JP5237220B2 - Vacuum pressure control system - Google Patents

Description

  The present invention relates to a vacuum pressure control system that performs slow pressure control of a semiconductor manufacturing apparatus to a predetermined pressure.

  For example, in a CVD apparatus of a semiconductor manufacturing apparatus, when a wafer and a material gas are reacted, it is necessary to control the pressure in a reaction furnace (vacuum vessel) from an atmospheric pressure to a high vacuum state. In this case, in particular, it is possible to suppress the scattering of particles by so-called slow exhaust, in which exhaust is gradually performed during the evacuation process when reaching a target vacuum pressure value from a low vacuum close to atmospheric pressure or the atmospheric pressure. Has become extremely important. For this reason, the CVD apparatus is provided with a vacuum pump for exhausting the air in the reaction furnace and an on-off valve for adjusting the evacuation by the vacuum pump, and when opening the vacuum by the vacuum pump, the opening degree of the on-off valve is adjusted. The particle is prevented from scattering by adjusting the pressure with high precision by slow exhaust from the reactor.

As a technique for adjusting the pressure of this type, for example, there is a vacuum pressure control system of Patent Document 1. In this vacuum pressure control system, the target vacuum pressure change point and the target vacuum pressure change speed are set in advance in the controller, and the opening of the vacuum proportional on-off valve is determined from the pressure value measured by the pressure sensor based on these settings. To control the process of pressure drop.
On the other hand, Patent Document 2 discloses a vacuum pressure control device having a vacuum proportional on-off valve provided with an elastic seal member. This vacuum pressure control device controls the vacuum pressure in the vacuum vessel by changing the amount of elastic deformation of the elastic seal member of the vacuum proportional on-off valve, and changing the amount of leakage from the elastic seal member, thereby reducing the pressure to atmospheric pressure. It is controlled in a low vacuum pressure region close to.

JP 2001-146975 A JP 2002-132354 A

However, in the vacuum pressure control system of Patent Document 1, when pressure control is performed from atmospheric pressure to a predetermined vacuum pressure for a predetermined time, a vacuum pressure amount change point and a target vacuum pressure change speed with respect to a required time until the vacuum pressure value are obtained. It is necessary to set the preset values in advance, and extra effort is required to obtain these preset values. For this reason, the operability has deteriorated.
On the other hand, since the vacuum pressure control device of Patent Document 2 is limited to the low vacuum region where the vacuum pressure is close to atmospheric pressure, it cannot control from low pressure close to atmospheric pressure or atmospheric pressure to high vacuum. The controllability was getting worse.

  The present invention was developed in order to solve the above-mentioned problems, and the object of the present invention is to easily control the pressure over a wide pressure range from low pressure to high pressure close to atmospheric pressure or atmospheric pressure, An object of the present invention is to provide a vacuum pressure control system that reliably prevents particle scattering by slow exhaust while controlling pressure with high accuracy.

In order to achieve the above object, an invention according to claim 1 includes an on-off valve provided in the middle of connecting a vacuum pump to a vacuum vessel and changing a vacuum pressure in the vacuum vessel, and a vacuum pressure in the vacuum vessel. A vacuum pressure control system that controls an opening degree of the on-off valve via a vacuum pressure sensor that measures a calculation function for calculating a reaching function that induces a pressure drop in the vacuum vessel; A timer for controlling opening and closing of the opening of the valve with an arbitrary time width, an open opening value that is an opening when the opening and closing valve is opened, and a closing opening value that is an opening when the opening and closing valve is closed Control unit means having a function of calculating from the output of the vacuum pressure sensor and the reaching function, a valve seat control mechanism for operating a valve seat which is a seat ring of the on-off valve, and operating a valve body of the on-off valve With the valve body control mechanism Driving means Ete driving the closing opening value and said open opening value, provided input means for command input the required time and the arrival pressure of the pressure drop from the outside, the target atmospheric pressure or any pressure A vacuum pressure control system characterized in that the pressure is reduced to an arbitrary pressure.

  According to the first aspect of the present invention, the control unit means, the drive means, and the input means are configured to reduce the atmospheric pressure or the arbitrary pressure to the target arbitrary pressure. By simply inputting, automatic pressure control can be easily performed up to the ultimate pressure in a wide pressure range, and it is possible to reliably prevent scattering of particles by performing slow exhaust while controlling pressure with high accuracy.

Further , if the calculation is performed by changing the optimum reaching function of the first, second or third order function according to the time from the pressure at the start of the pressure control to the arrival at the predetermined high vacuum pressure, an arbitrary reaching function is obtained. Even when the time required for the pressure drop is set, it is possible to perform slow exhaust while preventing the generation of particles by performing pressure control while changing the pressure drop process. For this reason, it is possible to reduce the time required for the slow exhaust while suppressing the scattering of particles.

In addition , the contact frequency of the seal part of the on-off valve can be suppressed during pressure control to prevent wear and wear of this seal part. Pressure control can be maintained.

It is the schematic diagram which showed one Embodiment of the vacuum pressure control system of this invention. It is sectional drawing which showed an example of the on-off valve. It is sectional drawing which shows the state which the seat ring of the on-off valve of FIG. 2 act | operated. It is explanatory drawing which showed control by the vacuum pressure control system of this invention. It is the graph which showed the example of the control waveform by an arrival function. (A) is the graph which showed the example of the control waveform by a linear function. (B) is the graph which showed the example of the control waveform by a quadratic function. It is the graph which showed the relationship between the time required for pressure drop, and pressure. It is sectional drawing which shows the state which the valve body of the on-off valve operated. It is the schematic diagram which showed the high-speed air control circuit.

  Hereinafter, an embodiment of a vacuum pressure control system according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a vacuum pressure control system of the present invention. A vacuum pressure control system main body (hereinafter referred to as system main body) 1 includes an on-off valve 2 and a vacuum pressure sensor 3, and a vacuum vessel 4 and a vacuum pump 5 are connected to the on-off valve 2. The vacuum vessel 4 forms a part of a CVD apparatus of a semiconductor manufacturing apparatus, for example, and is evacuated from the vacuum vessel 4 by a vacuum pump 5 connected to the vacuum vessel 4.

  The on-off valve 2 is connected to the vacuum vessel 4 via a vacuum pump 5 so that the vacuum pressure in the vacuum vessel 4 can be changed. The vacuum pressure sensor 3 is connected to the vacuum container 4 and measures the vacuum pressure in the vacuum container 4. The system main body 1 controls the opening degree of the on-off valve 2 via the on-off valve 2 and the vacuum pressure sensor 3. The system main body 1 further includes a control unit means 10 and a driving means (actuator) 12. And the input means 13, and the pressure inside the vacuum vessel 4 is reduced through these means while finely controlling the pressure from atmospheric pressure or an arbitrary pressure to an arbitrary target pressure. As a result, the system main body 1 supplies a material gas to a wafer (not shown) housed in the vacuum vessel 4 and performs a corresponding process on the wafer as the object to be processed.

  In the system main body 1, the on-off valve 2 is connected to the flow path portion 15 together with the vacuum container 4 and the vacuum pump 5, and controls the pressure in the vacuum container 4 by controlling the opening / closing of the on-off valve 2. The on-off valve 2 is composed of, for example, a butterfly valve, and a driving means 12 is connected to the valve body 16 of the on-off valve 2 as shown in FIG. The driving means 12 includes a valve seat control mechanism 20 that operates a valve seat 17 that is a seat ring of the on-off valve 2, and a valve body control mechanism 21 that operates a valve body 22 of the on-off valve 2. The opening degree value and the closing degree value are driven. The on-off valve is not limited to the butterfly valve, and may be an on-off valve having another structure.

  The valve body 16 has a body 23, and a flow path 24 is formed in the body 23. A valve body 22, a seat ring 17, a piston 26 and a spring 27 are built in the valve body 16. The valve body 22 is formed in a substantially disk shape, and is attached to a valve shaft 29 that is a rotating shaft by a fixing bolt 28, and can be rotated in a direction perpendicular to the flow path 24 by the valve shaft 29. Further, a mounting groove 30 is formed on the outer peripheral side of the valve body 22, and an O-ring 31 that is a seal ring is mounted in the mounting groove 30. The O-ring 31 is disposed on a side of the seat ring 17 that will be described later in contact with a valve seat seal portion 32, and the O-ring 31 can seal between the valve seat seal portion 32 and the valve body 22. . The valve shaft 29 is provided so as to be eccentric from the center of the valve body 22. Although not shown, the valve shaft 29 may be eccentric from the center of the flow path 24. A valve body control mechanism 21 is connected to the valve shaft 29, and the valve body control mechanism 21 enables the valve shaft 29 to be rotated with high accuracy at a desired rotation angle while suppressing a rotation error.

  As shown in the figure, the seat ring 17 is formed in a substantially annular shape, and is provided with a valve seat seal portion 32 and a sliding portion 33. Among these, the valve seat seal portion 32 is a portion that the O-ring 31 contacts and seals, and is formed on the inner peripheral surface side of the seat ring 17 in a tapered shape that gradually increases in diameter from the inner diameter side to the outer diameter side. Yes. The valve seat seal portion 32 may have a shape other than a tapered shape, for example, an arc shape. The sliding portion 33 is formed so that the entire seat ring 17 can slide in the body 23, and the sliding portion 33 is formed to protrude to the outer diameter side. A valve closing side regulating surface 34 and a valve opening side regulating surface 35 are formed on the side on which the sliding portion 33 moves.

  The seat ring 17 is attached to a mounting recess 36 formed inside the body 23 by mounting a sliding portion 33, and a flow path 24 is formed by a gap G provided between the sliding portion 33 and the mounting recess 36. The valve seat seal portion 32 can be brought into contact with and separated from the O-ring 31. At this time, the valve closing side regulating surface 34 comes into contact with the annular protrusion 37 formed in the mounting recess 36, and the valve opening side regulating surface 35 comes into contact with the contact surface 38 formed on the secondary side, respectively. The amount of movement of the ring 17 during reciprocation is regulated.

  As shown in FIG. 7, the piston 26 is formed in a substantially annular shape and is provided on the secondary side of the mounting recess 36, and in this embodiment is connected to the seat ring 17 by a plurality of shafts 39, 39 having two. ing. For this reason, the piston 26 can move in the mounting recess 36 integrally with the seat ring 17 via the shaft 39. An air flow path 40 is formed in the body 23 on the secondary side of the piston 26, and air can be supplied from the outside to the secondary side of the mounting recess 36 via the air flow path 40. A plurality of concave grooves 41 are formed on the primary side of the piston 26 in the body 23, and a spring 42 is mounted between the concave groove 41 and the piston 26 in a resilient state.

  The air flow path 40 provided on the piston 26 side is formed at a position where the piston 26 moves leftward in the drawing when air is supplied, and is further provided inside the actuator 12 mounted on the valve body 16. Connected to the air flow path portion 45. The air flow path portion 45 is branched from the middle into a first branch flow path 46 and a second branch flow path 47.

  With such a structure, the valve body 16 is normally urged to the right in the drawing by the elastic force of the spring 42 in the valve body 16, and the seat ring 17 connected to the piston 26 by the shaft 39 is also on the right side. It moves in the direction, that is, in the direction of the valve body 22, abuts and seals on the valve body 22 rotated in the valve closed state, and closes the flow path 24. On the other hand, when air is supplied through the air flow path 45, the piston 26 moves to the left in the figure against the urging force of the spring 27, and the seat ring 17 also moves to the left to close the valve. The flow path 24 is opened away from a certain valve body 22. Thus, the valve body 16 is of a so-called NC (normally closed) type that is normally closed. In the present embodiment, eight springs 27 are mounted at an equal angle in the circumferential direction of the piston 26. However, the springs 27 may be mounted by increasing or decreasing as necessary. Further, the number of shafts 39 may be increased or decreased as necessary.

  On the other hand, of the drive means connected to the valve body 16, the valve seat control mechanism 20 includes an electromagnetic valve 50, an electropneumatic regulator 51, and a pump 52. As shown in FIGS. 2 and 3, the electromagnetic valve 50 and the electropneumatic regulator 51 are connected in parallel to the first branch flow path 46 and the second branch flow path 47 of the drive means 12. Connected to the outside (or inside). A pump 52 is connected to the electromagnetic valve 50 and the electropneumatic regulator 51, and when air for operation is supplied through the pump 52, the air is controlled by an air control unit 55 described later, whereby the electromagnetic valve 50 is controlled. And the electropneumatic regulator 51 are respectively operated to control the opening / closing of the flow path 24 by the seat ring 17.

  The electromagnetic valve 50 can be operated in a valve open state or a valve closed state, and air from the pump 52 can be supplied to the air flow path 40 or stopped in each state. On the other hand, the electropneumatic regulator 51 can adjust the supply pressure of air from the pump 52 by adjusting the valve opening. The electropneumatic regulator 51 may be any device that controls the amount of air supplied to the valve body 16 so that the pressure is controlled within a range of 0 to 0.5 MPa by an internal piston (not shown), or As long as the position of the seat ring 17 can be controlled by the ON / OFF control of the supply pressure, any method may be used.

  The internal structure of the solenoid valve 50 and the electropneumatic regulator 51 is omitted. However, if the solenoid valve 50 is an on / off on-off valve and the electropneumatic regulator 51 is a flow rate control valve capable of adjusting the flow rate, the structure is not particularly concerned. It is possible to use an appropriate form of valve. In addition, as long as a predetermined amount of air can be supplied to each of the first and second branch flow paths 46 and 47, these need not be provided integrally with or close to the valve main body 16, and can be arranged at any position on the pipe line. Can be provided.

  In addition, the valve body control mechanism 21 of the driving unit 12 includes a stepping motor 56 and a motor driver 57. As shown in FIGS. 2 and 3, the stepping motor 56 is mounted in the actuator 12, and its output shaft 58 is connected to the valve shaft 29. The motor driver 57 is connected to the stepping motor 56 in FIG. The valve body control mechanism 20 can control the rotation of the stepping motor 56 by controlling a motor driver 57 by a valve body control unit 59 described later, and can control the valve body 22 connected to the valve shaft 29 to a predetermined angle. ing.

The control unit means 10 in the system main body 1 includes an air control unit 55 and a valve body control unit 59, and is configured by internal components such as a CPU (not shown), an A / D converter, a D / A converter, and the like that are made of a substrate and the like. Yes. The control unit means 10, calculation function of calculating the arrival function f (x) to induce a pressure drop in the vacuum chamber 4 (hereinafter, referred to reach function operation mechanism) and, for opening and closing the on-off valve 2 in an arbitrary time width A function for calculating the opening degree value and the closing degree value when the timer 60 and the opening / closing valve 2 are opened / closed from the output of the vacuum pressure sensor 3 and the reaching function f (x) (hereinafter referred to as a valve opening degree calculating function). ).

The air control unit 55 is connected to the valve seat control mechanism 20, controls the valve opening degree of a valve body (not shown) inside the electropneumatic regulator 51 of the valve seat control mechanism 20, and air is supplied to the electropneumatic regulator 51 from the pump 52. The amount of air (air pressure) to the air flow path 40 when supplied is controlled. Thereby, the air control unit 55 adjusts the supply / stop of air to the first branch flow path 46 and the second branch flow path 47 of the driving means 12 via the valve seat control mechanism 20, or the air supply amount, The amount of movement of the seat ring 17 is controlled to control the valve opening by the seat ring 17 so that slow exhaust can be performed. In the above description, a valve having the same function as the electropneumatic regulator 51 may be provided at the position of the electropneumatic regulator 51. As this valve, for example, although not shown, there is a flow control valve having an orifice flow path.

  The valve body control unit 59 is connected to the valve body control mechanism 21, and controls the rotation of the stepping motor 56 via the motor driver 57 in the valve body control mechanism 21, thereby causing the valve body 22 to rotate at a predetermined angle via the valve shaft 29. The rotation can be controlled. The valve body control unit 59 can control the rotation of the valve body 22 with high accuracy by finely controlling the rotation direction, rotation speed, and the like of the stepping motor 56.

  In the valve body 16, air is supplied to the air flow path 40 by the valve seat control mechanism 20, the seat ring 17 is separated from the O-ring 31 of the valve body 22 by this air, and further, the valve from the state where the seat ring 17 is opened. The valve body 22 is rotated without sliding by the body control mechanism 21. Further, the valve body control mechanism 21 rotates the valve body 22 to the valve closed state, and in this state, air is supplied to the air flow path 40 by the valve seat control mechanism 20, and the urging force of the air supply 40 and the spring 42 is Thus, the seat ring 17 is brought into contact with and separated from the valve body 22 to control the flow rate (pressure) in the flow path 24. At this time, as described above, the valve seat control mechanism 20 is controlled with high accuracy by the air control unit 55 and the valve body control mechanism 21 is controlled with high accuracy.

  Further, the system main body 1 is provided with an input means 13 composed of, for example, a PC (personal computer) or the like, and a time required for reducing the pressure inside the vacuum vessel 4 to a predetermined pressure by the input means 13, so-called pressure drop. The required time T and the pressure reached by the required time T at this time, the so-called ultimate pressure P, can be input from the outside. The input means 13 is connected to the control unit means 10, and the command input command is transmitted to the drive means 12 via the control unit means 10.

Next, each function of the arrival function calculation function and the valve opening calculation function in the control unit means 10 will be described in detail.
The arrival function calculation function is a function that calculates the relationship between the passage of time from the start of control and the pressure in the vacuum container 4 as the arrival function f (x) when the vacuum pressure in the vacuum container 4 is controlled. . The arrival function f (x) is any one of the first-order, second-order, and third-order functions, and each of the arrival functions f ₁ (x), f ₂ (x), and f ₃ (x) is Since the pressure in the vacuum vessel 4 has a gradient that decreases with the passage of time from the pressure at the start of control (starting pressure), f ₁ (x) = y ₁ = −a ₁ x + b ₁ , f _{2, respectively.} (x) = y ₂ = −a ₂ x ² + b ₂ , f ₃ (x) = y ₃ = −a ₃ x ³ + b ₃ . In this formula, -a ₁ , b ₁ , -a ₂ , b ₂ , -a ₃ , b ₃ are constants, and these constants -a ₁ , b ₁ , -a ₂ , b ₂ , -a ₃ , By calculating b ₃ respectively, first, second, and third order arrival functions are obtained.

At this time, constants b ₁ , b ₂ , and b ₃ are pressures (starting pressures) at the start of control (arrival time = 0), and y ₁ , when x = 0 is substituted into each of the above functions, The values are y ₂ and y ₃ . Constants -a ₁ , -a ₂ , -a ₃ are constants b ₁ , b ₂ , b ₃ calculated from the above formula, time T required to reach the target vacuum pressure, target ultimate pressure (predetermined high (Vacuum pressure value) P is obtained by substituting the values of x and y in the above equations, respectively. As a result, first, second, and third order arrival functions f ₁ (x), f ₂ (x), and f ₃ (x) are determined.

When the arrival function f (x) is calculated, it has a calculation function that can be changed to a first, second, or third order function corresponding to the required time T to be set, and corresponds to the arrival time t. Then, an appropriate function of the first order, second order or third order function is automatically selected by the control unit means 10. FIG. 5 shows an example of the control waveform by the arrival function f (x), and FIG. 5A shows an example of the control waveform of the arrival function f ₁ (x) by the linear function. In (b), an example of the control waveform of the arrival function f ₂ (x) by a quadratic function is shown. Although an example of a control waveform by a cubic function is omitted, the arrival function f (x) is a graph in which the value of y increases with respect to the value of x as the multiplier increases, so the required time T is set short. In this case, a reaching function having a large multiplier is selected, and slow exhaust that prevents scattering of particles in a short time is possible.

  In this case, it is also possible to specify a variable order by using a command. For example, 0 to 3 are automatically selected, 0: the order is automatically selected according to the required time T, and a 1: 1 arrival function is specified. It is also possible to specify a secondary arrival function and use a command to specify a 3: 3 arrival function and input any number from the input means 13 to automatically select the order or to specify an arbitrary order.

The valve opening calculation function is a function of calculating a measured value and an arrival function by the vacuum pressure sensor 3 during a predetermined elapsed time when the pressure in the vacuum vessel 4 decreases from an atmospheric pressure or an arbitrary pressure to a target arrival pressure P. From the error with respect to the arrival function f (x) calculated from the above, the opening degree of the on-off valve 2 (open opening value) and the opening degree of the valve (closed opening value) are calculated.
Specifically, in FIG. 4, when arbitrary time when the pressure P in the vacuum vessel is decreased from P ₀ to Pn is t ₀ , t ₁ , t ₂ ,... Tn, each time t ₀ , The pressure values P ₀ , P ₁ , P ₂ ,... Pn measured by the vacuum pressure sensor 3 at t ₁ , t ₂ ,... tn are converted into theoretical pressure values p obtained based on the arrival function f (x). Based on the comparison, the opening degree value and the closing degree value of the on-off valve 2 at each time are calculated.

The open opening and the closing opening calculated by the valve opening calculation function are transmitted by instructing the opening / closing of the opening / closing valve 2 with an arbitrary time width by the timer 60, whereby the system body 1 While controlling the opening degree of 2 to prevent the particles in the vacuum vessel 4 from being rolled up, the exhaust gas is slowly exhausted so as to be reduced from the atmospheric pressure or an arbitrary pressure to a target arbitrary pressure (attainment pressure) P. At this time, the opening / closing valve 2 is instructed to open and close by the open opening value and the closed opening value calculated by the valve opening calculation function, and the occurrence of an error in the pressure value in the vacuum vessel 4 with respect to a predetermined elapsed time is prevented. It is.
At that time, when the pressure in the vacuum vessel 4 is controlled by opening / closing the open / close valve 2 to open or close, the close opening degree is increased according to the pressure drop.
In the above description, the time tn required to reach the predetermined pressure in the vacuum vessel 4 and the predetermined pressure p to be reached are input via the input means 13.

Next, in the above vacuum pressure control system, a case where a linear function (f (x) = − ax + b) is selected as a reaching function will be described as a specific example. The on-off valve 2 exhausts by slow exhaust control and process gas pressure control when exhausting from the valve open state. The slow exhaust control is to control the pressure from the initial start pressure P ₀ to the high vacuum pressure P _n , and the process gas pressure control is to control the pressure by opening and closing the valve body 22 thereafter.

As described above, in the slow exhaust control, the valve seat control mechanism 20 is controlled by the air control unit 45 to gradually release the inside of the vacuum vessel 4 closed at atmospheric pressure or an arbitrary pressure, thereby achieving a target ultimate pressure P. Slow exhaust up to. Prior to the slow exhaust, a command is input in advance from the external input means 13 to the control unit means 10 so that the control unit means 10 reaches the predetermined pressure in the vacuum vessel 4 and the predetermined pressure (attainment pressure) P at the time of arrival. To do. The arrival time T is set to a time at which generation of particles in the vacuum vessel 4 is difficult to occur when the pressure is reduced from the atmospheric pressure or an arbitrary pressure to the ultimate pressure P. The size of the vacuum vessel 4 and the wafer to be processed are set. It is set to an appropriate value according to the number and the type of material gas.
As described above, when the arrival time T, the arrival pressure P, and the start pressure in the vacuum vessel 4 are determined, the arrival function calculation function sets the arrival time to x, the arrival pressure to y, and the start pressure to b. A constant a is obtained by substituting into the function y = −ax + b, and this result is substituted into the linear function to determine the reaching function f (x).

  Subsequently, based on the arrival function f (x), the opening degree value and the closing degree value are calculated by the valve opening degree calculation function, and the closed state of the electromagnetic valve 50 is maintained as shown in FIG. While being done, the opening degree of the seat ring 17 is controlled by controlling the valve opening degree of the electropneumatic regulator 51 by the air control unit 55. The air supply pressure to the air flow path 40 is adjusted by the control of the electropneumatic regulator 51, and the amount of movement of the opening degree and the closing degree of the seat ring 17 with respect to the valve body 22 is finely controlled. 22 is controlled. Further, by gradually increasing the closing opening according to the pressure drop in the vacuum vessel 4, it is possible to reduce the contact frequency of the O-ring 31 that contacts the seat ring 17 and extend the life of the O-ring 31. .

  Subsequently, at the time of slow exhaust, the opening degree and the closing degree are calculated by the valve opening degree calculation function with respect to the arrival function f (x) that prevents the generation of particles obtained by the arrival function calculation function. Depending on the result, the flow rate is controlled by opening and closing the on-off valve 2 with an arbitrary time width by the timer 60, and the actual pressure is brought close to the ultimate pressure P in the elapsed time.

For example, in the valve opening calculation function of FIG. 4, when the control at each time is set to step 0, step 1, step 2,..., Step N, the control unit means 10 performs the reaching function f (x) at each step. The pressure in the vacuum vessel 4 is controlled by shifting the opening degree gradually and increasing the opening degree while changing the opening degree and the closing degree so as to approach each other. Further, the control in each step will be described in detail. The initial pressure measured by the vacuum pressure sensor 3 in step 0 at the start of operation is P ₀ , the open opening is the start opening EvSt, and the close opening is the minimum opening EvCls. Then, the opening / closing valve 2 starts repeating the opening / closing operation while gradually increasing the closing opening as described above.

In step 1, the pressure P ₁ is measured by the vacuum pressure sensor 3, and the pressure gradient (not shown) A ₁ (= −pressure P ₁ / pressure P ₀ when the control unit means 10 reaches t ₁ from the arrival time t ₀ is reached. ) And the slope A ₁ of the pressure is compared with the slope a of the arrival function f (x) calculated by the arrival function calculation function, and the pressure P ₁ and the arrival function f (x) are calculated. Calculates the deviation from the calculated pressure p _{1 (} not shown), the opening correction value of the starting opening, the closing minimum opening, the opening opening value, and the closing opening value, and based on these calculation results, the air control The on-off valve 2 is subjected to slow exhaust control by the unit 55 so that the pressure gradient A ₁ and the arrival function gradient a, the measured pressure P ₁ and the calculated pressure p ₁ are brought closer in the next step (step 2).

Subsequently, in step 2, as in step 1, the vacuum pressure sensor 3 measures the pressure P _2, the pressure of the arrival function f (x) when it reaches the elapsed time t ₂ from the elapsed time t ₁ Slope A ₂ (= −pressure P ₂ / pressure P ₁ ), the pressure slope A ₂ is compared with the slope a of the arrival function f (x), and the value of the pressure P ₂ and the arrival function f are compared. and divergence between the calculated pressure p ₂ calculated in (x), starting opening, opening correction value of the closing minimum opening, open opening value, calculates the closed opening value, based on these calculation results Further, the on-off valve 2 is subjected to slow exhaust control so that the pressure gradient A ₂ and the arrival function gradient a, the measured pressure P ₂ and the calculated pressure p ₂ are brought closer in the next step (step 3).

  Thereafter, the control up to Step N is performed in the same manner. When the pressure in the vacuum container 4 reaches the ultimate pressure P in Step N, the seat ring 17 is fully opened, and the air control unit 55 of the control unit means 10. This completes the slow exhaust control of the seat ring 17. When the slow exhaust by the air control unit 55 is finished, the electropneumatic regulator 51 is closed, and at the same time, the electromagnetic valve 50 is controlled to be opened so that air is supplied to the air flow path 40 and the seat ring 17 is completely closed. Will be open.

  Subsequently, the control of the valve seat control mechanism 20 by the air control unit 55 is switched to the control of the valve body control mechanism 21 by the valve body control unit 59. As shown in FIG. 7, the valve body 22 of the on-off valve 2 is controlled to open and close by the valve body control unit 59 being rotationally controlled by the stepping motor 56 of the valve body control mechanism 21. The process gas pressure in the vacuum vessel 4 is controlled to the pressure.

  In the above description, the case where the vacuum pressure control system is controlled using the arrival function f (x) as a linear function has been described, but the arrival function f (x) may be a quadratic function or a cubic function. Can be controlled. The arrival function f (x) is appropriately varied by the arrival function calculation function according to the length of the required pressure drop time T to be set, and an optimum multiplier function is selected. Regardless of the function, by finely setting the steps at the time of control, the pressure can be controlled by repeating the open / close operation finely for each step until the ultimate pressure P is reached from the starting pressure. Thus, it is possible to control with high accuracy while reducing the error of the measurement pressure with respect to the arrival function f (x).

  Here, for example, in FIG. 6, the solid line shows a curve of a function when the pressure is controlled by the above-described vacuum pressure control. In this case, since the number of steps by the valve opening value calculation function can be increased and the curve can be brought close to the curve of the reaching function f (x), the pressure can be controlled more accurately. On the other hand, the broken line in the figure shows a graph when the pressure is controlled according to Patent Document 1. In this case, as shown in the figure, it is necessary to set a target vacuum pressure change point and a target vacuum pressure change speed that are set in advance, and the set number (point A, point B, point C) is set in this way. When the number is small, the graph is separated from the ideal reaching function. For this reason, it is necessary to increase the number of set points, and as a result, the trouble of obtaining each set value in advance increases. In the above-described vacuum pressure control system of the present invention, it is only necessary to input a command for the required time T and the ultimate pressure P, so that no labor is required.

  As described above, the vacuum pressure control system of the present invention includes the control unit means 10 having the reaching function calculation function, the timer 60, and the valve opening calculation function, the drive means 12, and the input means 13. Since the pressure is reduced from the atmospheric pressure or an arbitrary pressure to the target arbitrary pressure, there is no need to obtain a set value in advance by calculation, and a desired required time T and ultimate pressure P are input. It is possible to control the pressure easily and accurately while suppressing scattering of particles from atmospheric pressure or low vacuum close to atmospheric pressure to high vacuum.

  In addition, since the valve seat control mechanism 20 is slow exhaust controlled by the air control unit 55, the pressure can be controlled with higher accuracy. Further, after the slow exhaust, the valve body control mechanism 20 is controlled by the valve body control unit 59 to process gas pressure. Since the flow rate is controlled, the flow rate can be accurately controlled from a minute flow rate to a large flow rate. In this case, in particular, pressure control can be performed with high accuracy at a minute flow rate, and particle scattering during slow exhaust can be reliably suppressed.

  When the valve main body 16 is again fully closed from the motor control state, the valve body 22 is rotated to the fully closed position, and the air is exhausted from the air flow path 40 with the solenoid valve 50 turned OFF. 42 presses the seat ring 17 against the O-ring 31 to seal it, and the flow path 24 is closed.

  Furthermore, by using the high-speed air control flow path 70 shown in FIG. 8, the valve main body 16 can be shut off at high speed in the valve closed state. In the drawing, an electropneumatic regulator 71, a three-way solenoid valve 72, a pressure switch 73, and a two-way air valve 74 are provided in the air shut-off channel 70. This air control channel 70 is a cylinder of the body 23 in FIG. It is connected to an air flow path 40 that continues from a certain mounting recess 36.

  The air control flow path 70 is provided in parallel by an air supply side flow path 75 and an air exhaust side flow path 76, and a first bypass is provided between the air supply side flow path 75 and the air exhaust side flow path 76. A flow path 77 and a second bypass flow path 78 are provided. In the air supply side flow path 75, an electropneumatic regulator 71, a three-way solenoid valve 72, and a pressure switch 73 are arranged in series in this order from the cylinder 36 side. A direction air valve 74 is provided.

  The electropneumatic regulator 71 is provided at a position connecting the air supply side flow path 75 and the first bypass flow path 77, can adjust the flow rate of air supplied from the air supply side flow path 75 into the cylinder 36, and The exhaust air from the cylinder 36 can be flowed to the air exhaust side flow path 76 via the first bypass flow path 77. The three-way solenoid valve 72 is provided at a position where the air supply side flow path 75 and the first bypass flow path 77 are connected, and supplies supply air to the cylinder 36 side or exhaust air from the cylinder 36, The flow can be switched to flow to the air exhaust side flow path 76 via the second bypass flow path 78. The pressure switch 73 is provided to sense the pressure in the air supply side flow path 75.

  The two-way air valve 74 is provided in the air exhaust side flow path 76, and a third bypass flow path 79 is connected to the two-way air valve 74 from the air supply side flow path 75. The two-way air valve 74 is a normally open type valve, and is normally configured to be able to exhaust air from the cylinder 36. On the other hand, when air is supplied from the air supply side passage 75, a third bypass is provided. Air is supplied through the flow path 79 so that the valve is closed.

  In the air control flow path 70, when the three-way solenoid valve 72 is opened and air is supplied, the air flows into the two-way air valve 74 via the third bypass flow path 79, and the two-way air valve 74 is closed. Thus, the exhaust from the cylinder 36 is prevented. In this state, for example, when an input signal of 0 to 5 V is input to the electropneumatic regulator 71, the operation pressure from the supply side is output in a magnitude of 0 to 0.5 MPa in proportion to the input signal. With this operating pressure, a seat ring (not shown) in the cylinder 36 is reciprocated by a stroke of, for example, 0 to 2.5 mm in proportion to the output pressure of the electropneumatic regulator 71 to open and close the valve body 16.

  When shutting off the valve body 16 in the closed state, the exhaust air from the cylinder 36 flows into the second bypass flow path 78 and is exhausted by switching the three-way solenoid valve 72, and the air to the air supply side flow path 75 is exhausted. Supply is also stopped. At this time, when the input signal to the electropneumatic regulator 71 is exhausted to 0 V, it takes about 1.5 seconds for the cylinder 36 to close the valve in a normal circuit. When the two-way air valve 74 of the air exhaust side flow path 76 piped in parallel with the air supply side flow path 75 is opened, the exhaust air flows into the two-way air valve 74 and the electropneumatic regulator 71 / 3-way solenoid valve 72. Since the air is exhausted from the air exhaust side flow path 76, the air can be interrupted at a high speed of 1 second or less, and the interruption time can be greatly shortened.

DESCRIPTION OF SYMBOLS 1 System main body 2 On-off valve 3 Vacuum pressure sensor 4 Vacuum container 5 Vacuum pump 10 Control unit means 12 Drive means 60 Timer 61 Input means f (x) Arrival function P Ultimate pressure T Time required

Claims (1)

An opening / closing valve that is provided in the middle of connecting a vacuum pump to the vacuum vessel and that changes the vacuum pressure in the vacuum vessel , and an opening degree of the opening / closing valve via a vacuum pressure sensor that measures the vacuum pressure in the vacuum vessel A vacuum pressure control system for controlling a calculation function for calculating a reaching function for inducing a pressure drop in the vacuum vessel, and a timer for controlling the opening / closing of the opening / closing valve at an arbitrary time width, A function of calculating an opening degree value that is an opening degree when the on-off valve is opened and a closing degree value that is an opening degree when the on- off valve is closed from the output of the vacuum pressure sensor and the reaching function the preparative and control unit means having said open opening value and a valve control mechanism for the seat ring and a valve seat the valve seat controlling mechanism for operating a and operating the valve body of the closing valve of the on-off valve and closed opening value A drive means that moves, and an input means for inputting a required time for pressure drop and an ultimate pressure from the outside are provided to reduce the pressure from atmospheric pressure or any pressure to any target pressure. To vacuum pressure control system.

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