Patent ID: 12209679

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments.

FIG.1illustrates a fluid supply system100incorporating a fluid control device10according to an embodiment of the present invention. The fluid supply system100has a gas supply source2; an upstream on-off valve V1provided downstream of the gas supply source2; a tank4connected downstream of the upstream on-off valve V1, and a fluid control device10provided downstream of the tank4.

A process chamber6in which a gas G is used is connected to a downstream side of the fluid control device10. A vacuum pump8is connected to the process chamber6. The vacuum pump8is used for evacuating the inside of the process chamber6and the flow path.

The fluid supply system100controls the flow rate of the gas G supplied from the gas supply source2and stored in the tank4using the fluid control device10, and supplies the gas G to the process chamber6. For this object, the fluid control device10includes a valve device V2of which opening degree can be finely adjusted, a pressure sensor PT provided upstream of the valve device V2, and a temperature sensor T provided in the valve device V2. The fluid control device10is configured to control the opening degree of the valve device V2in accordance with an output of the pressure sensor PT (and the temperature sensor T).

As the upstream on-off valve V1, a fluid driven valve such as AOV (Air Operated Valve) or a valve (on-off valve) having excellent responsivity and shut-off property is preferably used, such as a solenoid valve or an electrically operated valve. On the other hand, as the valve device V2with an adjustable opening degree, a valve of which opening degree can be finely adjusted by using a piezo actuator or the like is preferably used. However, in the present embodiment, as will be described later, a valve device V2having an integrated structure combining a piezoelectric actuator and a fluid driven valve is used.

In addition, the valve device V2may be configured by using a plurality of valves instead of using a single valve, for example, the valve device V2may be configured by a piezoelectric valve and a fluid driven valve being arranged in series or in parallel. Hereinafter, in the present specification, “the valve device V2is closed” means that at least one valve is closed and the flow path of the fluid control device10is closed, and “the valve device is open” means that at least one valve is open and the flow path of the fluid control device10is open.

In the fluid supply system100, first, the upstream on-off valve V1is opened while the valve device V2of the fluid control device10is closed, and the gas is filled into the tank4from the gas supply source2. Thereafter, the flow path including the tank4is closed by closing the upstream on-off valve V1. And then, by opening the valve device V2of the fluid control device10, the gas in the tank4is supplied to the process chamber6. At this time, by adjusting the opening degree of the valve device V2of the fluid control device10, it is possible to control the flow rate of the gas flowing out of the tank4.

Further, after supplying only a desired amount of the gas in the tank4to the process chamber6, and then stop supplying by closing the valve device V2of the fluid controlling device10. Thereby, one process is completed. Then, by opening the upstream on-off valve V1, the tank4is refilled with gas, and a subsequent process can be performed in the same manner as described above. In this manner, the fluid supply system100can repeatedly supplying the gas, which was supplied to the tank4, to the process chamber6.

FIG.2illustrates a more detailed configuration of the fluid control device10, andFIG.3illustrates a detailed configuration of the valve device V2included in the fluid control device10.

As illustrated inFIG.2, the fluid control device10includes a pressure sensor PT, a temperature sensor T, a valve device V2having an adjustable opening degree, and a control circuit12for controlling an operation of the valve device V2based on an output of the pressure sensor PT.

In the present embodiment, the valve device V2includes a main actuator22for opening/closing a valve mechanism20by using compressed air as a driving fluid, and a sub actuator24for electrically opening/closing the valve mechanism20by using piezoelectric elements. The valve device V2can be largely opened/closed by supplying a compressed air14, and the opening degree can be adjusted more precisely by controlling the applied voltage to the piezoelectric element (piezoelectric drive signal Spz). Such a valve is disclosed in Patent Literature 2 and JPA 2021-32391 by the present applicant. For reference, the entire disclosure of JPA 2021-32391 is incorporated herein by reference.

Further, the valve device V2is provided with an opening/closing detection device26for detecting opening/closing of the valve element. As the opening/closing detection device26, a limit switch is mainly used. The limit switch is constituted by an electric contact arranged to be able to abut on an upper end of the operating member which is moved by the main actuator22, and can generate a signal (opening/closing detection signal Ssw) indicating the actual opening/closing of the valve based on an energization of the contact point. A fluid-driven valve with a limit switch is disclosed, in Patent Literature 3 (WO2018/021327), for example.

The control circuit12may receive the pressure signal Spr indicating the fluid pressure measured by the pressure sensor PT and the temperature signal Stm indicating the temperature measured by the temperature sensor T via an AD converter15, and may receive the opening/closing detection signal Ssw from the opening/closing detection device26via an input circuit16. In addition, the control circuit12can apply a driving voltage to the sub actuator (piezoelectric actuator) of the valve device V2by using a booster circuit17. The booster circuit17is used to convert a control signal from the control circuit12into a driving voltage to be applied to the piezoelectric element.

The opening/closing detection device26may be any device as long as the opening/closing of the valve element can be detected, and may be a device that detects the opening/closing state from a change in the piezoelectric voltage other than the limit switch, or a device that detects the opening/closing state by measuring the height of a pistons22aor the like using a laser, a proximity sensor, etc.

In the present embodiment, the control circuit12, the AD converters15, the inputting circuit16, and the boosting circuit17are provided on a circuit board11built in the fluid control device10. However, the present invention is not limited thereto, and at least one of them may be provided outside the fluid control device10. The control circuit12is typically a digital signal processing circuit including a CPU, a memory, and the like, and includes a computer program for executing an operation to be described later. The control circuit12can be realized by a combination of hardware and software.

FIG.3illustrates a more specific exemplary configuration of the valve device V2(however, the opening/closing detection device26is omitted). As illustrated, the valve device V2includes an operation member28for opening/closing a diaphragm valve element20a, a main actuator22for largely moving the operating member28, and a sub actuator24for smally moving the operating member28.

In the present embodiment, the valve device V2is a normally closed valve, and when the main actuator22and the sub actuator24are not driven, the diaphragm valve element20ais pressed against a valve seat (not shown) by a biasing force received from a main elastic member (here, a coiled spring) or the like via the operating member28and a valve element pusher28afixed to a distal end thereof. The valve seat is usually provided as an annular protruding surface provided adjacent to the center of the diaphragm valve element20a.

As the main actuator22, an air-driven actuator that moves the operating member28up and down using compressed air as a driving fluid is used. The main actuator22includes a plurality of annular pistons22a, and is able to move the operating member28up and down by suppling compressed air through a supply pipe22b.

In addition, a pressure regulator (e.g., an electropneumatic regulator) for supplying compressed air of an arbitrary pressure to the pistons22amay be connected to the supply pipe22b. By using the pressure regulator, the valve opening degree can be adjusted stepwise by adjusting the operating pressure of the main actuator22to an arbitrary magnitude. However, the main actuator22may be configured to perform only the opening/closing operation of the valve device V2by controlling the supply/stop of the high-pressure air using a solenoid valve or the like, without providing the pressure regulator.

As the sub actuator24, a piezo actuator may be used. The sub actuator24is slidably disposed inside of the operating member28with respect to the operating member28. In the sub actuator24, the degree of elongation thereof is controlled by controlling the voltage to be applied to the piezoelectric element.

Furthermore, the valve device V2includes a lower elastic member30(here, a coiled spring) abutting on a flange portion28bof the operating member28, and an upper elastic member (here, a Belleville spring)32positioned above the sub actuator24. The upper end of the lower elastic member30and the upper elastic member32are restricted respectively by a body34and a cap36that are stationary portions and the lower elastic member30can bias the operation member28downward, and the upper elastic member32can bias the sub actuator24downward.

In the valve device V2having the above described configuration, when the main actuator22and the sub actuator24are not driven, the diaphragm valve element20ais pressed against the valve seat by the biasing force of the lower elastic member30that presses the flange portion28bof the operating member28downward and the biasing force of the upper elastic member32that presses the sub actuator24downward.

On the other hand, to open the valve, compressed air is supplied to the main actuator22, against the biasing force of the lower elastic member30and the upper elastic member32, the main actuator22lifts the operating member28upward by the pistons22a. At this time, since the load is balanced, the movement of the operation member28is relatively smoothly performed, and it is easy to adjust the opening degree corresponding to the operation pressure. Furthermore, the valve opening degree can be adjusted more precisely by controlling the voltage to be applied to the sub actuator24while opening the valve using the main actuator22.

In this manner, by using the valve device V2capable of performing the opening/closing operation by the main actuator22and the fine adjustment of the opening degree by the sub actuator24, it is possible to not only flow a gas having a large flow rate with high responsivity, but also accurately control the flow rate of the gas by precisely adjusting the opening degree.

In addition, it is possible to use only one actuator and one valve as the valve device V2, as long as both the opening/closing operation and the opening degree fine adjustment can be realized by only any one of the main actuator and the sub actuator.

Furthermore, the main actuator and the sub actuator are not necessarily provided in one valve, but may be provided in separate valves. In this case, each valve may be provided in the same flow path, or may be provided in a branch flow path by branching the flow path.

FIG.4illustrates a fluid control device10A in which each of the branch flow paths is provided with a valve. In the fluid control device10A, the valve device V2is configured by a valve V2a(sometimes referred to as a main valve) including the main actuator22and a corresponding valve element, and a valve V2b(sometimes referred to as a sub valve) including the sub actuator24and a corresponding valve element. The main valve V2aand the sub valve V2bconstituting the valve device V2are respectively installed in the branched flow paths downstream of the pressure sensor PT, and it is possible to not only speedily open/close the flow path using the main valve V2a, but also finely adjust the flow rate of the gas flowing downstream of the fluid control device10A by using the sub valve V2b.

In the fluid control device10A, a temperature sensor T is provided to measure the body temperature of the main valve V2a, but is not limited thereto. The temperature sensor T may be provided in each of the main valve V2aand the sub valve V2b, or may be provided in a common flow path in the vicinity of the pressure sensor PT. The temperature sensor may be provided in any manner as long as the temperature of the valve device V2or the gas temperature can be appropriately measured.

Referring again toFIG.1, the operation of the fluid control device10will be described. The fluid control device10is configured to measure a pressure drop using the pressure sensor PT when opening the valve device V2to allow the gas in the tank to flow out after closing the upstream on-off valve V1. Then, when the measured pressure drop is different from the reference pressure drop curve given in advance, the operation of the sub actuator24is controlled so that the pressure matches the reference pressure drop curve.

This allows the supply of the gas in the tank to follow the reference pressure drop curve in each process. Therefore, it is possible to perform a stable gas supply in which variation in each process is reduced.

As the reference pressure drop curve, typically, a pressure drop curve measured using the pressure sensor PT in a process executed at first, sometimes referred to as a first process, is used. By determining the reference pressure drop curve in this manner, it is possible to perform gas supply in the second and subsequent processes with a gas flow as same as that of the first process. Thus, even in the gas supply mode in which the primary side pressure fluctuates, it is possible to perform the gas supply with the same pressure fluctuation and to realize a stable gas supply each time.

However, the reference pressure drop curve does not necessarily have to be obtained in the first process, and may be obtained in an intermediate process and reflected in a subsequent process. Further, the reference pressure drop curve is not limited to the one obtained by measurement in a process, and may be one obtained in advance by measurement under an ideal environment, or may be one set as an ideal curve regardless of measurement.

Hereinafter, the reason for controlling the flow rate at the time of gas supply using the reference pressure drop curve will be described.FIG.5illustrates a pressure drop curve after opening the valve device V2in a comparative example, in particular, illustrates respective pressure drop curves P90-P110 when the initial tank pressure differs at 90-110 kPa abs. In this case, the graph when the initial pressure is 100 kPa abs (P100) is set as the reference pressure drop curve. In addition,FIG.5also illustrates the driving voltage Pz90-Pz110 of the piezoelectric element, and in this comparative example, the driving voltage of the piezoelectric element is fixed to be constant at 50% regardless of the initial pressure.

Note that the graph P90, P95, P100, P105 and P110 indicates a pressure drop curve at an initial pressure 90 kPa, 95 kPa, 100 kPa, 105 kPa and 110 kPa, respectively, and the graph Pz90, Pz95, Pz100, Pz105, Pz110 indicates a piezo drive voltage at an initial pressure 90 kPa, 95 kPa, 100 kPa, 105 kPa and 110 kPa respectively.

As can be seen fromFIG.5, after opening the valve device V2using the main actuator, the gases flow out over time and the pressure drops, regardless of the initial pressure in the tank. At this time, the pressure downstream of the valve device V2is maintained at a vacuum pressure (100 torr or less) by using a vacuum pump, for example.

However, it can be seen that the pressure drop curve P90-P110 is slightly different due to the difference in the initial pressure, resulting in a difference in the flow of the gas being supplied. When a difference occurs in the flow of the gas in this way, the flow rate of the gas supplied to the process chamber and the entire supply amount of the gas supplied in a certain period of time become different for each initial pressure. As a result, a stable process may not be continuously performed.

In order to suppress the change in the gas flow due to the initial pressure, it is conceivable to control the gas pressure in the tank so that the initial pressure becomes constant based on the measurement by the pressure sensor when the gas is stored in the tank. Initial pressure can be controlled by adjusting the timing of closing the upstream on-off valve V1.

However, in reality, it may be difficult to keep the gas pressure in the tank constant for each process depending on the environment at the time of gas storage. Further, even if the initial pressure can be made constant, the pressure drop curve when the valve device V2is opened differs depending on the machine difference of the valve device V2, the volume of the tank, the fluid, or the temperature of the environment, and the like. It is also conceivable that the flow rate characteristics of the valve device V2change over time. Therefore, in order to perform stable gas supply, it is preferable to set the reference pressure drop curve in advance and adjust the opening degree of the valve device V2based on the reference pressure drop curve for each process.

Patent Literature 4 discloses a technique for detecting an abnormality in a restriction part using a pressure drop characteristic upstream of the restriction part in a pressure-type flow rate control device. In addition, Patent Literature 5 discloses that, at the time of the flow rate falling, the drive control of the piezo valve is performed with reference to a reference pressure drop characteristic. However, neither of the patent documents discloses nor suggests the flow control performed with reference to the reference pressure drop characteristic when supplying the fluid through a valve, accompanied by the primary side pressure drop, while the upstream on-off valve is closed, as in the fluid control device of the present embodiment.

Hereinafter, a specific control procedure of the valve device V2will be described.FIG.6andFIG.7are exemplary flow charts illustrating adjustments of the opening degree of the valve device V2in accordance with a reference pressure drop curve.FIG.6illustrates a flow for obtaining an approximate polynomial corresponding to the reference pressure drop curve by polynomial regression, andFIG.7illustrates a flow for controlling the operation of the valve device V2based on the obtained approximate polynomial (reference equation) and the measured pressure.

First, as shown in step S1ofFIG.6, in order to obtain a reference pressure drop curve, a valve operating pressure is supplied to the main actuator of the valve device V2from a state where the gas is stored and sealed in the tank, thereby opening the valve device V2and generating a reference flow. As a result, the gas stored in the tank in the sealed state (the upstream on-off valve V1is closed) rapidly flows out to the downstream side through the valve device V2, and the pressure in the tank also decreases. At this time, as shown in steps S2-S3, the pressure upstream of the valve (corresponding to the tank pressure) is sampled by using the pressure sensor. Sampling is continued, for example, until the output of the pressure sensor reaches a preset lower limit set value, or until a predetermined time has elapsed.

Note that the time at which the valve device V2is opened in step S1can be accurately specified by using the opening/closing detection device26. This makes it possible to more accurately measure the pressure drop from the time when the valve is actually opened to the time when the predetermined period has elapsed.

After the pressure drop data has been obtained by sampling, as shown in step S4, an approximate polynomial is derived from the obtained data by software processing (polynomial regression). The order of the polynomial may be appropriately set, for example, it may be set to a sextic equation. Here, the approximate equation is expressed in a form such as y=a1x6+a2x5+a3x4+a4x3+a5x2+a6x+a7, where y is a pressure correspondence, x is a time, and a1-a7are coefficients corresponding to the approximate curve, and are coefficients determined based on the pressure drop data.

FIG.8illustrates a pressure drop data (sampled data) Dp obtained by measurement, and a function graph Cp corresponding to the approximate polynomial obtained from the pressure drop data. In this case, it can be seen that the sampling period is set to 100 ms, and a sufficiently approximate curve can be obtained by using the sextic polynomial.

After the approximate polynomial corresponding to the reference pressure drop curve is obtained in this manner, a valve control operation is performed in a subsequent process to match the reference pressure drop curve.

In the subsequent process, as shown in step S5ofFIG.7, the valve device V2is opened to allow the gas in the tank to flow out from the state where the gas is stored and sealed in the tank. At this time, the pressure upstream of the valve is measured using the pressure sensor PT, and similarly, the temperature of the gas is measured using the temperature sensor T.

Next, as shown in step S6, the control command value y (target pressure value based on the reference pressure drop curve) for the present time x is obtained by calculation using the previously determined approximate polynomial. In addition, as shown in step S7, the present actual pressure measured using the pressure sensor can be obtained. The calculation of the control command value y (step S6) and the acquisition of the present pressure value (step S7) may be performed vice versa or may be performed simultaneously.

Further, in step S7, the temperature at the present pressure may be corrected based on the temperature measured by using the temperature sensor T. This is for reducing the temperature dependency of the output of the pressure sensor PT, and the measured pressure may be corrected according to the temperature based on the temperature dependence information (temperature-pressure coefficient table, etc.) stored in advance in the memory of the control circuitry12, for example. In this way, a more accurate pressure value can be obtained regardless of the temperature, and the flow rate can be controlled more appropriately.

Next, as shown in step S8, feedback control based on the current pressure value is performed, specifically, the current pressure value is compared with the control command value y, and the piezoelectric actuator is PID controlled. As a result, the opening/closing operation of the valve is performed so as to approach the control command value y.

Here, the reference driving voltage of the sub actuator (piezoelectric actuator)24of the valve device V2is set to 50% of the rated voltage (voltage corresponding to the set maximum opening degree). In this case, in step S8, when the present pressure value is lower than the control command value y, the piezo drive voltage can be increased more than the reference value, and the valve opening degree can be slightly decreased, so that the pressure value can be brought close to the control command value y. In addition, when the current pressure value exceeds the control command value y, the piezoelectric drive voltage can be decreased from the reference value, and the valve opening degree can be slightly increased, so that the pressure value can be brought close to the control command value y.

The PID control of the piezo actuator based on the reference pressure drop curve (here polynomial) is continued until the ending time is confirmed in step S9. At the ending time, the current pressure value may be less than the predetermined value, or the predetermined time may have elapsed.

FIG.9is a graph illustrating pressure drop curves (solid line) P90-P110 and piezo drive voltages (dashed line) Pz90-Pz110 resulting from the valve operation control described above. When the reference initial pressure is 100 kPa (P100), the initial pressure may be higher (P105, P110) than it, or may be lower (P90, P95) than it.

As can be seen fromFIG.9, when the initial pressure (90 kPa, 95 kPa) is less than the reference value (100 kPa), the valve opening degree is slightly reduced by increasing the piezo drive voltage (Pz90, Pz95) by more than 50%, thereby increasing the pressure and controlling the valve opening degree so as to approach the reference pressure drop curve. As time progresses, the pressure drop curve approaches the reference pressure drop curve, while the piezo drive voltage (Pz90, Pz95) moves back to 50% of the reference value.

When the initial pressure (105 kPa, 110 kPa) is larger than the reference value, the valve opening degree is slightly increased by decreasing the piezo drive voltage (Pz105, Pz110) by more than 50%, thereby decreasing the pressure, and the valve opening degree is controlled so as to approach the reference pressure drop curve. As time progresses, the pressure drop curve approaches the reference pressure drop curve, while the piezo drive voltage moves back to 50% of the reference value.

In the valve device V2according to the present embodiment, driving fluid is not supplied to the main actuator when the valve device is closed, and the driving voltage of the sub actuator is set to 0. Therefore, even when the initial pressure is the reference value (100 kPa), it is possible to confirm an operation in which the driving voltage Pz100 of the piezo actuator is increased to 50% of the reference value due to the PID control after the valve is released.

Next, another embodiment for more quickly shifting to the reference pressure will be described. In the present embodiment, the control command value y is corrected based on the outputs of the pressure sensor PT and the temperature sensor T, and the driving voltage of the sub actuator (piezo actuator) of the valve device V2is controlled based on the corrected control command value y′.

As illustrated inFIG.10, in the present embodiment, a deviation between the control command value y and the present pressure value FB is obtained in real time, and the corrected control command value y′ is generated by adding this deviation to the control command value y. In the illustrated embodiment, since the actual pressure value FB is smaller than the control command value y, a corrected control command value y′ exceeding the control command value y is generated. This state corresponds to, for example, a state in which the initial pressure is smaller than the reference initial pressure, and therefore the valve opening degree needs to be made smaller in order to match the reference pressure drop curve.

According to the control command value y′ (sometimes referred to as the corrected command value y′) corrected in this way, in the PID control, the driving voltage of the piezoelectric actuator is greatly reduced, and the operation of reducing the valve opening degree is performed more quickly. This makes it possible to adjust the pressure faster to match the reference pressure drop curve.

FIG.11illustrates an exemplary flow chart for adjusting the opening degree of the valve device V2in accordance with the reference pressure drop curve in the present embodiment.

First, same as the flow chart shown inFIG.7, the valve device V2is opened in step S10from the state where the gas is stored in the tank, the control command value y is calculated by using the polynomial (approximate expression of the reference pressure drop curve) in step S11, and the present actual pressure value measured by using the pressure sensor is obtained in step S12.

Next, in the present embodiment, an operation of correcting the control command y is performed as shown in step S13. This operation is performed by obtaining a deviation (FB-y) between the current pressure value FB obtained in step S12and the control command value y obtained in step S11, and subtracting this deviation from the control command value y.

Here, when the current pressure value FB is smaller than the control command value y, the deviation (FB-y) takes a negative value, so that the corrected control command value y′ is larger than the control command value y by only the deviation. On the other hand, when the present pressure value FB is larger than the control command value y, the deviation (FB-y) takes a positive value, so that the corrected control command value y′ is smaller than the control command value y by only the deviation.

Thereafter, as shown in step S14, the PID control of the piezo actuator is performed based on the corrected command value y′ (and the current pressure value FB). As a result, it is possible to adjust to the control command value y more quickly than that in the case of using the control command value y before correction. This operation is continued until the ending time is confirmed in step S15.

FIG.12is a graph illustrating a pressure drop (solid line) and piezo drive voltages (dashed line) as a result of performing valve operation control according to another embodiment of the present invention. The reference initial pressure is set as 100 kPa, the graph indicates the cases where the initial pressures are larger than it and the cases where the initial pressure are smaller than it.

As shown inFIG.12, in the present embodiment, it can be seen that the operation of quickly adjusting to the reference pressure drop curve is realized as compared with the case of the embodiment shown inFIG.9.

While embodiments of the present invention have been described above, various modifications are possible. For example, although an embodiment of using a piezo actuator as the sub actuator has been described above, the present invention is not limited thereto, and an actuator including a deformable material by electrical driving such as an electrically driven polymer material or an electroactive polymer material may be used. Note that the electrical driving includes applying a voltage to the element, supplying a current to the element, or forming an electric field around the element. Instead of the piezo actuator, an actuator including a solenoid utilizing a magnetic force may also be used.

Although a normally closed valve device has been described above, the valve device may be a normally open valve device. In addition, by adopting a structure in which an extension (an isolation member, not shown) can be inserted between the lower end portion of the piezoelectric element and the diaphragm pusher, the piezoelectric element can be prevented from being affected by temperature (high temperature or low temperature).

Although the aspect of using the valve device V2combining a fluid drive valve and a piezo actuator has been described above, the fluid control device may be configured by using a common valve having an adjustable opening degree such as a piezo valve.

INDUSTRIAL APPLICABILITY

The fluid control device, the fluid supply system, and the fluid supply method according to the embodiments of the present invention are preferably used in semiconductor manufacturing, for example.

REFERENCE SIGNS LIST

2Gas supply source4Tank6Process chamber8Vacuum pump10Fluid control device12Control circuit20Valve mechanism22Main actuator24Sub actuator26Opening/closing detection device100Fluid supply systemPT Pressure sensorT Temperature sensorV1Upstream on-off valveV2Valve device