transmitted, and the gate Valve 3 is immediately closed. As described above, the closing time is approximately 1 second.
The reason why the comparator 17 and the comparator 27 are arranged is because it is assumed that which one can detect the overload state of the vacuum pump first depends on the operation situation, and only one of them may be arranged. Is possible.

Next, the sequence is processed as shown in the timing chart of FIG.
A foreign substance such as dust mixed in the vacuum pump may raise the value of the main current flowing through the main cable 9 or the current flowing through the inverter circuit 13 temporarily to cause an alarm. First, this case will be described.

  At this time, either the comparator 17 or the comparator 27 detects that the current value of the main current flowing through the main cable 9 or the current value flowing through the inverter circuit 13 is in a temporary overload state at timing t1. Then, the closing signal of the gate valve 3 is transmitted as a pulse for one second from t1 to t2, for example, and the gate valve 3 starts the closing operation from t1.

  The overload state at this time is temporary, and if it converges immediately, the vacuum pump 5 continues to operate without being stopped. However, since the gate valve 3 has been completely closed approximately 1 second after receiving the closing command as described above, after the monitoring person confirms that the operation of the vacuum pump 5 is safely continued in the center, At t3, an opening command for the gate valve 3 is transmitted.

  Conventionally, when the vacuum pump 5 is stopped in this manner, a monitor in a dust-free second floor center where the process chamber 1 is installed moves to the lower floor where the vacuum pump 5 is located. The operation of the vacuum pump 5 was resumed. At this time, it was necessary to take off the dust-proof suit and wear it again, which was a laborious work. However, by configuring the backflow prevention system as in the present embodiment, the supervisor can check the operation of the vacuum pump 5 while staying in the center, and then simply give an instruction to open the gate valve 3, so that it is easy. It is.

  On the other hand, although the overload state is detected at t4, this state does not stop temporarily, but when the abnormal current value which is an emergency state of the vacuum pump 5 is finally reached, the vacuum pump 5 is stopped at t6. A command is issued and the vacuum pump 5 is automatically stopped. This stop command is issued according to a stop circuit built in advance on the vacuum pump 5 side in a manner independent of the backflow prevention system of the present embodiment. That is, the abnormal current value is also uniquely set on the vacuum pump 5 side.

In this case, the monitoring staff checks the site because the situation is an emergency when the vacuum pump 5 is stopped.
As described above, the instruction signal for the gate valve 3 can be configured simply because it outputs only the closing signal while the valve is manually opened. In addition, when the operation of the vacuum pump 5 is confirmed, the operation of opening the gate valve 3 can be performed immediately by issuing a closing signal for the gate valve 3 in a pulsed manner. For this reason, it is not necessary to release the closing signal, which is easy.

DESCRIPTION OF SYMBOLS 1 Process chamber 3 Gate valve 5 Vacuum pump 7 Detoxifying device 9 Main cable 11 Control system circuit 13 Inverter circuit 15 Motor circuit 17, 27 Comparator 19, 29 Current setting value 21, 31 Relay 23 Current monitor 33 Data logger 35 Max hold

Claims (3)

A backflow prevention system that is configured independently of an automatic stop circuit of a vacuum pump and that prevents dust and the like from flowing back into the chamber through a valve when the vacuum pump is stopped,
Current detection means for detecting a current value of a current at a predetermined location flowing through the vacuum pump;
The current value detected by the current detection means is compared with a preset current setting value, and when the detected current value exceeds the current setting value, it is determined that the vacuum pump is overloaded and a signal A comparator that outputs
Valve closing means for closing the valve based on the output signal of the comparator,
The current set value is smaller than an abnormal current value at which the emergency stop of the vacuum pump is performed, and is larger than a normal current value flowing through the vacuum pump,
In addition, the valve closing time required to completely close the valve after receiving the valve closing command is within the time required from the time when the output signal of the comparator is issued until the emergency stop of the vacuum pump. Backflow prevention system characterized by being adjusted to fit.   2. The backflow prevention system according to claim 1, wherein the output signal of the comparator is a pulse signal that does not need to be released.   A vacuum pump comprising the backflow prevention system according to claim 1 or 2.

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