Vacuum pressure control system

Abstract

To detect damage to a bellowsphragm used with a vacuum on-off valve.SOLUTION: A vacuum on-off valve 30 includes a driving section 31 that applies driving force to a valve element 40 on the basis of an opening command value. The driving section 31 includes: a driving shaft 39 coupled to the valve element 40; a piston 34 coupled to a side opposite to the valve element 40 of the driving shaft 39; a cylinder 33 having a piston chamber 331 that accommodates the piston 34; and a bellowsphragm 38 held by the piston 34 and defining the piston chamber 331. A control device 70 includes an abnormality detection program 702a which calculates an opening difference indicating a difference between the opening command value output to the vacuum on-off valve 30 and an actual opening, which is an actual opening of the valve element 40 driven on the basis of the opening command value, and determines that the bellowsphragm 38 has been damaged when the opening difference is equal to a first predetermined threshold value or larger.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a vacuum pressure control system that is disposed between a vacuum chamber and a vacuum pump for evacuating the vacuum chamber and that controls the pressure value of the vacuum chamber by adjusting the opening of a valve body, and that outputs an opening command value to the vacuum opening / closing valve to indicate the opening required to adjust the pressure value to a target value. [Background technology]

[0002] Conventionally, in a film formation process in a semiconductor manufacturing process, a vacuum chamber is depressurized by a vacuum pump, and a process gas is supplied onto a wafer fixed in the vacuum chamber. At this time, a vacuum pressure control system is used to adjust and maintain the pressure value in the vacuum chamber at a pressure value suitable for the film formation conditions. The vacuum pressure control system includes, for example, a vacuum on-off valve disposed between the vacuum chamber and the vacuum pump, and a control device for controlling the vacuum on-off valve.

[0003] The vacuum on-off valve includes a valve body and a valve seat against which the valve body comes into contact and separates, and the distance of the valve body from the valve seat (i.e., the opening degree) is adjustable. The vacuum on-off valve also includes a drive unit that applies a driving force to the valve body. The drive unit is an air cylinder that operates by air pressure, and includes a drive shaft that is connected to the valve body, a piston that is connected to the drive shaft on the opposite side to the valve body, a cylinder with a piston chamber that houses the piston, a thin-film bellofram that is held by the piston and defines the piston chamber, and a compression coil spring that biases the piston in a valve closing direction. The piston is slidable in a valve opening direction and a valve closing direction within the piston chamber, and when compressed air is supplied to the drive unit, the piston moves in the valve opening direction, thereby separating the valve body from the valve seat. On the other hand, when the supply of compressed air is stopped, the piston moves in the valve closing direction due to the compression coil spring, thereby causing the valve body to come into contact with the valve seat.

[0004] The control device outputs an opening command value to the vacuum on-off valve. This opening command value instructs the vacuum on-off valve on the opening degree of the vacuum on-off valve required to adjust the pressure value of the vacuum chamber to a target value. The vacuum on-off valve receives this output of the opening command value and adjusts the opening degree according to the opening command value. Note that, for example, the system disclosed in Patent Document 1 is known as a vacuum pressure control system as described above. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-093055 Summary of the Invention [Problem to be solved by the invention]

[0006] The bellofram provided in the actuator of the vacuum on-off valve is folded back deeply inside the cylinder and deforms as the piston moves. During this process, friction between the bellofram and the piston, and friction between the bellofram pieces at the folded back portion can occur, so there is a risk of the bellofram being damaged, such as being torn, by repeated operation of the actuator.

[0007] If the bellofram breaks, the piston chamber will no longer be airtight, the operating air will leak, and the piston will no longer move accurately. In other words, the opening will no longer be accurately in accordance with the opening command value. This will make it impossible to control the pressure value of the vacuum chamber to the target value, which could lead to defective semiconductor manufacturing.

[0008] The present invention has been made in consideration of the above problems, and has an object to provide a vacuum pressure control system capable of detecting damage to a bellofram used in a vacuum on-off valve. [Means for solving the problem]

[0009] In order to solve the above problems, a vacuum pressure control system according to one aspect of the present invention has the following configuration.

[0010] (1) A vacuum pressure control system comprising a vacuum on-off valve disposed between a vacuum chamber and a vacuum pump for evacuating the vacuum chamber, the vacuum on-off valve controlling the pressure value of the vacuum chamber by adjusting the opening of a valve body, and a control device outputting an opening command value to the vacuum on-off valve to indicate the opening required to adjust the pressure value to a target value, the vacuum on-off valve comprising a drive unit that applies a driving force to the valve body based on the opening command value, the drive unit comprising a drive shaft connected to the valve body, a piston connected to the side of the drive shaft opposite the valve body, a cylinder having a piston chamber that houses the piston, and a bellofram held by the piston to partition the piston chamber, the control device comprising an abnormality detection program that calculates an opening difference, which is the difference between the opening command value output to the vacuum on-off valve and an actual opening, which is the actual opening of the valve body driven by the opening command value, and determines that the bellofram is damaged when the opening difference is equal to or greater than a first predetermined threshold value. Damage to the bellofram referred to here means, for example, a state in which the bellofram is torn and the airtightness of the piston chamber can no longer be maintained.

[0011] The inventors of the present application have focused on the fact that when the bellofram is damaged and the piston chamber cannot be kept airtight, the piston does not operate sufficiently and the actual opening becomes smaller than the target opening (the opening indicated by the opening command value). As a result, it has been confirmed through experiments that it is possible to determine whether the bellofram is damaged by calculating the opening difference, which is the difference between the opening command value and the actual opening, and monitoring the opening difference. More specifically, it is possible to determine that the bellofram is damaged when the opening difference is equal to or greater than a predetermined threshold value. Therefore, according to the vacuum pressure control system described in (1), the control device is characterized by being provided with an abnormality detection program that calculates the opening difference, which is the difference between the opening command value output to the vacuum on-off valve and the actual opening, which is the actual opening of the valve body driven by the opening command value, and determines that the bellofram is damaged when the opening difference is equal to or greater than a first predetermined threshold value, so that it is possible to detect damage to the bellofram used in the vacuum on-off valve.

[0012] (2) In the vacuum pressure control system described in (1), it is preferable that the first predetermined threshold value is set between 0.5% and 2.0%.

[0013] The inventors of the present application confirmed through experiments that it is possible to more reliably detect damage to bellofram by setting the first predetermined threshold value between 0.5% and 2.0% inclusive. This is because if the first predetermined threshold value is set to a value smaller than 0.5%, there will be many false positives, and if the first predetermined threshold value is set to a value larger than 2.0%, damage to bellofram cannot be detected quickly.

[0014] (3) In the vacuum pressure control system described in (1) or (2), it is preferable that the abnormality detection program performs the calculation at one-second intervals and determines that the bellofram is damaged when the opening difference is greater than or equal to the first predetermined threshold value three or more times in succession.

[0015] In a vacuum on-off valve, the difference between the opening command value and the actual opening may suddenly become large due to hunting, which is a phenomenon in which the opening of the valve body changes oscillatingly. For this reason, if it were to be determined that the Bellofram is damaged every time the opening difference is equal to or greater than the first predetermined threshold, there is a risk of falsely detecting that the Bellofram is damaged even when the Bellofram is not damaged. According to the vacuum pressure control system described in (3), the opening command and actual opening are compared at one-second intervals, and the Bellofram is determined to be damaged when the difference is equal to or greater than the first predetermined threshold three or more times in succession, thereby preventing false detection. The reason for the phrase "three or more times in succession" is that there is a risk of false detection due to hunting if it is compared two times in succession.

[0016] (4) In the vacuum pressure control system described in any one of (1) to (3), it is preferable that the abnormality detection program performs the calculation when the pressure value of the vacuum chamber exceeds a second predetermined threshold value.

[0017] (5) In the vacuum pressure control system described in (4), it is preferable that the second predetermined threshold value is the target value plus a value that is 0.2% to 1% of the target value.

[0018] In a vacuum on-off valve, the difference between the opening command value and the actual opening may suddenly become large due to hunting, which is a vibrational change in the opening of the valve body. For this reason, if it is determined that the bellofram is damaged in all cases where the opening difference is equal to or greater than the first predetermined threshold, there is a risk of falsely detecting that the bellofram is damaged even when the bellofram is not actually damaged. Therefore, the inventors of the present application have focused on the fact that when the bellofram is damaged and the actual opening becomes smaller than the target opening (the opening specified by the opening command value), the vacuum chamber is not sufficiently evacuated, so the pressure value of the vacuum chamber increases over time, and have confirmed through experiments that it is possible to prevent false detection by starting calculation of the opening difference when the pressure value of the vacuum chamber exceeds a second predetermined threshold. The second predetermined threshold is, for example, a value obtained by adding a value of 0.2% to 1% of the target value to the target value. The reason for specifying "0.2% or more and 1% or less" is that if the threshold value is set to a value that is less than 0.2% of the target value plus the target value, it is not possible to reliably prevent false positives, and if the threshold value is set to a value that is more than 1% of the target value plus the target value, damage to the bellofram cannot be detected quickly. Effect of the Invention

[0019] According to the vacuum pressure control system of the present invention, it is possible to detect damage to the bellofram used in the vacuum on-off valve. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a semiconductor manufacturing apparatus for performing a film forming process on a wafer. [Diagram 2] FIG. 2 is a cross-sectional view of the vacuum on-off valve, showing a state in which the valve body is at its maximum opening degree. [Diagram 3] 2 is a block diagram showing the configuration of a control device used in the vacuum pressure control system according to the present embodiment. FIG. [Figure 4]Fig. 4(a) is a graph showing the relationship between time and the opening command value output by the control device, Fig. 4(b) is a graph showing the relationship between time and the actual opening of the vacuum on-off valve (valve body), and Fig. 4(c) is a graph showing the relationship between time and the pressure value of the vacuum chamber. [Diagram 5] 13 is a flowchart showing the operation of an anomaly detection program. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] An embodiment of a vacuum pressure control system 1 according to the present invention will be described in detail with reference to the drawings. Note that the drawings used in the description are simplified for the purpose of explanation and do not accurately represent shapes, dimensions, etc.

[0022] (About the configuration of semiconductor manufacturing equipment) The configuration of a vacuum pressure control system 1 according to this embodiment will be described with reference to the drawings. Fig. 1 is a diagram illustrating a schematic configuration of a semiconductor manufacturing apparatus 100 for performing a film forming process on a wafer 150. The semiconductor manufacturing apparatus 100 is an apparatus for forming a thin film on the surface of the wafer 150 by using, for example, atomic layer deposition (ALD).

[0023] The semiconductor manufacturing apparatus 100 mainly includes a gas supply source 16 which is a supply source of a process gas for performing surface treatment on a wafer 150, an N2 supply source 17 which is a supply source of nitrogen gas (N2) used to purge the process gas from a vacuum chamber 11, a mass flow controller 20 which controls the flow rate of the process gas or the process gas, a vacuum chamber 11 which is a vacuum container, a vacuum pump 15 which evacuates the vacuum chamber, and a vacuum pressure control system 1 which controls the pressure value within the vacuum chamber 11. Furthermore, the vacuum pressure control system 1 mainly includes a vacuum on-off valve 30, a pressure sensor 12 which detects the pressure value of the vacuum chamber 11, and a control device 70 which controls the vacuum on-off valve 30.

[0024] 1, a gas supply source 16, a mass flow controller 20, a vacuum chamber 11, a vacuum on-off valve 30, and a vacuum pump 15 are connected in series from the upstream side. An N2 supply source 17 is connected in parallel to the gas supply source 16 on the upstream side of the mass flow controller 20. A pressure sensor 12 is located between the vacuum chamber 11 and the vacuum on-off valve 30 via a shutoff valve 13. A control device 70 is electrically connected to the pressure sensor 12 and the vacuum on-off valve 30.

[0025] A process gas supplied from a gas supply source 16 or a purge gas supplied from an N2 supply source 17 is supplied to the vacuum chamber 11 through a gas inlet 11a after being adjusted to a predetermined flow rate by a mass flow controller 20. The predetermined flow rate of the process gas is a flow rate when the pressure of the vacuum chamber 11 is actually controlled, and refers to a flow rate of the process gas required for forming a film on the wafer 150. A first port 41a of a vacuum on-off valve 30 is connected to a gas exhaust port 11b of the vacuum chamber 11 through a pipe, and a second port 41b of the vacuum on-off valve 30 is connected to a vacuum pump 15 through a pipe, so that the process gas or purge gas supplied to the vacuum chamber 11 can be sucked by the vacuum pump 15.

[0026] At this time, the control device 70 adjusts the opening of the vacuum on-off valve 30 so that the pressure value in the vacuum chamber 11 becomes the target value while monitoring the pressure value in the vacuum chamber 11 from the pressure sensor 12. More specifically, the control device 70 outputs an opening command value to the vacuum on-off valve for instructing the opening of the vacuum on-off valve required to adjust the pressure value to the target value. Then, the vacuum on-off valve adjusts the opening of the valve body based on the opening command value, thereby adjusting the pressure value in the vacuum chamber 11 to the target value.

[0027] (Configuration of vacuum on-off valve) 2 is a cross-sectional view of the vacuum on-off valve 30, showing the state in which the valve element is at its maximum opening degree. As shown in FIG. 2, the vacuum on-off valve 30 includes a drive unit 31 and a valve unit 32, which are assembled to each other above and below in the figure.

[0028] The main components of the drive unit 31 are a cylinder 33, a piston 34, a bellofram 38, and a drive shaft 39. The cylinder 33 is a hollow case, and has a piston chamber 331 therein as a substantially cylindrical space. The piston 34 is housed in the piston chamber 331 so as to be slidable in a direction parallel to the direction in which the drive unit 31 and the valve unit 32 are stacked (the up-down direction in the figure).

[0029] A slide lever 36 is fixed to the end face of the piston 34 opposite to the drive unit 31 (the upper end face in the figure). A potentiometer 37 is attached to the outside of the cylinder 33 as an opening sensor. The potentiometer 37 incorporates a variable resistor (not shown) connected to the slide lever 36. As the slide lever 36 moves up and down integrally with the piston 34, the value of the variable resistor changes, and the potentiometer 37 outputs the resistance value to the control device 70 as a value correlating with the position of the piston 34 in the vertical direction. This allows the control device 70 to monitor the opening of the vacuum on-off valve 30, and adjusts the opening command value output to the vacuum on-off valve 30 while monitoring the opening of the vacuum on-off valve 30.

[0030] Bellofram 38 is fixed to the end face (lower end face in the figure) of piston 34 on the opposite side to drive unit 31. Bellofram 38 is a cylindrical diaphragm with a bottom, which is made by integrally molding a base fabric such as polyester, polyamide, aramid, etc. with fluororubber (e.g. FKM, etc.). The center of this Bellofram 38 is fixed to the lower end face of piston 34. In addition, this Bellofram 38 has an outer periphery fixed to cylinder 33, and has a folded portion 38a that is folded back deeply in the upward direction in FIG. 2 between the outer periphery of piston 34 and the inner periphery of piston chamber 331. The Bellofram 38 as described above is deformable by following the sliding of piston 34 in the up-down direction in the figure. During this deformation, friction between Bellofram 38 and piston 34 and friction between Bellofram 38 at the folded portion 38a may occur. For this reason, repeated deformation may cause damage such as tearing of Bellofram 38. In particular, folded-back portion 38a is thinner than other portions, at only a few millimeters, and is therefore more susceptible to damage. The occurrence of such damage can be detected by an abnormality detection program 702a, which will be described later.

[0031] The piston chamber 331 is divided by the bellofram 38 into a pressurized chamber 331b on the valve portion 32 side and an atmospheric chamber 331a on the opposite side. Atmosphere can be introduced into the atmospheric chamber 331a through an atmospheric port (not shown). A return spring 35 is housed in the atmospheric chamber 331a, and the piston 34 is biased toward the valve portion 32 side (the lower side in the figure) by the return spring 35. Compressed air can be introduced into the pressurized chamber 33b from an air supply source (not shown) through a pressurized port (not shown). When compressed air is introduced into the pressurized chamber 33b, the bellofram 38 is pressurized, and the piston 34 slides toward the atmospheric chamber 331a. The bellofram 38 is designed to maintain an effective pressure-receiving area by compressed air constant and unchanged.

[0032] A drive shaft 39 is connected to the center of the piston 34, and is inserted into the valve section 32. The valve section 32 includes the drive shaft 39, a valve body 40, and a casing 41 that houses the drive shaft 39 and the valve body 40. The valve body 40 is connected to the end of the drive shaft 39 opposite to the end to which the piston 34 is connected, i.e., the end inserted into the valve section 32. The casing 41 is cylindrical, and has the first port 41a and second port 41b described above. A bellows 42 is provided on the upper surface of the valve body 40. The bellows 42 is arranged in a state in which it contains the drive shaft 39.

[0033] An O-ring 43 is attached to the lower surface of the valve element 40. A valve seat 45 against which the valve element 40 comes into contact and separates is provided on the inner wall of the casing 41, on the outer circumferential side of the first port 41a. When the valve element 40 moves toward the valve seat 45 and comes into contact with the valve seat 45, and the O-ring 43 is pressed against the valve element 40 and the valve seat 45, that is, when the vacuum on-off valve 30 is in a fully closed state, the flow of the process gas is shut off.

[0034] Furthermore, as the piston 34 moves up and down, the valve element 40 moves up and down via the drive shaft 39. This changes the opening degree of the vacuum on-off valve 30. The potentiometer 37 measures the vertical position of the piston 34, and therefore the vertical position of the valve element 40, i.e., the opening degree of the vacuum on-off valve 30, and outputs the measurement value to the control device 70.

[0035] (Regarding the control device) Fig. 3 is a block diagram showing the configuration of the control device 70 used in the vacuum pressure control system 1 according to this embodiment. As shown in Fig. 3, the control device 70 includes a CPU 701, a ROM 702, a RAM 703, and a storage unit 704. An abnormality detection program 702a for detecting an abnormality in the vacuum on-off valve 30 is stored in the ROM 702. The CPU 701 controls the operation of the vacuum on-off valve 30 according to the abnormality detection program 702a while temporarily storing data in the RAM 703. In addition, the storage unit 704 can store the operation history, operation results, etc. of the abnormality detection program 702a.

[0036] (Vacuum pressure control system operation) Here, the control of the pressure value of the vacuum chamber 11 by the vacuum pressure control system 1 will be described with reference to FIG. 4. FIG. 4(a) is a graph showing the relationship between time and the opening command value output by the control device 70. FIG. 4(b) is a graph showing the relationship between time and the actual opening of the vacuum on-off valve 30 (valve element 40). The actual opening is the actual opening of the valve element driven by the opening command value. FIG. 4(c) is a graph showing the relationship between time and the pressure value of the vacuum chamber 11. The opening command value and the actual opening are expressed as values ​​from 0 to 100, with the fully closed position of the valve element 40 being 0% and the fully open position being 100%. In addition, in the graphs shown in FIGS. 4(a), (b), and (c), the waveforms shown by solid lines show the operation when the bellofram 38 is damaged, and the waveforms shown by dashed lines show normal operation. Damage to bellofram 38 referred to here means a state in which the bellofram is torn and the airtightness of pressurized chamber 331b can no longer be maintained.

[0037] In this embodiment, the target value of the pressure value of the vacuum chamber 11 is set to a pressure value P11. The opening degree of the vacuum on-off valve 30 required to obtain this pressure value P11 is set to an opening degree V11, and the opening degree command value output by the control device 70 to obtain the opening degree V11 is set to a command value C11.

[0038] First, normal operation, shown by the dashed waveforms in FIGS. 4(a), (b), and (c), will be described.

[0039] In order to set the pressure value of the vacuum chamber 11 to the target pressure value P11, the control device 70 first starts outputting the command value C11 (time t0). This starts the supply of compressed air to the pressurizing chamber 331b, and the valve body 40 of the vacuum on-off valve 30 starts operating with a slight delay from the output of the command value C11. That is, the actual opening starts to fluctuate (time t1). Accordingly, the pressure value also starts to fluctuate. Then, when the actual opening reaches the opening V11 corresponding to the command value C11 (time t3), the pressure value of the vacuum chamber 11 reaches the target pressure value P11. Note that in FIG. 4, the pressure value reaches the pressure value P11 at the same time as the actual opening reaches the opening V11 at time t3, but this is not necessarily simultaneous, and the pressure value P11 may be reached with a delay after the actual opening reaches the opening V11. Then, after time t3, the command value C11 continues to be output, so that the actual opening is maintained at the opening V11 and the pressure value of the vacuum chamber 11 is maintained at the target pressure value P11.

[0040] Next, the operation when the bellofram 38 is damaged, as shown by the solid line waveforms in FIGS. 4(a), (b) and (c), will be described.

[0041] In order to set the pressure value of the vacuum chamber 11 to the target pressure value P11, the control device 70 first starts outputting the command value C11 (time t0). This starts the supply of compressed air to the pressurizing chamber 331b, and the valve body 40 of the vacuum on-off valve 30 starts operating with a slight delay from the output of the command value C11. That is, the actual opening starts to fluctuate (time t1). However, if the bellofram 38 is damaged, compressed air leaks from the pressurizing chamber 331b to the atmospheric chamber 331a, so that the piston 34 does not operate sufficiently and the actual opening remains at the opening V21, which is smaller than the target opening V11 (see FIG. 4(b)). Then, if the opening of the vacuum on-off valve 30 is smaller than the target, the opening command value is increased over time to obtain the opening V11 (see FIG. 4(a)). Furthermore, if the opening of the vacuum on-off valve 30 is smaller than the target, the vacuum chamber 11 is not sufficiently evacuated, and the pressure value of the vacuum chamber 11 increases over time (see FIG. 4(c)).

[0042] (About the anomaly detection program) Based on the behavior of the graph in Fig. 4 as described above, the anomaly detection program 702a can detect that the bellofram 38 has been damaged. Fig. 5 is a flowchart showing the operation of the anomaly detection program 702a. Specifically, the detection is performed as follows.

[0043] When the pressure control system 1 starts the pressure control of the vacuum chamber 11, the abnormality detection program 702a starts operating. When the abnormality detection program 702a starts operating, the control device 70 monitors the pressure value in the vacuum chamber 11 by the pressure sensor 12 (S1 in FIG. 5). Then, unless the pressure value in the vacuum chamber 11 exceeds a predetermined threshold value (a second predetermined threshold value) (S1 in FIG. 5: NO), the control device 70 continues the feedback control of the vacuum on-off valve 30 (S3).

[0044] When the pressure value in the vacuum chamber 11 exceeds a predetermined threshold value (second predetermined threshold value) (S1 in FIG. 5: YES), the control device 70 checks the actual opening degree of the vacuum on-off valve 30 by the potentiometer 37 (S4 in FIG. 5). The above-mentioned predetermined threshold value is preferably a value obtained by adding a value of 0.2% to 1% of the target value to the target value of the pressure value in the vacuum chamber 11, and in this embodiment, it is set to a value obtained by adding a value of 0.2% of the target value to the target value. That is, the pressure value P21, which is a value obtained by adding a value of 0.2% of the pressure value P11 to the pressure value P11, is set to the threshold value. That is, when the pressure value in the vacuum chamber 11 reaches the pressure value P21, the control device 70 checks the actual opening degree of the vacuum on-off valve 30 by the potentiometer 37 (time point t4 in FIG. 4).

[0045] Next, the control device 70 calculates an opening difference, which is the difference between the opening command value outputted by the control device 70 to the vacuum on-off valve 30 and the actual opening (the value confirmed in S4), which is the actual opening of the valve element 40 driven by the opening command value, and monitors the opening difference (S5 in FIG. 5). This calculation is performed at intervals of one second (for example, at times t4, t5, t6, etc. in FIG. 4). Specifically, at time t4, the difference between the opening command value C21 at time t4 and the opening V21 at time t4 is calculated, at time t5, the difference between the opening command value C22 at time t5 and the opening V21 at time t5 is calculated, and at time t6, the difference between the opening command value C23 at time t6 and the opening V21 at time t6 is calculated. Also, to give a numerical example, if the opening command value indicates an opening of 7% and the actual opening is 3%, the opening difference is 4%.

[0046] Then, when the opening difference calculated at one second intervals as described above is equal to or greater than the threshold value of 1% (an example of the first predetermined threshold value) three times in a row (S5 in FIG. 5: YES), it is determined that the bellofram 38 of the vacuum on-off valve 30 is damaged, and an alarm is issued (S6 in FIG. 5). Specifically, when the opening difference calculated at time t4 is equal to or greater than 1%, the opening difference calculated at time t5 is equal to or greater than 1%, and the opening difference calculated at time t6 is equal to or greater than 1%, it is determined that the bellofram 38 of the vacuum on-off valve 30 is damaged. Also, to give a numerical example, for example, if the opening command value indicates an opening of 7% and the actual opening is 3%, the opening difference is 4%, and therefore it is determined that the opening difference is 1% or greater. In this way, when an opening difference of 1% or greater is calculated three times in a row, it is determined that the bellofram 38 is damaged, and an alarm is issued. It is preferable to set the above threshold value between 0.5% and 2.0%, and 1% is just an example.

[0047] On the other hand, unless the opening difference calculated at one-second intervals is 1% or more three consecutive times (S5 in FIG. 5: NO), the control device 70 continues the feedback control of the vacuum on-off valve 30 (S3).

[0048] (About the action and effect) As described above, the vacuum pressure control system 1 according to this embodiment has the following features: (1) In a vacuum pressure control system 1 including a vacuum on-off valve 30 that is disposed between a vacuum chamber 11 and a vacuum pump 15 for evacuating the vacuum chamber 11 and controls the pressure value of the vacuum chamber 11 by adjusting the opening of a valve element 40, and a control device 70 that outputs an opening command value to the vacuum on-off valve for instructing the opening required to adjust the pressure value to a target value, the vacuum on-off valve 30 includes a drive unit 31 that applies a driving force to the valve element 40 based on the opening command value, the drive unit 31 includes a drive shaft 39 connected to the valve element 40, and a drive shaft The vacuum on-off valve 30 includes a piston 34 connected to the side opposite to the valve element 40 of the vacuum on-off valve 39, a cylinder 33 having a piston chamber 331 that houses the piston 34, and a bellofram 38 that is held by the piston 34 and defines the piston chamber 331, and the control device 70 includes an abnormality detection program 702a that calculates an opening difference that is the difference between an opening command value output to the vacuum on-off valve 30 and an actual opening that is the actual opening of the valve element 40 driven by the opening command value, and determines that the bellofram 38 is damaged when the opening difference is equal to or greater than a first predetermined threshold value. Note that damage to the bellofram 38 here refers to a state in which, for example, the bellofram 38 is torn and the airtightness of the piston chamber 331 (pressurizing chamber 331b) can no longer be maintained.

[0049] The inventors of the present application have noticed that if Bellofram 38 is damaged and the piston chamber 331 (pressurizing chamber 331b) cannot be kept airtight, the piston 34 does not operate sufficiently and the actual opening becomes smaller than the target opening (the opening specified by the opening command value). As a result, it has been confirmed through experiments that it is possible to determine whether Bellofram 38 is damaged by calculating the opening difference, which is the difference between the opening command value and the actual opening, and monitoring the opening difference. More specifically, it is possible to determine that Bellofram 38 is damaged when the opening difference is equal to or greater than a predetermined threshold value. Therefore, according to the vacuum pressure control system 1 described in (1), the control device 70 is characterized by being equipped with an abnormality detection program 702a that calculates an opening difference, which is the difference between the opening command value output to the vacuum on-off valve 30 and the actual opening, which is the actual opening of the valve body 40 driven by the opening command value, and determines that the bellofram 38 is damaged when the opening difference is equal to or greater than a first predetermined threshold value, thereby making it possible to detect damage to the bellofram 38 used in the vacuum on-off valve 30.

[0050] (2) In the vacuum pressure control system 1 described in (1), the first predetermined threshold is preferably set to a value between 0.5% and 2.0%.

[0051] The inventors of the present application confirmed through experiments that it is possible to more reliably detect damage to bellofram by setting the first predetermined threshold value between 0.5% and 2.0% inclusive. This is because if the first predetermined threshold value is set to a value smaller than 0.5%, there will be many false positives, and if the first predetermined threshold value is set to a value larger than 2.0%, damage to bellofram cannot be detected quickly.

[0052] (3) In the vacuum pressure control system 1 described in (1) or (2), it is preferable that the abnormality detection program 702a calculates the opening difference at one-second intervals and determines that the bellofram 38 is damaged when the opening difference is equal to or greater than a first predetermined threshold value three or more times in succession.

[0053] In the vacuum on-off valve 30, the difference between the opening command value and the actual opening may suddenly become large due to the occurrence of hunting, in which the opening of the valve body 40 changes oscillatingly. For this reason, if it were to be determined that the bellofram 38 is damaged every time the opening difference is equal to or greater than the first predetermined threshold, there is a risk of erroneously detecting that the bellofram 38 is damaged even when the bellofram 38 is not damaged. According to the vacuum pressure control system 1 described in (3), the opening command and the actual opening are compared at one-second intervals, and when the difference is equal to or greater than the first predetermined threshold three or more times in succession, it is determined that the bellofram 38 is damaged, thereby preventing erroneous detection. The reason for the phrase "three or more times in succession" is that there is a risk of erroneous detection due to hunting if it is compared two times in succession.

[0054] (4) In the vacuum pressure control system 1 described in any one of (1) to (3), it is preferable that the abnormality detection program 702a calculates the opening difference when the pressure value of the vacuum chamber 11 exceeds a second predetermined threshold value.

[0055] (5) In the vacuum pressure control system 1 described in (4), the second predetermined threshold value is preferably a target value plus a value that is 0.2% to 1% of the target value.

[0056] In the vacuum on-off valve 30, the difference between the opening command value and the actual opening may suddenly become large due to the occurrence of hunting, in which the opening of the valve body 40 changes in an oscillatory manner. For this reason, if it is determined that the bellofram 38 is damaged in all cases where the opening difference is equal to or greater than the first predetermined threshold, there is a risk of erroneously detecting that the bellofram 38 is damaged even when the bellofram 38 is not actually damaged. In view of this, the inventors of the present application have focused on the fact that when the bellofram 38 is damaged and the actual opening becomes smaller than the target opening (the opening specified by the opening command value), the vacuum chamber 11 is not sufficiently evacuated, so that the pressure value of the vacuum chamber 11 increases over time, and have confirmed through experiments that it is possible to prevent erroneous detection by starting calculation of the opening difference when the pressure value of the vacuum chamber 11 exceeds a second predetermined threshold. The second predetermined threshold is, for example, a value obtained by adding a value of 0.2% to 1% of the target value to the target value. The reason for specifying "0.2% or more and 1% or less" is that if the threshold value is set to a value that is less than 0.2% of the target value plus the target value, it is not possible to reliably prevent false positives, and if the threshold value is set to a value that is more than 1% of the target value plus the target value, damage to the bellofram cannot be detected quickly.

[0057] The above embodiment is merely an example and does not limit the present invention in any way. Therefore, the present invention can be improved and modified in various ways without departing from the scope of the present invention. For example, in this embodiment, the Bellofram 38 is described as being formed by integrally molding a base fabric with a fluororubber (e.g., FKM, etc.), but it may be formed of rubber alone without using a base fabric. [Explanation of symbols]

[0058] 1 Vacuum pressure control system 11 Vacuum chamber 15 Vacuum Pump 30 Vacuum shutoff valve 31 Drive unit 33 Piston chamber 34 Piston 38 Belloflam 39 Drive shaft 40 Valve body 70 Control device 702a Anomaly Detection Program

Claims

1. a vacuum on-off valve disposed between a vacuum chamber and a vacuum pump for evacuating the vacuum chamber, the vacuum on-off valve controlling a pressure value of the vacuum chamber by adjusting an opening degree of a valve body; a control device that outputs an opening command value to the vacuum on-off valve for instructing the opening required to adjust the pressure value to a target value; A vacuum pressure control system comprising: the vacuum on-off valve includes a drive unit that applies a drive force to the valve body based on the opening command value; the drive unit includes a drive shaft connected to the valve body, a piston connected to the drive shaft on the opposite side to the valve body, a cylinder including a piston chamber for accommodating the piston, and a bellofram held by the piston to define the piston chamber; The control device includes: Calculating an opening difference, which is a difference between the opening command value output to the vacuum on-off valve and an actual opening, which is an actual opening of the valve body driven by the opening command value; an abnormality detection program for determining that the bellofram is damaged when the opening difference is equal to or greater than a first predetermined threshold; A vacuum pressure control system characterized by:

2. 2. The vacuum pressure control system according to claim 1, The first predetermined threshold is set between 0.5% and 2.0%. A vacuum pressure control system characterized by:

3. 3. The vacuum pressure control system according to claim 1, The abnormality detection program includes: The calculation is performed at 1 second intervals; determining that the bellofram is damaged when the opening difference is equal to or greater than the first predetermined threshold value three or more times in succession; A vacuum pressure control system characterized by:

4. 3. The vacuum pressure control system according to claim 1, the abnormality detection program performs the calculation when a pressure value of the vacuum chamber exceeds a second predetermined threshold value; A vacuum pressure control system characterized by:

5. 5. The vacuum pressure control system according to claim 4, the second predetermined threshold value being the target value plus a value not less than 0.2% and not more than 1% of the target value; A vacuum pressure control system characterized by:

6. 4. The vacuum pressure control system according to claim 3, the abnormality detection program performs the calculation when a pressure value of the vacuum chamber exceeds a second predetermined threshold value; A vacuum pressure control system characterized by:

7. 7. The vacuum pressure control system according to claim 6, the second predetermined threshold value being the target value plus a value not less than 0.2% and not more than 1% of the target value; A vacuum pressure control system characterized by:

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