JP2000161236A - Vacuum pressure control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum pressure control system which prevents the excessive variation to an object vacuum pressure value, when the vacuum pressure in a vacuum container is changed by controlling the opening of a vacuum proportional switching valve by making the valve opening instruction value immediately after the starting of movement of the valve plug of the vacuum proportional switching valve as the lowest point of the valve opening instruction value, and to provide a vacuum pressure control system which corrects the slippage of the correspondent relation of the opening of the vacuum proportional switching valve, and the valve opening instruction value. SOLUTION: A valve opening instruction value corresponding to the output value of a potentiometer when a poppet valve plug is contacted closely with a valve seat is found as a tentative valve opening instruction, at S3, and the zero point of the opening of the new vacuum proportional switching valve decided at S11 is made as a valve opening instruction value varied a little from the tentative valve opening instruction value. Since the zero point of the opening of the new vacuum proportional switching value decided at S11 is a value a little lower than the decided value, it is made as the valve opening instruction value immediately after the starting of movement of the poppet valve plug.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a vacuum pressure control system used in a semiconductor manufacturing apparatus.

[0002]

2. Description of the Related Art Conventionally, for example, CVD of a semiconductor manufacturing apparatus
In the apparatus, a material gas composed of an element constituting a thin film material is supplied onto a wafer while keeping a reaction chamber in a reduced pressure state, that is, a vacuum state. For example, FIG.
In the CVD apparatus shown in FIG.
The material gas is supplied from the inlet 11 of the reaction chamber 10 to the wafer in the chamber 0 and exhausted by the vacuum pump 13 from the outlet 12 of the reaction chamber 10 to maintain the inside of the reaction chamber 10 in a vacuum state.

At this time, it is necessary to keep the vacuum pressure in the reaction chamber 10 constant. The constant value varies depending on various conditions, and ranges from the atmospheric pressure or a low vacuum close to the atmospheric pressure to a high vacuum. Cross over. In view of this, the present applicant has disclosed in Japanese Patent Publication No. 2677536 a vacuum pressure control system capable of accurately maintaining a constant vacuum pressure over a wide range from low vacuum close to atmospheric pressure to high vacuum.

[0004] An outline of a vacuum pressure control system (hereinafter, referred to as "prior art vacuum pressure control system") described in Japanese Patent Publication No. 2677536 will be briefly described. FIG. 15 shows a block diagram of a conventional vacuum pressure control system with respect to FIG. The prior art vacuum pressure control system comprises a controller 20, an air pressure controller 3
0, the vacuum proportional on-off valve 16 as the operation unit 40, and the detection unit 60
, And vacuum pressure sensors 14 and 15.

The controller 20 includes an interface circuit 21, a vacuum pressure control circuit 22, and a sequence control circuit 2.
Consists of three. The interface circuit 21 sends a signal from a field input via a button on the front panel of the controller 20 and a signal from a remote input via a connector on the back panel of the controller 20 to the vacuum pressure control circuit 22, the sequence control circuit 23, and the like. It converts it into a suitable signal.

The vacuum pressure control circuit 22 performs PID feedback control on the vacuum pressure in the reaction chamber 10 shown in FIG.
This is a circuit to be controlled. Sequence control circuit 23
Is a circuit that causes the drive coil SV1 of the first solenoid valve 34 and the drive coil SV2 of the second solenoid valve 35 in the air pressure control unit 30 to perform a predetermined operation in accordance with the operation mode given from the interface circuit 21. It is.

The air pressure control unit 30 includes a position control circuit 31,
It comprises a pulse drive circuit 32, a time opening / closing operation valve 33, a first solenoid valve 34, and a second solenoid valve 35. Position control circuit 31
Is supplied via an amplifier 19 from a valve opening command value given from the vacuum pressure control circuit 22 and a potentiometer 18 (corresponding to a “valve opening sensor”) provided on the vacuum proportional on-off valve 16. The position of the vacuum proportional on-off valve 16 is controlled by comparing the opening degree of the vacuum proportional on-off valve 16. The pulse drive circuit 32 includes the position control circuit 3
A pulse signal is transmitted to the time opening / closing operation valve 33 based on the control signal from the control unit 1.

The time opening / closing operation valve 33 incorporates a supply side proportional valve and an exhaust side proportional valve (not shown), and according to a pulse signal from a pulse drive circuit 32, the supply side proportional valve and the exhaust side proportional valve. The proportional valve is operated to open and close over time, and the air pressure in the pneumatic cylinder 41 of the vacuum proportional on-off valve 16 (see FIGS. 13 and 14 described later) is adjusted via the first solenoid valve 34.

[0009] The vacuum proportional on-off valve 16, which is the operation unit 40,
Referring to FIG. 16, the vacuum pump 13
To change the conductance of the exhaust system. 13 and 14 show cross sections of the vacuum proportional on-off valve 16. As shown in the figure, the center of the piston rod 4
3 are provided. Then, the pneumatic cylinder 4 above the vacuum proportional on-off valve 16 is
1, a piston 44 is fixed, and a poppet valve body 45 is fixed in a bellows type poppet valve 42, which is a lower portion of the vacuum proportional on-off valve 16. Therefore, the poppet valve body 45 can be moved by the pneumatic cylinder 41.

In this vacuum proportional on-off valve 16, compressed air is not supplied into the pneumatic cylinder 41 through the supply port 18A, and when the inside of the pneumatic cylinder 41 communicates with the exhaust line through the exhaust port 18B, the pneumatic cylinder 41
The downward biasing force of the return spring 46 inside the piston 44
Therefore, as shown in FIG.
The O-ring 50 (corresponding to an “elastic sealing member”) provided on the valve 5 is in close contact with the valve seat 47, and the vacuum proportional on-off valve 16 is shut off.

On the other hand, when compressed air is supplied into the pneumatic cylinder 41 via the air supply port 18A, a downward biasing force of the return spring 46 in the pneumatic cylinder 41
Since the upward pressure of the compressed air in the pneumatic cylinder 41 simultaneously acts on the piston 44, the poppet valve body 45 is separated from the valve seat 47 as shown in FIG. 16 is open.

Accordingly, the distance at which the poppet valve element 45 is separated from the valve seat 47 can be controlled by supplying and exhausting compressed air to the pneumatic cylinder 41 as a valve lift. The distance that the poppet valve element 45 separates from the valve seat 47 is measured by the potentiometer 18 via a slide lever 48 connected to the piston 44 as a lift amount of the valve. Is equivalent to the opening degree.

The vacuum pressure sensors 14 and 15 serving as detection units
Is a capacitance manometer for measuring the vacuum pressure in the reaction chamber 10 of FIG. Here, two capacitance manometers are selectively used according to the range of the vacuum pressure to be measured.

In the conventional vacuum pressure control system having such a configuration, when the controller 20 selects the forced close mode (CLOSE) as the operation mode, the sequence control circuit 23 causes the first solenoid valve 34 and the second The solenoid valve 35 is operated as shown in FIG. As a result, no compressed air is supplied into the pneumatic cylinder 41, and the inside of the pneumatic cylinder 41 communicates with the exhaust line, so that the air pressure in the pneumatic cylinder 41 becomes the atmospheric pressure and the vacuum proportional on-off valve 16 is shut off. .

When the controller 20 selects the vacuum pressure control mode (PRESS) as the operation mode, the sequence control circuit 23
Is operated, the time opening / closing operation valve 33 and the pneumatic cylinder 41 communicate with each other. As a result, the air pressure in the pneumatic cylinder 41 of the vacuum proportional on-off valve 16 is adjusted, and the valve lift can be operated by the pneumatic cylinder 41.

At this time, the vacuum pressure control circuit 22
Starts feedback control using a target vacuum pressure value specified by a local input or a remote input as a target value. That is, in FIG. 16, a vacuum pressure value in the reaction chamber 10 is measured by the vacuum pressure sensors 14 and 15, and a valve opening command value is output to the position control circuit 31 in accordance with a difference between the vacuum pressure value and the target vacuum pressure value. Thus, by operating the lift amount of the vacuum proportional on-off valve 16 to change the conductance of the exhaust system, the vacuum pressure in the reaction chamber 10 is kept constant at the target vacuum pressure value.

Therefore, in the prior art vacuum pressure system, the vacuum pressure control circuit 22 outputs the valve opening command value to the position control circuit 31 and operates the opening of the vacuum proportional on-off valve 16 to thereby control the exhaust system. Since the conductance can be varied widely and reliably, the reaction chamber 1 can be used over a wide range from atmospheric pressure or low vacuum close to atmospheric pressure to high vacuum.
The vacuum pressure within 0 can be accurately and constantly maintained at the target vacuum pressure value.

Further, in the controller 20, when the control deviation of the feedback control with respect to the vacuum pressure in the reaction chamber 10 is large, the operation amount of the feedback control is maximized, and the responsiveness of the feedback control is sufficiently ensured. ing. On the other hand, when the control deviation of the feedback control is small, the time constant is shifted stepwise to the preset time constant, and the vacuum pressure in the reaction chamber 10 can be maintained in a stable state.

More specifically, as shown in FIG. 17, the values obtained by adjusting the vacuum pressure values in the reaction chamber 10 measured by the vacuum pressure sensors 14 and 15 by the proportional differentiating circuits 105 and 106 are input on site or remote. After being compared with the target vacuum pressure value specified by the input, it is input to the proportional differential integration circuits 102 and 103. After that, the integrating circuit 104 connected in series becomes
To output to the position control circuit 31, a voltage in the range of 0 to 5V is output. The time constant of the integration circuit 104 is determined by the integration time adjustment circuit 101. Vacuum pressure sensor 1
When the measured values of 4 and 15 are far from the target vacuum pressure value, the internal operation circuit operates so that the integration time of the integration circuit is minimized. Thereby, the integration circuit 104
Functions as an amplifier circuit having an almost infinite gain. That is, the measurement values of the vacuum pressure sensors 14 and 15>
In the case of the target vacuum pressure value, 5 V which is the maximum value of the integration circuit 104 is output to the position control circuit 31. As a result, the vacuum proportional on-off valve 16 operates in a direction to open rapidly.

When the measured values of the vacuum pressure sensors 14 and 15 <the target vacuum pressure value, 0 V which is the minimum value of the integration circuit 104 is output to the position control circuit 31. As a result, the vacuum proportional on-off valve 16 operates in a direction to rapidly close. By these operations, the valve opening (valve lift amount) of the vacuum proportional on-off valve 16 can reach the position near the target vacuum pressure value in the shortest time. After that, the integration time adjusting circuit 101, which has determined that it has reached near the position for achieving the target vacuum pressure value, maintains the vacuum pressure at that position in a stable state.
An operation of shifting to the time constant of 04 stepwise is performed.

[0021]

However, in the prior art vacuum pressure control system, the CVD system shown in FIG.
Regarding the reaction chamber 10 of the apparatus, the vacuum proportional on-off valve 16
Since a material gas such as dichlorsilane which tends to precipitate on the gas contact surface of the reaction chamber is often supplied from the inlet 11, the vacuum proportional on-off valve 16 through which the material gas in the reaction chamber 10 passes is periodically decomposed, cleaned and cleaned. Had to be reassembled.

When the vacuum proportional on-off valve 16 is reassembled, the poppet valve body 45 is re-assembled due to a difference in the tightening force at the time of reassembly and a change with time of the O-ring 50 provided on the poppet valve body 45. Vacuum proportional on-off valve 16 immediately after starting to move
Of the valve (valve lift amount) changes.

Accordingly, for example, when changing the vacuum pressure in the reaction chamber 10 from a high vacuum pressure to a target vacuum pressure value near the atmospheric pressure, 0 V which is the minimum value of the integration circuit 104 is applied to the position control circuit 31. The O-ring 50 provided on the poppet valve body 45 is brought into close contact with the valve seat 47, the vacuum proportional on-off valve 16 is closed, and the vacuum pressure in the reaction chamber 10 is changed from a high vacuum pressure to a pressure near the atmospheric pressure. Once the target vacuum pressure value is rapidly approached, the vacuum pressure control circuit 2
2 outputs the valve opening command value to the position control circuit 31 and operates the opening of the vacuum proportional on-off valve 16, the opening of the vacuum proportional on-off valve 16 immediately after the poppet valve body 45 starts moving (the valve Of the vacuum proportional on-off valve 16 may be longer than before the re-assembly of the vacuum proportional on-off valve 16 due to the change of the lift amount of the vacuum chamber. As a result, the vacuum pressure in the reaction chamber 10 sometimes exceeded the target vacuum pressure value (overshoot). Similarly, the time until the discharge of the material gas in the reaction chamber 10 is started may be shorter than that before the vacuum proportional on-off valve 16 is reassembled. When the vacuum pressure in the reaction chamber 10 is slowly changed from the atmospheric pressure toward the absolute vacuum direction when the pressure is in the shut-off state, the vacuum pressure in the reaction chamber 10 goes too far with respect to the target vacuum pressure value ( Undershoot).

Also, when the vacuum proportional on-off valve 16 is reassembled, the difference in tightening force at the time of reassembly, the aging of the O-ring 50 provided on the poppet valve body 45, the electrical aging, etc. Since the positional relationship between the valve seat 47 and the potentiometer 18 changes up and down as compared to that before reassembly of the vacuum proportional on-off valve 16, even if the opening degree of the vacuum proportional on-off valve 16 is the same value, the vacuum proportional on-off Before and after reassembly of the valve 16,
The output value of the potentiometer 18 for measuring the opening degree of the vacuum proportional on-off valve 16 will be different.

On the other hand, when performing feedback control in which the vacuum pressure in the reaction chamber 10 is kept constant at the target vacuum pressure value, while measuring the opening degree of the vacuum proportional on-off valve 16 with the output value of the potentiometer 18, The opening of the vacuum proportional on-off valve 16 is being operated in accordance with the valve opening command value output from the pressure control circuit 22, and the opening of the vacuum proportional on-off valve 16 has reached the opening corresponding to the valve opening command value. Since the determination is made based on the output value of the potentiometer 18, there is a one-to-one electrical correspondence between the output value of the potentiometer 18 and the valve opening command value output from the vacuum pressure control circuit 22. That is, the valve opening command value has a one-to-one correspondence with the opening of the vacuum proportional on-off valve 16 via the output value of the potentiometer 18.

Therefore, when the output value of the potentiometer 18 shifts, after the reassembly of the vacuum proportional on-off valve 16, the correspondence between the valve opening command value and the opening degree of the vacuum proportional on-off valve 16 also changes. Will occur. If the deviation between the correspondence between the valve opening command value and the opening of the vacuum proportional on-off valve 16 is large, from the range of the electrical correspondence between the output value of the potentiometer 18 and the valve opening command value, A part of the control range of the opening degree of the vacuum proportional on-off valve 16 may be deviated,
After the reassembly of the vacuum proportional on-off valve 16, it may not be possible to correct the deviation of the correspondence between the opening degree of the vacuum proportional on-off valve 16 and the valve opening command value.

Accordingly, the present invention has been made to solve the above-described problem, and the valve opening command value immediately after the valve element of the vacuum proportional on-off valve has started to move is defined as the valve opening command value. To provide a vacuum pressure control system that controls the degree of opening of a vacuum proportional on-off valve as the lowest point, thereby preventing the vacuum pressure in a vacuum vessel from being excessively high with respect to a target vacuum pressure value. Aim. It is another object of the present invention to provide a vacuum pressure control system that corrects a shift in the correspondence between the opening degree of the vacuum proportional on-off valve and the valve opening command value after reassembly of the vacuum proportional on-off valve.

[0028]

In order to achieve the above object, the invention according to the first aspect of the present invention is directed to a method of manufacturing a vacuum pump by changing an opening degree on a pipe connecting a vacuum vessel and a vacuum pump. A vacuum proportional on-off valve for changing the vacuum pressure in the container, a vacuum pressure sensor for measuring the vacuum pressure in the vacuum container, and a valve opening command generated based on an output value of the vacuum pressure sensor and a target vacuum pressure value. A controller for controlling the degree of opening of the vacuum proportional on-off valve by a value, wherein the vacuum proportional on-off valve is provided with a valve seat, and an elastic seal member that abuts or separates from the valve seat. The valve opening command value corresponding to the output value of the valve opening sensor when the valve body is in close contact with the valve seat, the initial opening of the vacuum proportional on-off valve And treat it as a zero By treating it as the lowest point in controlling the opening degree of the vacuum proportional on-off valve, when changing the vacuum pressure in the vacuum vessel, it is possible to prevent the vacuum pressure from going too far with respect to the target vacuum pressure value. I do.

The invention according to claim 2 is the vacuum pressure control system according to claim 1, wherein the valve opening command value corresponding to the initial zero point of the opening of the vacuum proportional on-off valve is gradually increased. Controlling the opening degree of the vacuum proportional on-off valve while changing the valve body, and automatically treating the valve opening degree command value immediately after the valve element starts moving as a new zero point of the opening degree of the vacuum proportional on-off valve. It is characteristically performed. Claim 3
The invention according to the vacuum pressure control system according to claim 2, wherein when treating as a new zero point of the opening degree of the vacuum proportional on-off valve, the valve element immediately after the valve element starts to move Controlling the degree of opening of the vacuum proportional on-off valve until the valve is farthest away from the valve seat in a controlled manner, and correcting for a zero point deviation of the degree of opening of the vacuum proportional on-off valve due to reassembly or aging of the vacuum proportional on-off valve In the electrical relationship between the output value of the valve opening sensor and the valve opening command value. The invention according to claim 4 is the vacuum pressure control system according to claim 2 or 3, wherein the valve opening command value corresponding to the zero point of the opening of the vacuum proportional on-off valve is set to the controller. And is stored.

According to a fifth aspect of the present invention, there is provided the vacuum pressure control system according to any one of the second to fourth aspects, wherein the opening degree of the vacuum proportional on-off valve is measured. A sensor is provided, and the valve opening command value corresponding to a zero point of the opening of the vacuum proportional on-off valve is calculated based on an output of the valve opening sensor.

According to a sixth aspect of the present invention, there is provided the vacuum pressure control system according to any one of the second to fourth aspects, wherein a pneumatic cylinder serving as a drive source of the vacuum proportional on-off valve is provided. An air pressure sensor that measures the air pressure in the air pressure cylinder, and calculates the valve opening command value corresponding to the zero point of the opening of the vacuum proportional on-off valve based on the output of the air pressure cylinder. I do.

In the vacuum pressure control system of the present invention having such specific items, the vacuum pump sucks the gas in the vacuum vessel to make the inside of the vacuum vessel vacuum. Here, the vacuum pump is performing a constant suction, and by changing the opening of the vacuum proportional on-off valve, the amount of gas sucked by the vacuum pump from the vacuum container is adjusted, and the vacuum pressure in the vacuum container is changed. Let me. Further, the vacuum pressure sensor measures the vacuum pressure in the vacuum container. The controller controls the opening of the vacuum proportional on-off valve based on the valve opening command value so that the target vacuum pressure matches the output value of the vacuum pressure sensor. At this time, while measuring the opening of the vacuum proportional on-off valve with the output value of the valve opening degree sensor, the opening of the vacuum proportional on-off valve is controlled in accordance with the valve opening command value generated from the controller. Is determined by the output value of the valve opening sensor, the output value of the valve opening sensor and the valve opening command value are determined by the output value of the valve opening sensor. There is a one-to-one electrical correspondence.

When the vacuum pressure control system according to the present invention is started, the valve opening command value corresponding to the output value of the valve opening sensor when the valve body is in close contact with the valve seat is received by the valve body. The opening of the vacuum proportional on-off valve immediately after it starts moving is treated as the initial zero point of the vacuum proportional on-off valve. Furthermore, by treating the valve opening command value corresponding to the output value of the valve opening sensor when the valve body is in close contact with the valve seat as the lowest point in controlling the opening of the vacuum proportional on-off valve, The dead band characteristic of the vacuum proportional on-off valve is eliminated.

On the other hand, when the vacuum proportional on-off valve is reassembled, the valve body may be damaged due to a difference in tightening force at the time of reassembly, a change with time of the elastic member provided on the valve body, a change in electrical events, and the like. Immediately after the movement starts, the opening of the vacuum proportional on-off valve changes. Therefore, even if the valve opening command value is changed stepwise or rampwise from the lowest point to operate the opening of the vacuum proportional on-off valve from the shut-off state of the vacuum proportional on-off valve, immediately after the valve element starts to move. By changing the opening degree of the vacuum proportional on-off valve in the above, the time until the discharge of gas in the vacuum chamber is started (again) may be longer or shorter than that before reassembly of the vacuum proportional on-off valve. is there. At the same time, the output value of the valve opening sensor that measures the opening of the vacuum proportional on-off valve will be different. Therefore, after reassembly of the vacuum proportional on-off valve, the valve opening command value and the opening of the vacuum proportional on-off valve will be Will also be shifted.

Therefore, in the vacuum pressure control system of the present invention, after the reassembly of the vacuum proportional on-off valve, the valve opening command value corresponding to the opening degree of the vacuum proportional on-off valve immediately after the valve element starts moving is newly added. It automatically treats as the zero point of the opening of the vacuum proportional on-off valve, and automatically treats it as the lowest point in controlling the opening of the vacuum proportional on-off valve. Is stored and held in the controller. Thus, before and after reassembly of the vacuum proportional on-off valve, even if the opening degree of the vacuum proportional on-off valve immediately after the valve element starts to move, the vacuum proportional on-off valve is changed from the shut-off state to the vacuum proportional on-off valve. When operating the opening of the vacuum chamber, the time until the discharge of the gas in the vacuum chamber is started again can be the same, so when changing the vacuum pressure in the vacuum vessel to atmospheric pressure or near atmospheric pressure, In addition, overshoot (overshoot) with respect to the target vacuum pressure value can be prevented. Similarly, the time until gas discharge in the vacuum chamber is started can be made the same, so that when the vacuum proportional on-off valve is in the shut-off state, the vacuum pressure in the vacuum chamber is changed from the atmospheric pressure to the absolute pressure. Even when the pressure is slowly changed in the vacuum direction, it is possible to prevent the vacuum pressure in the vacuum chamber from exceeding the target vacuum pressure value (undershoot).

However, if the correspondence between the valve opening command value after reassembly of the vacuum proportional on-off valve and the opening of the vacuum proportional on-off valve is large, the vacuum proportional on-off valve immediately after the valve element starts to move. When the valve opening command value corresponding to the opening of the valve is treated as the zero point of the opening of the new vacuum proportional on-off valve, the valve is controlled to be most separated from the valve seat immediately after the valve starts to move. A part of the control range of the opening of the vacuum proportional on-off valve up to the above may not be within the electrical correspondence between the output value of the valve opening sensor and the valve opening command value. Therefore, when treating as a zero point of the opening degree of the new vacuum proportional on-off valve, the opening degree of the vacuum proportional on-off valve from immediately after the valve body starts to move until the valve body is most controllably separated from the valve seat. Control is ensured within the electrical correspondence between the output value of the valve opening sensor and the valve opening command value. This makes it possible to correct the deviation of the correspondence between the opening degree of the vacuum proportional on-off valve and the valve opening command value after the reassembly of the vacuum proportional on-off valve.

The automatic calculation of the zero point of the degree of opening of the new vacuum proportional on-off valve can be carried out, for example, by the following procedure. First, in the vacuum proportional on-off valve after the reassembly, the valve body is brought into close contact with the valve seat and is mechanically set at the lowest point.

Then, a valve opening command value corresponding to the output value of the valve opening sensor when the valve body is in close contact with the valve seat is determined as a provisional valve opening command value, and the provisional valve opening command value is gradually reduced. Operate the opening of the vacuum proportional on-off valve while changing to. afterwards,
The valve opening command value immediately after the valve element starts moving is set as the zero point of the opening of the new vacuum proportional on-off valve. Note that the time immediately after the valve element starts moving is determined by the fact that the output value of the valve opening degree sensor has started to fluctuate.

When a pneumatic cylinder serving as a drive source of the vacuum proportional on-off valve and a pneumatic sensor for measuring the air pressure of the pneumatic cylinder are provided, when the valve body is in close contact with the valve seat, the pneumatic cylinder Operate the opening of the vacuum proportional on-off valve while gradually changing the air pressure of After that, the air pressure in the pneumatic cylinder when the vacuum pressure in the vacuum vessel changes slightly is measured by an air pressure sensor, and a valve opening command value for realizing an air pressure that is appropriately lower than the measured air pressure is added to a new value. This is the zero point of the opening of the vacuum proportional on-off valve. still,
The point in time when the vacuum pressure in the vacuum vessel slightly changes is determined by the fact that the output value of the vacuum pressure sensor has started to fluctuate.

That is, in the vacuum pressure control system of the present invention, the valve opening command value corresponding to the opening of the vacuum proportional on-off valve immediately after the valve element starts moving is set to the new zero point of the opening of the vacuum proportional on-off valve. By treating it as the lowest point in the control of the opening of the vacuum proportional on-off valve, before and after reassembly of the vacuum proportional on-off valve, Even when the opening changes, when the vacuum proportional on-off valve is closed and the opening of the vacuum proportional on-off valve is operated, the time until gas discharge in the vacuum chamber starts (again) must be the same. Therefore, when changing the vacuum pressure in the vacuum vessel, it is possible to prevent the vacuum pressure from going too far with respect to the target vacuum pressure value.

Further, when the valve is treated as a zero point of the opening degree of the new vacuum proportional on-off valve, immediately after the valve element starts moving, the vacuum proportional on-off valve is controlled from the valve seat until it is most separated from the valve seat. Since the opening control is ensured within the electrical correspondence between the output value of the valve opening sensor and the valve opening command value, the vacuum proportional on-off valve is reassembled after the vacuum proportional on-off valve is reassembled. The deviation of the correspondence between the opening and the valve opening command value can be corrected.

[0042]

Embodiments of the present invention will be described below with reference to the drawings. The vacuum pressure control system according to the present embodiment has a configuration similar to that of the conventional vacuum pressure control system. Therefore, the vacuum pressure control system according to the present embodiment measures the vacuum pressure in the reaction chamber 10 of the CVD apparatus provided on the semiconductor manufacturing line with the vacuum pressure sensors 14 and 15 as described in the section of the related art. Then, a difference from an externally applied target vacuum pressure value is obtained, and the controller 20 generates a valve opening command value in accordance with the difference, and the air pressure control unit 30 controls the vacuum proportional opening / closing in accordance with the valve opening command value. By operating the opening of the valve 16, the vacuum pump 1
By changing the conductance of the exhaust system up to 3, the vacuum pressure in the reaction chamber 10 from which gas is discharged by the vacuum pump 13 is kept constant at a target vacuum pressure value in the range from atmospheric pressure to high vacuum pressure. This is to perform feedback control.

At this time, the air pressure control unit 30 measures the opening degree of the vacuum proportional on-off valve 16 based on the output value of the potentiometer 18 and, while measuring the opening degree of the vacuum proportional on-off valve 16 in accordance with the valve opening command value.
Since the opening of the vacuum proportional on-off valve 16 has been adjusted to the opening in accordance with the valve opening command value, the output value of the potentiometer 18 is used. And the valve opening command value generated by the controller 20 are in one-to-one electrical correspondence.

For example, when the valve opening command value generated by the controller 20 is in the range of 0 to 5 V, the potentiometer 1
In the case where the output value 8 is generated via the amplifier 19 in the range of 1 to 5 V, there is a one-to-one electrical correspondence as shown in FIG. The distance (opening degree of the valve) of the poppet valve element 45 from the valve seat 47 is also determined by the potentiometer 18.
Have a one-to-one correspondence with the output value generated via the amplifier 19. That is, the valve opening command value has a one-to-one correspondence with the opening of the vacuum proportional on-off valve 16 via the output value of the potentiometer 18.

When the vacuum pressure control system according to the present embodiment is started up, the valve corresponding to the output value (1.2 V) of the potentiometer 18 when the poppet valve element 45 is in close contact with the valve seat 47. Opening command value (0.25V)
Is set as the opening degree of the vacuum proportional on-off valve 16 immediately after the poppet valve element 45 starts to move.
Is treated as the zero point of the opening.

On the other hand, when the vacuum proportional on-off valve 16 is reassembled, the difference in the tightening force at the time of reassembly, the aging of the O-ring 50 provided on the poppet valve body 45, the aging of electrical characteristics, etc. The opening degree of the vacuum proportional on-off valve 16 immediately after the poppet valve element 45 starts to move changes.

Further, when the vacuum proportional on-off valve 16 is reassembled, the positional relationship between the valve seat 47 and the potentiometer 18 changes up and down as compared with that before the vacuum proportional on-off valve 16 is reassembled. Even if the opening of the on-off valve 16 has the same value, before and after reassembly of the vacuum proportional on-off valve 16, the potentiometer 1 measures the opening of the vacuum proportional on-off valve 16.
8 will be different. Therefore, since the output value of the potentiometer 18 shifts, after the reassembly of the vacuum proportional on-off valve 16, the correspondence between the valve opening command value and the opening degree of the vacuum proportional on-off valve 16 also shifts.

Therefore, in the vacuum pressure control system of the present embodiment, when the vacuum proportional on-off valve 16 is reassembled, it corresponds to the opening degree of the vacuum proportional on-off valve 16 immediately after the poppet valve body 45 starts moving. The valve opening command value is set as a new zero point of the opening of the vacuum proportional on-off valve 16 in place of the initial zero of the opening of the vacuum proportional on-off valve 16, and the controller 2 shown in FIG.
The ZERO point correction circuit 121 automatically calculates the zero point and stores the value in the controller 20. ZE in FIG.
An example of a procedure of calculation by the RO point correction circuit 121 will be described with reference to the flowchart of FIG. However, the ZER of FIG.
When the zero point of the opening of the new vacuum proportional on-off valve 16 is calculated by the O point correction circuit 121, the vacuum proportional on-off valve 16
, The poppet valve body 45 is brought into close contact with the valve seat 47,
Keep it at the lowest point mechanically.

At S1 in FIG. 1, it is determined whether or not the poppet valve body 45 is mechanically at the lowest point based on the output value of the potentiometer 18. If it is determined that the poppet valve 45 is not mechanically located at the lowest point (S1: No), the process proceeds to S12 and returns to the main program. When it is determined that the poppet valve 45 is at the position (S1: Yes), the process proceeds to S2, and the output value of the potentiometer 18 when the poppet valve body 45 is mechanically determined to be at the lowest point is acquired. Then, in S3, a valve opening command value corresponding to the output value of the potentiometer 18 obtained in S2 is obtained as a provisional valve opening command value. For example, as shown in FIG.
If the valve opening command value is in the range of 0 to 5 V and the output value of the potentiometer 18 is in the range of 1 to 5 V, S2
The output value of the potentiometer 18 obtained in the step is Y (V),
Assuming that the provisional valve opening command value is X (V), calculation is performed using a proportional expression of (Y-1) :( X-0) = (5-1) :( 5-0).

In step S4, a valve opening command value serving as a determination point is set based on the output value of the potentiometer 18 obtained in step S2. This determination point is determined in advance in consideration of the time required to fill the air pressure in the pneumatic cylinder 41 serving as the drive source of the vacuum proportional on-off valve 16 to a value required until the poppet valve body 45 starts moving. Then, in S5, the provisional valve opening command value calculated in S4 is output.

Thereafter, in S6, it is determined whether the provisional valve opening command value exceeds the valve opening command value serving as a determination point. If it is determined that the provisional valve opening command value exceeds the valve opening command value serving as a determination point (S6: Yes), the process proceeds to S7.
A flag indicating that the value has been exceeded is stored inside the controller 20. Then, the process proceeds to S8, a value obtained by subtracting 15 mV from the provisional valve opening command value is set as a new provisional valve opening command value, and the process returns to S6.

On the other hand, when it is determined that the provisional valve opening command value does not exceed the valve opening command value serving as the determination point (S6:
No), the process proceeds to S9, and it is determined whether or not a flag indicating that the value has been exceeded is set. If it is determined that the flag indicating that it has exceeded is set (S9: Yes), the process proceeds to S11, and the provisional valve opening command value is determined as a new zero point of the opening of the vacuum proportional on-off valve 16. On the other hand, when it is determined that the flag indicating the overrun is not set (S9: No),
Proceeding to S10, a value obtained by adding 15 mV to the provisional valve opening command value is set as a new provisional valve opening command value, the process returns to S6, and the above processing is repeated until the process proceeds to S11.

FIG. 5 shows a case where the provisional valve opening command value acquired in S3 already exceeds the valve opening command value serving as a determination point, and a new zero point of the opening of the vacuum proportional on-off valve 16 is determined. FIG. In this case, S6
After repeating the loop process of → S7 → S8 → S6 twice, the process proceeds to S11, where a new zero point of the opening degree of the vacuum proportional on-off valve 16 is determined. FIG. 6 shows a case where the provisional valve opening command value acquired in S3 has not yet exceeded the valve opening command value serving as a determination point, and the new vacuum proportional on-off valve 16
FIG. 7 is a diagram for explaining the progress until the zero point of the opening degree is determined. In this case, after the loop processing of S6 → S9 → S10 → S6 is repeated twice, the loop processing of S6 → S7 → S8 → S6 is performed once, and then the process proceeds to S11, where a new vacuum proportional on-off valve 16 is set. Is determined.

The mechanical reference point shown in FIGS. 5 and 6 corresponds to the position where the poppet valve element 45 is mechanically located at the lowest point and the inside of the pneumatic cylinder 41 serving as a drive source of the vacuum proportional on-off valve 16. Means that the air pressure is at atmospheric pressure. Therefore, the zero point of the opening degree of the new vacuum proportional on-off valve 16 determined by the flowchart of FIG. 1 is slightly lower than the determination value, so that the filling of the air pressure in the pneumatic cylinder 41 is considered. , The valve opening command value immediately after the poppet valve element 45 starts moving.

That is, the ZERO point correction circuit 1 shown in FIG.
In the flowchart of FIG. 1, which is an example of the procedure for calculating the zero point of the opening degree of the new vacuum proportional on-off valve 16 at 21, the output of the potentiometer 18 when the poppet valve body 45 is in close contact with the valve seat 47 in S 3. The valve opening command value corresponding to the value is obtained as a provisional valve opening command value, and the zero point of the opening degree of the new vacuum proportional on-off valve 16 determined in S11 is calculated from the provisional valve opening command value acquired in S3. The valve opening command value slightly changed (see FIGS. 5 and 6). Then, the zero point of the opening of the new vacuum proportional on-off valve 16 determined in S11 is slightly lower than the determination value, and thus becomes the valve opening command value immediately after the poppet valve body 45 starts moving. .

The ZERO point correction circuit 121 shown in FIG.
The following is an example of a procedure for calculating a new zero point of the opening degree of the vacuum proportional on-off valve 16 in the following. For example, a valve opening command value corresponding to the output value of the potentiometer 18 when the poppet valve element 45 is in close contact with the valve seat 47 is obtained as a provisional valve opening command value. This calculation method is the same as the calculation method of S3 in FIG. Then, the air pressure control unit 30 operates the opening of the vacuum proportional on-off valve 16 while gradually changing the provisional valve opening command value. Thereafter, when the output value of the potentiometer 18 starts to change, the time point immediately after the poppet valve element 45 starts moving is specified, and the valve opening command value immediately after the poppet valve element 45 starts moving is used as a new vacuum proportional on-off valve. It is assumed that the opening degree is 16 zero. As described above, the zero point of the opening degree of the new vacuum proportional on-off valve 16 calculated by the automatic teaching is:
As shown in FIG. 3, this is taken into consideration when the controller 20 generates a valve opening command value via the zero point correction program.

If the zero point of the opening degree of the new vacuum proportional on-off valve 16 is to be used as the valve opening command value immediately before the poppet valve body 45 starts moving, the valve immediately after the poppet valve body 45 starts moving will be described. With respect to the opening command value, a value obtained by slightly changing the opening of the vacuum proportional on-off valve 16 in the closing direction is set as a new zero point of the opening of the vacuum proportional on-off valve 16.

The ZERO point correction circuit 121 shown in FIG.
The following is an example of a procedure for calculating a new zero point of the opening degree of the vacuum proportional on-off valve 16 in the following. For example, when the poppet valve body 45 is in close contact with the valve seat 47, the opening of the vacuum proportional on-off valve 17 is operated by the air pressure control unit 30 while gradually changing the air pressure of the air pressure cylinder 41. Here, gradually changing the air pressure of the air pressure cylinder 41 is as follows.
Using the air pressure sensor 70 that measures the air pressure of the pneumatic cylinder 41, the bias control circuit 110 shown in FIG. For example, the air pressure of the air pressure cylinder 41 is gradually changed stepwise or ramp-wise.

Thereafter, the air pressure in the pneumatic cylinder 41 when the vacuum pressure in the reaction chamber 10 slightly changes is measured by the air pressure sensor 70, and a valve opening command for realizing an air pressure appropriately lower than the measured air pressure. The value is set as the zero point of the opening degree of the new vacuum proportional on-off valve 16. Here, the valve opening command value for realizing an air pressure that is appropriately lower than the air pressure measured by the air pressure sensor 70 is changed to a new vacuum proportional on-off valve 16.
The zero point of the opening degree is determined by the O-ring 50 provided on the poppet valve body 45 immediately after the poppet valve body 45 starts moving.
This is because the discharge of the material gas in the reaction chamber 10 has not yet started due to the elastic deformation of the gas. The reaction chamber 1
The time point immediately after the vacuum pressure of 0 slightly changes is specified by the start of the fluctuation of the measurement values of the vacuum pressure sensors 14 and 15. Thereby, the zero point of the opening degree of the new vacuum proportional on-off valve 16 becomes the valve opening degree command value immediately after the poppet valve body 45 starts moving.

Using the lower limit value limiting circuit 120 shown in FIG. 10, the output range of the valve opening command value shown in FIG.
As shown in the output range of the valve opening command value in FIG.
The zero point of the opening degree of the new vacuum proportional on-off valve 16 determined by the RO point correction circuit 121 is set as the lowest point in control of the vacuum proportional on-off valve 16.

Thus, in the vacuum pressure control system according to the present embodiment, the valve opening command value corresponding to the opening of the vacuum proportional opening / closing valve 16 immediately after the poppet valve body 45 starts moving is changed to a new vacuum proportional opening / closing valve. By treating it as the zero point of the valve opening degree and treating it as the lowest point in controlling the opening degree of the vacuum proportional on-off valve 16, the poppet valve body 45 before and after reassembly of the vacuum proportional on-off valve 16 is Even if the opening of the vacuum proportional on-off valve 16 changes immediately after it starts moving, when the opening of the vacuum proportional on-off valve 16 is operated from the shut-off state of the vacuum proportional on-off valve 16, the material gas in the reaction chamber 10 is Since the time until the discharge is started again can be made the same, when the vacuum pressure in the reaction chamber 10 is changed to the atmospheric pressure or near the atmospheric pressure, the pressure may be too large for the target vacuum pressure value (overshoot). It is possible to prevent the door).

For example, FIG. 8 shows that the vacuum pressure in the reaction chamber 10 is fed back at or near atmospheric pressure without setting the zero point of the opening of the new vacuum proportional on-off valve as the lower limit of the valve opening command value. This is an example showing the progress of control, but the poppet valve body 45 starts to separate from the valve seat 47 due to a change in the opening degree of the vacuum proportional on-off valve 16 immediately after the poppet valve body 45 starts to move. However, a response delay of time t3 occurs. As a result, when performing feedback control of the vacuum pressure in the reaction chamber 10 at or near the atmospheric pressure, the vacuum pressure in the reaction chamber 10 will overshoot the target vacuum pressure value (overshoot).

FIG. 7 shows a new vacuum proportional on-off valve 16.
Is set to the lower limit of the valve opening command value, and the reaction chamber 10
This is an example showing the progress of the feedback control of the vacuum pressure in the inside at or near atmospheric pressure, but the lower limit of the valve opening command value is set to the value of the vacuum proportional on-off valve 16 immediately after the poppet valve body 45 starts moving. Because it corresponds to the opening,
There is no response delay when the poppet valve element 45 starts to separate from the valve seat 47. As a result, when performing feedback control of the vacuum pressure in the reaction chamber 10 at or near atmospheric pressure, the vacuum pressure in the reaction chamber 10 does not overshoot (overshoot) the target vacuum pressure value.

The fact that no response delay occurs when the poppet valve element 45 begins to separate from the valve seat 47 is caused by the fact that the vacuum proportional on-off valve 16 is in the shut-off state as shown in FIG.
This is effective when the vacuum pressure in the reaction chamber 10 is slowly changed from the atmospheric pressure toward the absolute vacuum. This is because if a response delay occurs and the progress of the vacuum pressure in the reaction chamber 10 toward the absolute vacuum direction is slightly excessive (undershoot), the gas flow in the reaction chamber 10 becomes faster and particles are generated, This is because the quality of the wafer in the reaction chamber 10 deteriorates.

FIG. 2 shows an example of the relationship between the output value of the potentiometer 18, the valve opening command value, and the opening of the vacuum proportional on-off valve 16 before and after reassembly of the vacuum proportional on-off valve 16. Here, as in FIG. 4, the valve opening command value is in the range of 0 to 5 V and the output value of the potentiometer 18 is in the range of 1 to 5 V. The output values are in one-to-one electrical correspondence. The range of the output value of the potentiometer 18 from 1 to 5 V corresponds to the range of the opening degree (valve lift amount) of the vacuum proportional on-off valve 16 from 0 to 31.112 mm.

Before reassembly of the vacuum proportional on-off valve 16, for example, at the time of setting (B) when the vacuum proportional on-off valve 16 is shipped, the valve opening command value of 0.25 V (at this time, the potentiometer 18 The output value is 1.2 V) is treated as the initial zero point of the opening of the vacuum proportional on-off valve 17.

After the reassembly of the vacuum proportional on-off valve 16, for example, when the zero point of the opening of the vacuum proportional on-off valve 16 is shifted upward (A), the valve opening command value of 0 V (at this time) (The output value of the potentiometer 18 is 1.0 V) is treated as the zero point of the degree of opening of the new vacuum proportional on-off valve 17. When the zero point of the opening of the vacuum proportional on-off valve 16 shifts downward (C), the valve opening command value of 0.5 V (the output value of the potentiometer 18 at this time is 1.4 V) is newly added. The opening degree of the vacuum proportional on-off valve 17 is treated as a zero point.

The control range of the opening of the vacuum proportional on-off valve 16 is set at 28 m from immediately after the poppet valve body 45 starts moving.
m (in the range of 0 to 28 mm as the valve lift amount), the range of the valve opening command value is 0.25 to 4.25 when the vacuum proportional on-off valve 16 is set at the time of shipment (B). 75V,
When the zero point of the opening degree of the vacuum proportional on-off valve 16 shifts upward (A), 0 to 4.5 V, and when the zero point of the opening degree of the vacuum proportional on-off valve 16 shifts downward (C), the voltage drops to 0. It becomes 5-5V. In this manner, the opening degree of the vacuum proportional on-off valve 17 is controlled from immediately after the poppet valve element 45 starts to move until the poppet valve element 45 is farthest away from the valve seat 47 in a controlled manner (as the valve lift amount). (Range of 0 to 28 mm) is ensured within the electrical correspondence between the output value of the potentiometer 18 and the valve opening command value. Thereby, the vacuum proportional on-off valve 1
The deviation of the correspondence between the opening degree of the vacuum proportional on-off valve 16 and the valve opening command value after the reassembly of Step 6 can be corrected.

In the case of FIG. 2, when the output value of the potentiometer 18 and the opening degree of the vacuum proportional on-off valve 16 correspond to each other, the zero point of the opening degree of the vacuum proportional on-off valve 16 shifts upward (A). When it is greatly shifted with respect to (C) when it is shifted downward or downward, 28 mm from immediately after the poppet valve body 45 starts to move.
(In order to control the opening of the vacuum proportional on-off valve 16 in a range up to (valve lift amount of 0 to 28 mm), a valve opening command value range of 0 to 5 V is insufficient. Operation of the opening of the vacuum proportional on-off valve 16 will be hindered. Therefore, if the deviation is larger than this range, it is determined that there is an abnormality, the zero point correction is impossible, and an alarm is issued to perform error processing. The lower limit (C) of the correction and the upper limit (A) of the correction are
The setting is made in consideration of design tolerance, electrical error, aging of the O-ring 50, and the like.

Thus, in the vacuum pressure control system of the present embodiment, even after the vacuum proportional on-off valve 16 is reassembled, the deviation of the correspondence between the opening degree of the vacuum proportional on-off valve 16 and the valve opening command value is also corrected. can do.

The present invention is not limited to the above embodiment, and various changes can be made without departing from the gist of the present invention. For example, the vacuum pressure control system according to the present embodiment can be applied to a vacuum vessel of a semiconductor manufacturing line other than the reaction chamber 10 of the CVD apparatus.
For example, when used for a diffusion device in a semiconductor manufacturing line, when the vacuum pressure of the vacuum container is feedback-controlled at or near atmospheric pressure, the vacuum pressure in the vacuum container may exceed the target vacuum pressure value. , The operation of the relief valve provided in the vacuum vessel can be prevented, and the inside of the vacuum vessel can be prevented from communicating with the atmosphere.

[0072]

According to the vacuum pressure control system of the present invention, the valve opening command value corresponding to the opening of the vacuum proportional on-off valve immediately after the valve element starts moving is set to the new zero point of the opening of the vacuum proportional on-off valve. By treating it as the lowest point in the control of the opening of the vacuum proportional on-off valve, before and after reassembly of the vacuum proportional on-off valve, Even when the opening changes, when the vacuum proportional on-off valve is closed and the opening of the vacuum proportional on-off valve is operated, the time until gas discharge in the vacuum chamber starts (again) must be the same. Therefore, when changing the vacuum pressure in the vacuum vessel, it is possible to prevent the vacuum pressure from going too far with respect to the target vacuum pressure value.

Further, when handling the zero point of the opening degree of the new vacuum proportional on-off valve, the vacuum proportional on-off valve is controlled from immediately after the valve element starts moving until the valve element is farthest away from the valve seat in a controlled manner. Since the opening control is ensured within the electrical correspondence between the output value of the valve opening sensor and the valve opening command value, the vacuum proportional on-off valve is reassembled after the vacuum proportional on-off valve is reassembled. The deviation of the correspondence between the opening and the valve opening command value can be corrected.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an example of a procedure for calculating a zero point of an opening degree of a vacuum proportional on-off valve by a ZERO point correction circuit.

FIG. 2 is a diagram illustrating a deviation of a correspondence relationship between the opening degree of the vacuum proportional on-off valve and a valve opening command value after reassembly of the vacuum proportional on-off valve and a correction thereof.

FIG. 3 is a block diagram of a vacuum pressure control system according to the present embodiment.

FIG. 4 is a diagram illustrating an example of a correspondence relationship between an output value of a potentiometer and a valve opening command value;

FIG. 5 is a diagram illustrating an example calculated by the flowchart of FIG. 1;

FIG. 6 is a diagram illustrating an example calculated by the flowchart of FIG. 1;

FIG. 7 is a diagram showing the effect when the zero point of the opening of the vacuum proportional on-off valve is set to the lowest point of the valve opening command value after the reassembly of the vacuum proportional on-off valve.

FIG. 8 is a diagram illustrating a problem in a case where the zero point of the opening of the vacuum proportional on-off valve is not set to the lowest point of the valve opening command value after the reassembly of the vacuum proportional on-off valve.

FIG. 9 is a diagram showing an effect when the zero point of the opening of the vacuum proportional on-off valve is set to the lowest point of the valve opening command value after the reassembly of the vacuum proportional on-off valve.

FIG. 10 is a block diagram of a vacuum pressure control system according to the present embodiment.

FIG. 11 is a diagram illustrating an output range of the valve opening command value before the lower limit value limiting circuit limits the lower limit of the valve opening command value.

FIG. 12 is a diagram showing an output range of the valve opening command value after the lower limit of the valve opening command value is limited by the lower limit value limiting circuit.

FIG. 13 is a cross-sectional view of a state in which a vacuum proportional on-off valve is shut off.

FIG. 14 is a cross-sectional view of the open state of the vacuum proportional on-off valve.

FIG. 15 is a block diagram of a vacuum pressure control system according to the present embodiment.

FIG. 16 is a schematic view of an exhaust system of a reaction chamber of a CVD apparatus.

FIG. 17 is a block diagram of a vacuum pressure control system according to the present embodiment.

[Explanation of symbols]

 Reference Signs List 10 Reaction chamber of CVD apparatus 14, 15 Vacuum pressure sensor 16 Vacuum proportional on-off valve 18 Potentiometer 22 Vacuum pressure control circuit 41 Pneumatic cylinder 45 Poppet valve body 70 Air pressure sensor 110 Bias circuit 120 Lower limit value limiting circuit 121 Zero point correction circuit

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Hiroshi Kagohashi 850, Horinouchi-cho, Kasugai-shi, Aichi Prefecture F-term (reference) 3K045 AA02 AA12 AA38 BA22 BA36 CA04 CA12 DA12 DA50 3H052 AA01 BA35 CD09 DA04 EA01 EA09

Claims (6)

[Claims] A vacuum proportional on-off valve which is on a pipe connecting a vacuum container and a vacuum pump and changes an opening degree to change a vacuum pressure in the vacuum container; A vacuum pressure sensor for measuring, and a controller for controlling the opening of the vacuum proportional on-off valve with a valve opening command value generated based on an output value of the vacuum pressure sensor and a target vacuum pressure value. The vacuum proportional on-off valve, a valve seat, a valve body provided with an elastic seal member that abuts or separates from the valve seat, a valve opening degree sensor that measures the opening degree of the vacuum proportional on-off valve, The valve opening command value corresponding to the output value of the valve opening sensor when the valve body is in close contact with the valve seat is treated as an initial zero point of the opening of the vacuum proportional on-off valve, Vacuum proportional open By treating as the lowest point in the control of the opening degree of the valve closing, when changing the vacuum pressure in the vacuum vessel, it is possible to prevent the vacuum pressure from going too far with respect to the target vacuum pressure value. Control system. 2. The vacuum pressure control system according to claim 1, wherein the valve opening command value corresponding to the initial zero point of the opening of the vacuum proportional switching valve is gradually changed while gradually changing the valve opening command value. Controlling the opening degree, automatically treating the valve opening command value immediately after the valve element starts moving as the zero point of the opening degree of the new vacuum proportional on-off valve, Control system. 3. The vacuum pressure control system according to claim 2, wherein, when treating as a new zero point of the degree of opening of the vacuum proportional on-off valve, the valve element is moved to the valve seat immediately after the valve element starts moving. Controlling the degree of opening of the vacuum proportional on-off valve until the control is most distant from, and correcting for the deviation of the zero point of the degree of opening of the vacuum proportional on-off valve due to reassembly or aging of the vacuum proportional on-off valve, A vacuum pressure control system, wherein the value is secured within an electrical correspondence between an output value of the valve opening sensor and the valve opening command value. 4. The vacuum pressure control system according to claim 2, wherein the valve opening command value corresponding to the zero point of the opening of the vacuum proportional on-off valve is stored and held in the controller. A vacuum pressure control system. 5. The vacuum pressure control system according to claim 2, further comprising: a valve opening sensor that measures an opening of the vacuum proportional on-off valve; A vacuum pressure control system, wherein the valve opening command value corresponding to a zero point of the opening of the vacuum proportional on-off valve is calculated based on the output. 6. The vacuum pressure control system according to claim 2, wherein: a pneumatic cylinder serving as a drive source of the vacuum proportional on-off valve; and a pneumatic pressure measuring an air pressure in the pneumatic cylinder. A vacuum pressure control system comprising: a sensor; and calculating the valve opening command value corresponding to an initial zero point of the opening of the vacuum proportional on-off valve based on an output of the pneumatic cylinder.