JP7534147B2 - Flow rate control device, fluid control device, flow rate control method, and program for flow rate control device - Google Patents

Description

The present invention relates to a flow control device that controls, for example, the flow rate of a fluid.

In semiconductor manufacturing processes, various gases are supplied into a chamber while controlling the flow rate to a desired level. In recent years, there has been a demand in this field for faster flow rate control and improved flow rate accuracy (see Patent Document 1), and to meet this demand, a flow rate control device using two control valves has been proposed.

Specifically, this flow control device has a first valve, a pressure-type flow sensor, and a second valve provided in this order from the upstream side to the flow path. For example, the first valve is controlled so that the first pressure of a first pressure sensor provided upstream of a laminar flow element that constitutes the flow sensor is fed back to the first valve, and the first pressure is kept constant at a desired set pressure. In addition, the second valve is controlled so that the measured flow rate measured by the flow sensor is fed back to the second valve, and the measured flow rate is equal to the set flow rate. The set pressure is always set to a constant value regardless of the magnitude of the set flow rate.

Incidentally, pressure-type flow sensors are more sensitive at lower pressures, so the precision of flow control by the second valve can be improved by setting the set pressure to as low a value as possible and keeping the first pressure, which is the pressure upstream of the laminar flow element, at a low pressure.

However, if the set pressure is too low, the first pressure will not be able to sufficiently exceed the pressure loss in the laminar flow element and the second valve, and the pressure downstream of the second valve, making it impossible to flow a large flow rate of fluid downstream of the second valve. On the other hand, if the set pressure is set to a relatively high value in consideration of the range of the set flow rate, the sensitivity and measurement accuracy of the pressure-type flow sensor will deteriorate compared to its original capabilities when the set flow rate is small. Specifically, as shown in the graph of Figure 6, the higher the set pressure value and the higher the value of the second pressure P2, which is the pressure downstream of the fluid resistance, the lower the sensitivity of the differential pressure ΔP = _P1 - _P2 to the flow rate and the lower the measurement accuracy.

JP 2015-109022 A

The present invention was made in consideration of the above-mentioned problems, and aims to provide a flow control device that can maintain high sensitivity and measurement accuracy of the flow sensor even at low flow rates, while also being able to handle large flow rates.

That is, the flow control device according to the present invention is characterized by comprising a first valve provided in a flow path, a second valve provided in the flow path downstream of the first valve, a flow sensor that measures the flow rate of the fluid in the flow path between the first valve and the second valve, a flow controller that controls an operation amount input to the second valve so that the deviation between the measured flow rate measured by the flow sensor and a set flow rate is small, and a first valve controller that controls the first valve so that the deviation between the controlled amount and a target amount is small, using the operation amount input to the second valve by the flow controller or the opening degree of the second valve as a control amount.

The flow control method according to the present invention is a flow control method used in a flow control device including a first valve provided in a flow path, a second valve provided in the flow path downstream of the first valve, and a flow sensor that measures the flow rate of the fluid in the flow path between the first valve and the second valve, and is characterized by comprising a flow control step of controlling an operation amount input to the second valve so that the deviation between the measured flow rate measured by the flow sensor and a set flow rate is small, and a first valve control step of controlling the first valve in the flow control step so that the operation amount input to the second valve or the opening of the second valve is set as a control amount and the deviation between the control amount and a target amount is small.

In this case, for example, if the set flow rate changes from the initial flow rate value to a maintained flow rate value that is smaller than the initial flow rate value, the flow controller will change the operation amount input to the second valve so as to reduce the opening of the second valve, thereby attempting to reduce the flow rate of fluid that can pass through the second valve.

When the opening of the second valve changes, the deviation between the controlled amount and the target amount in the first valve controller increases, so the first valve controller changes the opening of the first valve to return the opening of the second valve to its original value. In this example, the flow rate of the fluid flowing into the flow sensor between the first and second valves is reduced, resulting in a state in which the measured flow rate is smaller than the set flow rate. The flow controller then increases the opening of the second valve to increase the flow rate of the fluid passing through the second valve and reduce the deviation.

By repeating the operation of the flow controller and the first valve controller for each control cycle, the opening of the second valve can be returned to the same opening that was maintained at the initial flow value even at the maintained flow value after the change.

Therefore, when a fluid is flowed at a small flow rate such as the maintenance flow rate value, the opening of the first valve is finally reduced to reduce the inflow of fluid, and the opening of the second valve can be increased so as not to provide resistance. As a result, the absolute pressure at the flow sensor is reduced, and the sensitivity and measurement accuracy of the flow sensor can be kept high. On the other hand, when a fluid is flowed at a large flow rate such as the initial flow rate value, the opening of the first valve is changed to be larger so that the opening of the second valve is maintained at a predetermined opening, and the inflow of fluid increases. Therefore, a large flow rate can be flowed by exceeding the pressure loss of the flow sensor and the second valve and the pressure downstream of the second valve. In this way, with the present invention, it is possible to maintain the sensitivity and measurement accuracy of the flow sensor high at a small flow rate, while also achieving the differential pressure required to flow a large flow rate.

When the flow sensor includes a fluid resistor provided between the first valve and the second valve, a first pressure sensor provided between the first valve and the fluid resistor, a second pressure sensor provided between the fluid resistor and the second valve, and a flow calculation unit that calculates the flow rate of the fluid flowing through the fluid resistor based on the first pressure measured by the first pressure sensor and the second pressure measured by the second pressure sensor, in order to fully utilize the sensitivity and measurement accuracy of the flow sensor, the target amount set in the first valve controller may be a constant value that maintains the opening of the second valve at a predetermined opening on the fully open side. In this way, the opening of the second valve is maintained at a large value, making it possible to reduce the pressure of the flow sensor located upstream of the second valve, thereby improving the sensitivity and measurement accuracy.

A specific control rule of the first valve controller is that when the opening of the second valve is smaller than the opening corresponding to the target amount, the first valve controller controls the opening of the first valve in a direction to reduce the opening. When the opening of the second valve becomes smaller than the target state, the opening of the first valve is reduced, and the flow rate supplied to the second valve is reduced. Therefore, the flow rate controller operates to increase the opening of the first valve in order to maintain the flow rate, so that the opening of the first valve can be maintained at the target opening.

A specific example of the configuration of the first valve and the first valve controller is one in which the first valve is a normally open type piezo valve, and the first valve controller controls the voltage applied to the first valve in a direction to increase when the control amount is smaller than the target amount.

Another example of the configuration of the first valve and the first valve controller is one in which the first valve is a normally closed type piezo valve, and the first valve controller controls the voltage applied to the first valve in a direction to decrease when the control amount is smaller than the target amount.

In order to achieve the same effect as the flow control device of the present invention by updating the program of an existing flow control device, it is sufficient to use a program for a flow control device that includes a first valve provided in a flow path, a second valve provided in the flow path downstream of the first valve, and a flow sensor that measures the flow rate of the fluid in the flow path between the first valve and the second valve, the program causing a computer to function as a flow controller that controls an operation amount input to the second valve so as to reduce the deviation between the measured flow rate measured by the flow sensor and a set flow rate, and a first valve controller that controls the first valve so as to reduce the deviation between the control amount and a target amount, using the operation amount input to the second valve by the flow controller or the opening of the second valve as a control amount.

The program for the flow control device may be distributed electronically or may be recorded on a program recording medium such as a CD, DVD, BD, or flash memory.

A fluid control device including a first valve provided in a flow path, a second valve provided in the flow path downstream of the first valve, a fluid sensor that measures a physical quantity of the fluid in the flow path between the first valve and the second valve, a fluid controller that controls an operation amount input to the second valve so that the deviation between the measurement amount measured by the fluid sensor and a set amount is small, and a first valve controller that controls the first valve so that the deviation between the operation amount input to the second valve by the fluid controller or the control amount, which is the opening of the second valve, and a target amount is small, can control the physical quantity of the fluid, such as the flow rate, pressure, or concentration, to match the set amount, while maintaining the opening of the second valve at a desired opening, thereby maintaining a pressure suitable for operating the fluid sensor. Therefore, it is possible to improve the control accuracy compared to the conventional method, regardless of the type of physical quantity to be controlled.

For example, in the case of a process in which gas is supplied into a chamber to form plasma, a minimum amount of plasma continues to be generated even during periods when the process is paused in the chamber. This is to keep impurities in the chamber suspended in the air and prevent them from accumulating on the substrate. For this reason, a specified flow rate of gas is supplied to the chamber during the process, and when the pause period begins, the gas flow rate is reduced to the minimum maintenance flow rate at which plasma is maintained.

In a flow control device that includes a flow sensor, a control valve provided downstream of the flow sensor, and a flow controller that controls the control valve based on the deviation between the measured flow rate of the flow sensor and the set flow rate, if a set flow rate is set for the flow controller such that the flow rate value drops significantly in a stepwise manner to achieve the above-mentioned flow rate control, and the opening of the control valve corresponding to the maintained flow rate is close to being fully closed, a situation may occur in which gas is not momentarily supplied to the chamber.

Specifically, since the flow sensor is located upstream of the control valve, a time lag occurs with respect to the flow rate of gas actually passing through the control valve. Therefore, the flow controller reduces the opening of the control valve to achieve the maintained flow rate, and even if the control valve is at an opening suitable for achieving the maintained flow rate at a certain point in time, the flow sensor will output a measured flow rate greater than the maintained flow rate. Then, the flow controller further reduces the opening of the control valve to eliminate the deviation between the measured flow rate and the set flow rate, which may cause the control valve to be fully closed. In other words, even if the output of the flow sensor is not zero as shown in the graph of FIG. 7, the opening of the control valve is zero, so in reality, no gas flows downstream of the control valve as shown in FIG. 8, and plasma cannot be maintained in the chamber.

To solve such problems, a flow control device can be used that includes a flow sensor that includes a sensing mechanism that is provided in a flow path and outputs an output signal corresponding to the flow rate of the fluid flowing through the flow path, a flow calculation unit that calculates the flow rate based on a measurement value indicated by the output signal of the sensing mechanism and a flow characteristic value corresponding to the measurement value, a control valve that is provided upstream or downstream of the flow sensor, a flow controller that controls the control valve so as to reduce the deviation between the measured flow rate measured by the flow sensor and the set flow rate, and a reference governor that sets the set flow rate, which is a command flow rate with a time delay corresponding to the measurement value indicated by the output signal of the sensing mechanism, in the flow controller.

In this way, the reference governor sets the set flow rate in the flow controller by applying a time delay according to the measurement indicated by the output signal of the sensing mechanism, so the time delay of the flow sensor can be reflected in the set flow rate. Therefore, since deviation between the measured flow rate and the set flow rate due to the time delay of the flow sensor is unlikely to occur, even when the flow controller is trying to achieve a flow rate equivalent to an opening close to full closure, it is possible to prevent the control valve from being controlled to full closure.

In addition, since the reference governor imparts a time delay to the set flow rate according to the measured value indicated by the output signal of the sensing mechanism, it is possible to accurately reflect, for example, differences in the magnitude of the time delay that appears in the flow sensor due to differences in the magnitude of the flow rate. Therefore, compared to a case where a constant time delay is directly applied to the set flow rate, deviations due to the time delay of the flow sensor are less likely to occur, and it is possible to prevent the control valve from closing completely and interrupting the supply of fluid at low flow rates.

A specific example of a configuration for allowing the reference governor to accurately reflect the time delay of the flow sensor in the set flow rate is one in which the sensing mechanism includes a fluid resistance, a first pressure sensor provided upstream of the fluid resistance, and a second pressure sensor provided downstream of the fluid resistance, the flow calculation unit includes a coefficient determination unit that determines the flow resistance, which is the flow characteristic value, based on the first pressure and the second pressure, which are measured values indicated by the output signals of the first pressure sensor and the second pressure sensor, and an output unit that calculates the flow rate based on the first pressure, the second pressure, and the flow resistance, and the reference governor is configured to calculate the set flow rate based on the flow resistance determined by the coefficient determination unit and the command flow rate, and set the set flow rate in the flow controller.

The device includes a first valve provided in a flow path, a second valve provided in the flow path downstream of the first valve, a fluid resistance provided in the flow path between the first valve and the second valve, a first pressure sensor that measures the pressure in a first volume that is a volume between the first valve and the fluid resistance in the flow path, a second pressure sensor that measures the pressure in a second volume that is a volume between the fluid resistance and the second valve in the flow path, and a flow rate calculation unit that calculates the flow rate of the fluid flowing through the fluid resistance based on the first pressure measured by the first pressure sensor and the second pressure measured by the second pressure sensor. In a flow control device, in order to accurately identify the size of the first volume and to further improve the accuracy of flow control by appropriately setting various parameters determined from the size of the first volume for each device even if there is a manufacturing error, etc., a diagnoser that diagnoses the volume of the first volume or the second volume may be provided, and the diagnoser may calculate the size of the first volume based on an integrated value of the flow rate calculated by the flow calculation unit over a predetermined period and the amount of change in the first pressure during the predetermined period when the first valve is open and the second valve is closed.

In order to accurately identify the size of the second volume, the diagnostic device may calculate the size of the second volume based on an integrated value of the flow rate calculated by the flow rate calculation unit over a predetermined period of time while the second valve is open and the first valve is closed, and on the amount of change in the second pressure during the predetermined period of time.

To ensure that the flow of fluid into or out of the volume whose size has been identified is stable and identification errors are less likely to occur, the specified period should be the period from when the absolute value of the difference between the first pressure and the second pressure becomes maximum until when the first pressure and the second pressure become equal.

In order to be able to verify the correctness of the identified sizes of the first volume and the second volume in another way, the diagnostic device may calculate a volume ratio between the first volume and the second volume based on the difference between the first pressure at the start of the specified period and the first pressure at the end of the specified period, and the difference between the second pressure at the start of the specified period and the second pressure at the end of the specified period.

In this way, with the flow control device according to the present invention, the second valve is controlled by flow feedback, and the first valve, which is located upstream of the second valve, is controlled so that the control amount related to the opening of the second valve matches the target amount, thereby realizing a low pressure that allows the sensitivity and measurement accuracy of the flow sensor to be demonstrated when a small flow rate is flowed, while at the same time, when a large flow rate is flowed, it is possible to realize a pressure difference that exceeds various pressure losses and downstream pressure.

1 is a schematic diagram showing a flow rate control device according to an embodiment of the present invention; 2 is a schematic diagram showing a configuration related to flow control by the flow control device and maintaining the opening degree of a second valve in the embodiment. FIG. 5 is a schematic graph showing the operation of a first valve and a second valve of the flow rate control device in the embodiment. 2 is a schematic diagram showing a configuration related to a reference governor of the flow control device in the embodiment. FIG. FIG. 13 is a schematic diagram showing an example of control of a first valve and a second valve in a conventional flow control device. 1 is a graph showing a relationship between flow rate and differential pressure, which indicates a change in sensitivity with respect to absolute pressure in a pressure-based flow sensor. 11 is a schematic diagram showing changes in the opening degree of a first valve and a second valve in a conventional flow control device. FIG. 11 is a schematic diagram showing an example of a flow rate change in a conventional flow rate control device. FIG. 13 is a schematic diagram showing a flow rate control device according to another embodiment of the present invention. FIG. 13 is a schematic diagram showing a deviation of the identified first volume or second volume. 11 is a flowchart showing an operation related to identification of a second volume that is performed when a process is stopped, etc. 11 is a flowchart showing an operation related to identification of a first volume that is performed when a process is stopped, etc. 11 is a flowchart showing operations related to identification of the volume ratio, the first volume, and the second volume that are performed when the supply of gas is stopped during the process, etc.;

The flow control device 100 according to the first embodiment of the present invention will be described with reference to Figures 1 to 4.

The flow control device 100 of one embodiment is used to supply reactive gas at a predetermined set flow rate into a chamber where plasma is generated, for example, in a semiconductor manufacturing process. Specifically, the flow control device 100 supplies reactive gas at a predetermined flow rate during the process period in which dry etching proceeds in the chamber. In addition, the flow control device 100 supplies reactive gas at a maintenance flow rate, which is the minimum flow rate required to maintain plasma in the chamber, during pauses in the process. The maintenance flow rate is a flow rate of reactive gas that prevents, for example, Coulomb crystals from being formed by fine particles (dust) in the chamber and prevents the fine particles from depositing on a substrate in the chamber during pauses.

As shown in FIG. 1, the flow control device 100 includes a fluid device consisting of a sensor and a valve provided in a flow path, and a control and calculation mechanism COM that controls the fluid device.

The fluid device is provided in the flow path and consists of a supply pressure sensor P0, a first valve V1, a first pressure sensor P1, a fluid resistance FR, a second pressure sensor P2, and a second valve V2. Each device is provided in this order from the upstream side.

Here, the fluid resistance FR is a laminar flow element, and the flow rate of gas flowing through the fluid resistance FR occurs depending on the pressure difference between the front and rear of the fluid resistance FR. The first pressure sensor P1, the fluid resistance FR, the second pressure sensor P2, and the flow rate calculation unit FC described later constitute a flow rate sensor FS that measures the flow rate of the fluid flowing through the flow path between the first valve V1 and the second valve V2. That is, the first pressure sensor P1, the fluid resistance FR, and the second pressure sensor P2 are a sensing mechanism SM that outputs an output signal according to the flow rate of the fluid flowing through the flow path, and the flow rate calculation unit FC calculates the flow rate of the fluid flowing through the flow path based on the output signal of the sensing mechanism SM. Since this flow rate sensor FS is a so-called pressure-type flow rate sensor, it has the characteristic that the lower the pressure measured by each pressure sensor, the higher the measurement accuracy of the measured flow rate. In this embodiment, the flow path in which the flow control device 100 is provided is connected to a vacuum-drawn chamber. Therefore, to reduce the pressure in the volume between the first valve V1 and the second valve V2 to below a predetermined value, the first valve V1 should be kept at a fully closed opening to reduce the amount of fluid flowing in, and the second valve V2 should be kept at a predetermined opening or higher to make it easier for the fluid in the volume to pass through the second valve V2.

The supply pressure sensor P0 is used to monitor the pressure of the gas supplied from the upstream side. Note that the supply pressure sensor P0 may be omitted in cases where it is guaranteed that the supply pressure is stable.

The first pressure sensor P1 measures the pressure of the gas (hereinafter also referred to as the first pressure) charged in the first volume VL1, which is the volume between the first valve V1 and the fluid resistance FR in the flow path.

The second pressure sensor P2 measures the pressure of the gas (hereinafter also referred to as the second pressure) charged in the second volume VL2, which is the volume between the fluid resistance FR and the second valve V2 in the flow path.

In this way, the first pressure sensor P1 and the second pressure sensor P2 respectively measure the pressure in the first volume VL1 and the second volume VL2, which are the two volumes formed by the first valve V1, the fluid resistance FR, and the second valve V2. In other words, the first pressure sensor P1 and the second pressure sensor P2 measure the pressure in the respective volumes located before and after the fluid resistance FR.

In this embodiment, the first valve V1 and the second valve V2 are of the same type, for example, a piezo valve in which a valve body is driven against a valve seat by a piezo element. The second valve V2 also corresponds to the control valve in the claims. In this embodiment, the opening of the second valve V2 is controlled by flow feedback control based on the flow rate measured by a flow sensor. On the other hand, the opening of the first valve V1 is controlled by feeding back the voltage applied to the second valve V2 so that the voltage is a predetermined constant value. In other words, the opening of the first valve V1 is controlled by feeding back information about the voltage applied to a valve other than itself.

Next, the control and calculation mechanism COM will be described in detail. The control and calculation mechanism COM is a so-called computer equipped with, for example, a CPU, memory, A/D and D/A converters, input/output means, etc., and performs at least the functions of the flow rate calculation unit FC, flow rate controller 1, first valve controller 2, and reference governor 3 by executing a program for the fluid control device stored in the memory and cooperating with various devices.

The flow rate calculation unit FC calculates the flow rate based on the measurement value indicated by the output signal of the sensing mechanism SM and a flow rate characteristic value corresponding to the measurement value. Specifically, the flow rate calculation unit FC calculates the flow rate of the fluid flowing through the fluid resistance FR based on the first pressure, which is the pressure on the upstream side of the fluid resistance FR, and the second pressure, which is the pressure on the downstream side, which are the measurement values indicated by the output signal of the sensing mechanism SM. Here, the flow rate calculation unit FC calculates the flow rate based not only on the first pressure and the second pressure, but also on the flow rate characteristic value determined according to the characteristics of the fluid resistance FR.

That is, the flow rate calculation unit FC is composed of a coefficient determination unit FC1 that determines the flow rate characteristic value, the flow path resistance, based on the first pressure and the second pressure, and an output unit FC2 that calculates the flow rate based on the first pressure, the second pressure, and the flow path resistance and outputs it to the flow rate controller 1.

For example, when the flow rate is Q, the flow path resistance is R, the first pressure is _P1 , and the second pressure is _P2 , the output section FC2 calculates the flow rate based on the formula Q = ( _P1 - _P2 ) / R. Here, the flow path resistance R changes under the influence of the first pressure _P1 and the second pressure _P2 .

The coefficient determination unit FC1 determines the flow path resistance R, which is a flow rate characteristic value, from, for example, the first pressure _P1 and the differential pressure ΔP between the first pressure _P1 and the second pressure _P2 . The coefficient determination unit FC1 may be configured to calculate the flow path resistance R from a multivariate function having the first pressure _P1 and the differential pressure as parameters, or may be configured to determine the flow path resistance R by referring to a table of the flow path resistance R, the first pressure, and the differential pressure determined in advance by an experiment or the like.

The flow rate controller 1 performs flow rate feedback control of the applied voltage, which is the manipulated variable input to the second valve V2, for example by PID control, so as to reduce the deviation between the set flow rate set by the reference governor 3 and the measured flow rate measured by the flow rate sensor.

In this embodiment, the set flow rate is a command flow rate input by the user, for example as a step function or broken line function, which is converted by the reference governor 3 into a continuous function that reflects the time delay of the measured flow rate of the flow sensor.

The first valve controller 2 controls the applied voltage to the first valve V1 so that the deviation between the control amount and the target amount is small, using the applied voltage, which is the operation amount input to the second valve V2, as the control amount. Here, the target amount is, for example, a value set by the user, and is a maintenance voltage value corresponding to the opening degree to be maintained in the second valve V2. In this embodiment, the opening degree corresponding to the maintenance voltage value is the opening degree of the second valve V2 on the fully open side, and a state in which the volume between the first valve V1 and the second valve V2 is below a predetermined pressure suitable for the operation of the flow sensor is realized by vacuuming from the chamber. In addition, the maintenance voltage value is a constant and is always set to a constant value. Normally, when controlling the opening degree of the first valve V1, information about the first valve V1 or the physical amount of the flow rate directly operated by the first valve V1 is fed back to control it, but the first valve controller 2 controls the opening degree of the first valve V1 by feeding back information about the second valve V2.

More specifically, the first valve controller 2 changes the flow rate of the fluid supplied to the flow sensor and the second valve V2 according to the magnitude of the voltage applied to the second valve V2 so that the second valve V2 is maintained at the target opening. In other words, when the voltage applied to the second valve V2 is small relative to the maintenance voltage value and the opening of the second valve V2 is smaller than the target opening, the first valve controller 2 reduces the voltage applied to the first valve V1 so as to reduce the amount of fluid supplied to the second valve V2, thereby reducing the opening of the first valve V1. Conversely, when the opening of the second valve V2 is larger than the target opening, the first valve controller 2 increases the voltage applied to the first valve V1 so as to increase the amount of fluid supplied to the second valve V2, thereby increasing the opening of the first valve V1.

Now, with reference to Figures 2 and 3, we will explain how the flow rate controller 1 and first valve controller 2 configured in this way work together. For simplicity, the influence of the reference governor 3 has been omitted in this explanation, as shown in Figure 2. In addition, as shown in Figure 3, the set flow rate is taken as an example of a case in which the set flow rate changes from a specified flow rate during the process period to a maintained flow rate during the pause period using a broken line function, and the graph shows the change over time in the voltage applied to the first valve V1 and the second valve V2.

During the process period, while a stable supply is being provided at a predetermined flow rate, the voltage V1 applied to the first valve V1 and the voltage V2 applied to the second valve V2 are each stable at a substantially constant value. The value of the voltage V2 applied to the second valve V2 during this period is substantially equal to the maintenance voltage value of the target amount input to the first valve controller 2.

Next, during the transition period between the process period and the pause period, the set flow rate input to the flow controller 1 changes significantly in a short period of time from a predetermined flow rate to a maintained flow rate, so the set flow rate becomes smaller than the measured flow rate output by the flow sensor, and a deviation occurs. For this reason, the flow controller 1 reduces the applied voltage V2 so that the opening of the second valve V2 becomes smaller so that the measured flow rate becomes smaller.

As shown in Figure 3, when the applied voltage V2 to the second valve V2 changes during the transition period, the applied voltage V2, which is the controlled amount, becomes smaller than the maintenance voltage value, which is the target amount, and a deviation occurs. Therefore, in order to eliminate this deviation, the first valve controller 2 reduces the applied voltage V1 to the first valve V1, reducing the opening of the first valve V1, and begins to reduce the amount of fluid supplied to the second valve V2.

In the early stage of the pause period, when the supply of fluid from the first valve V1 decreases, the measured flow rate measured by the flow sensor also decreases, so that the measured flow rate becomes smaller than the maintained flow rate, resulting in a deviation. For this reason, the flow controller 1 increases the opening of the second valve V2 in order to increase the flow rate of the fluid passing through the second valve V2, thereby trying to return the measured flow rate to the maintained flow rate. In addition, since the applied voltage V2 of the second valve V2 is maintained in a state smaller than the maintained voltage, the first valve controller 2 continues to reduce the applied voltage V1 to the first valve V1, thereby reducing the amount of fluid supplied to the second valve V2. This operation is repeated every control cycle, so that the applied voltage V2 to the second valve V2 continues to increase, and the applied voltage V1 to the first valve V1 continues to decrease. This tendency continues until the applied voltage V2 to the second valve V2 finally matches the target maintained voltage. Ultimately, the voltage V2 applied to the second valve V2 is maintained at the maintenance voltage, and the voltage V1 applied to the first valve V1 is maintained constant at the voltage at which the voltage V2 applied to the second valve V2 matches the target maintenance voltage.

In this way, in the early stage of the pause period, the opening of the second valve V2 changes to near full closure to achieve the maintenance flow rate, and thereafter, the opening of the second valve V2 is gradually changed to a larger value in response to the gradual change in the opening of the first valve V1. Therefore, even if the openings of the first valve V1 and the second valve V2 are changed, the flow rate of the fluid flowing out of the second valve V2 is maintained at the maintenance flow rate. In this way, even if there is a change in the set flow rate, the opening of the second valve V2 will eventually converge to the maintenance voltage value, which is the target amount. In addition, when a small flow rate is flowed, the pressure of the volume in which the flow sensor FS is installed can be reduced to a pressure at which the sensitivity and measurement accuracy are the best. On the other hand, when a large flow rate is flowed, the opening of the first valve V1 is kept large and the inflow of fluid increases, so that the value of the first pressure exceeds the pressure loss of the laminar flow element and the second valve V2, which are the fluid resistance FR, and the pressure downstream of the second valve V2, thereby achieving a large flow rate.

Next, the reference governor 3 will be explained with reference to Figures 1 and 4.

The reference governor 3 sets a set flow rate to the flow controller 1, which is a command flow rate input by the user with a time delay corresponding to the measured value indicated by the output signal of the sensing mechanism SM. Specifically, as shown in FIG. 1, the flow characteristic value used by the flow calculation unit FC of the flow sensor in each control cycle is sequentially fed back to the reference governor 3. The reference governor 3 calculates the set flow rate from the command flow rate using a coefficient corresponding to the fed back flow characteristic value, and inputs it to the flow controller 1.

Specifically, as shown in FIG. 4, the reference governor 3 acts as a first-order delay element expressed as 1/(1+RVs) when the flow resistance is R and the volume to be measured by the flow sensor is V. Here, R is not a constant but a variable with the first pressure _P1 and the differential pressure ΔP between the first pressure and the second pressure as parameters. When the reference governor 3 acts as a first-order delay element on the command flow rate in this way, the time delay of the flow sensor is reflected in the set flow rate that is output. That is, since the flow sensor is provided upstream of the second valve V2, a predetermined time delay occurs in the measured flow rate of the flow sensor with respect to the flow rate flowing to the second valve V2 by the volume, depending on the first pressure _P1 and the differential pressure ΔP. In this embodiment, a value reflecting such a time delay in the flow sensor is input to the set flow rate by the reference governor 3. As a result, even if the set flow rate is changed from a predetermined value to a flow rate equivalent to an opening degree close to full closure, such as a maintenance flow rate, it is possible to prevent an excessive deviation from occurring in the flow controller 1 and prevent the second valve V2 from being momentarily fully closed. Therefore, it is possible to supply the minimum flow rate necessary to continue generating plasma during the pause period without interruption.

In this way, according to the flow control device 100 of this embodiment, even if the set flow rate changes, the opening degree of the second valve V2 can be kept constant at the fully open side opening degree corresponding to the maintenance voltage by the control of the flow controller 1 and the first valve controller 2. Therefore, it is possible to exhaust a sufficient amount of fluid from the downstream side of the flow control device 100 and maintain the pressure in the sensing mechanism SM of the flow sensor at a low pressure at which measurement accuracy is exerted. Therefore, the flow rate accuracy of the flow control device 100 can be improved compared to the conventional method. In addition, when a large flow rate is to be flowed, the opening degree of the first valve V1 is changed to be large, the inflow of fluid increases, and the differential pressure required to realize a large flow rate can also be realized. In other words, the flow control device 100 of this embodiment can realize a low pressure state when a small flow rate is flowed, and a high pressure state when a large flow rate is flowed, so that it is possible to achieve both flow control accuracy at a small flow rate and supply capacity for a large flow rate.

Furthermore, the set flow rate set by the reference governor 3 faithfully reproduces the time delay of the flow rate sensor, which is affected by the first and second pressures, so that even if the set flow rate changes significantly, it is possible to prevent the flow controller 1 from momentarily experiencing excessive deviations and resulting in a fully closed state. This makes it possible to prevent the second valve V2 from momentarily becoming fully closed when it is closed to achieve the maintained flow rate during process pauses. Therefore, it is possible to continuously supply the reactive gas required to generate plasma into the chamber at all times, and to prevent the deposition of fine particles and the like in the chamber on the substrate.

We will now explain flow control devices in other embodiments of the present invention.

The flow control device 100 shown in FIG. 9 is equipped with a diagnoser D that identifies the size of the first volume VL1 and the second volume VL2 based on the output of each of the flow sensors FS. Note that in FIG. 9, the flow controller 1, first valve controller 2, and reference governor 3 related to the flow control described in the above embodiment are omitted. The diagnoser D in this embodiment diagnoses a flow control device 100 in which a first valve V1, a first pressure sensor P1, a fluid resistance FR, a second pressure sensor P2, and a second valve V2 are provided in this order in the flow path.

The diagnostic device D shown in FIG. 9 identifies the size of the first volume VL1 and the second volume VL2, which are the internal space formed between the first valve V1 and the fluid resistance FR, which is a part of the flow sensor FS, based on the output of the first pressure sensor P1, the second pressure sensor P2, the flow sensor FS, and a temperature sensor (not shown). Here, the fluid resistance FR is a laminar flow element in which plates PL formed along the flow direction with fine grooves are stacked as shown in FIG. 10. The sizes of the first volume VL1 and the second volume VL2 vary from the design value due to various parameters related to the fluid resistance FR as shown in FIG. 10. That is, in the past, it was thought that laminar flow was established at the upstream end face of the fluid resistance FR, so the downstream end face of the fluid resistance FR was calculated based on the upstream end position of the designed fluid resistance FR. However, in reality, the position of the fluid resistance FR is shifted from the designed position due to differences in machining equipment, etc., and the surface LF1 on which the laminar flow LF is formed is also generated a certain distance inside the end face of the fluid resistance FR. For this reason, the inventors of the present application found that when the size of the first volume VL1 is calculated based on the designed end face position of the fluid resistance FR and the seal face SL, it deviates from the actual value. Similarly, the size of the second volume VL2 also deviates from the designed size due to the positional deviation of the downstream end face of the fluid resistance FR and the occurrence of the surface LF2 where the laminar flow LF is finally broken outside the fluid resistance FR.

The diagnoser D reduces the deviation in size between the first volume VL1 and the second volume VL2 as described above in order to improve the accuracy of the control model used in the flow control device 100, for example. Specifically, as shown in FIG. 9, the diagnoser D has at least the functions of a diagnostic operation control unit D1, a first volume calculation unit D2, a second volume calculation unit D3, a volume ratio calculation unit D4, and a calibration unit D5. The configuration and operation of each unit will be described in detail below with reference to the flowcharts in FIGS. 11, 12, and 13.

First, the procedure for identifying the size of the second volume VL2 will be described with reference to the flowchart shown in FIG. 11. Note that the procedure for identifying the second volume VL2 shown in FIG. 11 is not performed during a process period in which the flow control device 100 supplies various gases to the chamber, but rather during a pause period in which the supply of various gases to the chamber is stopped, for example.

First, the diagnostic operation control unit D1 controls the first valve V1 to a fully closed state and the second valve V2 to a fully open state. In this way, only the downstream second valve V2 is kept fully open, and the gas in the first volume VL1 and the second volume VL2 in the flow control device 100 is exhausted, for example, to an exhaust flow path (step S1).

Next, the diagnostic operation control unit D1 controls the first valve V1 to be fully open and the second valve V2 to be fully closed. In other words, by opening only the first valve V1 located upstream, gas is filled into the first volume VL1 and the second volume VL2 in the flow control device 100, and pressure increase begins (step S2).

In addition, from the point when gas filling begins, the second volume calculation unit D3 starts measuring the pressure in each volume using the first pressure sensor P1 and the second pressure sensor P2 (step S3).

The second volume calculation unit D3 judges whether the pressure difference between the pressures measured by the first pressure sensor P1 and the second pressure sensor P2 has reached a maximum (step S4), and when the pressure difference reaches a maximum, the second volume calculation unit D3 starts integrating the flow rate output by the flow sensor FS (step S5). The second volume calculation unit D3 judges whether a sufficient amount of gas has been charged into the first volume VL1 and the second volume VL2, and whether the pressures measured by the first pressure sensor P1 and the second pressure sensor P2 have reached a substantially equal value on the high pressure side (step S6), and when the pressures reach a substantially equal value, the second volume calculation unit D3 ends the integration of the mass flow rate (step S7). Finally, the second volume calculation unit D3 divides the calculated integrated flow rate n by the amount of change ΔP2 in the second pressure measured by the second pressure sensor P2 during the integration period to identify the size of the second volume VL2 (step S8).

The reason why the second volume VL2 can be calculated using the above procedure is as follows. The integrated value of the flow rate of the gas that has passed through the fluid resistance FR and flowed into the second volume VL2 corresponds to the amount of change in the number of moles of the gas that has flowed in within the specified period during which the flow rate was integrated, so when the gas state equation is applied to the gas that has flowed into the second volume VL2, ΔP2·VL2=nR _G T. Here, n is the integrated value of the flow rate, R _G is the gas constant, and T is the temperature of the gas, which is treated as a constant temperature during the specified period. By transforming this gas state equation, it is found that VL2=(nR _G T)/ΔP2.

Next, the procedure for identifying the size of the first volume VL1 will be described with reference to the flowchart shown in FIG. 12. Note that the procedure for identifying the first volume VL1 shown in FIG. 12 is not performed during a process period in which the flow control device 100 supplies various gases to the chamber, but is performed, for example, during a pause period in which the supply of various gases to the chamber is stopped. Also, while the identification of the second volume VL2 utilizes the changes in gas pressure and flow rate during the pressurization process, the identification of the first volume VL1 utilizes the changes in gas pressure and flow rate during the depressurization process.

First, the diagnostic operation control unit D1 controls the first valve V1 to a fully open state and the second valve V2 to a fully closed state, and waits until the pressures in the first volume VL1 and the second volume VL2 are approximately equilibrated (step ST1). Next, the diagnostic operation control unit D1 controls the first valve V1 to a fully closed state and the second valve V2 to a fully open state, evacuating gas from the first volume VL1 and the second volume VL2, and starting decompression (step ST2).

In addition, from the point in time when the second valve V2 is opened, the first volume calculation unit D2 starts measuring the pressure in each volume using the first pressure sensor P1 and the second pressure sensor P2 (step ST3).

The first volume calculation unit D2 determines whether the pressure difference between the pressures measured by the first pressure sensor P1 and the second pressure sensor P2 has reached a maximum (step ST4). When the pressure difference reaches a maximum, the first volume calculation unit D2 starts integrating the flow rate output by the flow sensor FS (step ST5).

Next, the first volume calculation unit D2 judges whether the first volume VL1 and the second volume VL2 are sufficiently exhausted and the pressures measured by the first pressure sensor P1 and the second pressure sensor P2 are almost equal on the low pressure side (step ST6), and when the pressures become equal, the first volume calculation unit D2 ends the integration of the mass flow rate (step ST7). Finally, the first volume calculation unit D2 divides the calculated integrated flow rate n by the change amount ΔP1 of the first pressure measured by the first pressure sensor P1 during the integration period to identify the size of the first volume VL1 (step ST8). Specifically, the first volume calculation unit D2 identifies the size of the first volume VL1 based on VL1=(nR _G T)/ΔP1 derived from the gas state equation, similar to the second volume calculation unit D3. Here, n is the integrated value of the flow rate, R _G is the gas constant, and T is the temperature of the gas, which is treated as a constant temperature during the specified period.

Next, the procedure for calculating the volume ratio of the first volume VL1 to the second volume VL2 by the volume ratio calculation unit D4 will be described with reference to the flowchart in FIG. 13. Note that the procedure shown in FIG. 13 differs from that shown in FIG. 11 and FIG. 12 in that it can be performed not only during a pause period but also during a process period in which various gases are supplied into the chamber.

First, from a state where the first valve V1 and the second valve V2 are normally controlled by the first valve controller 2 and the flow controller 1 described in the above embodiment (step SP1), the diagnostic operation control unit D1 controls the first valve V1 to a fully closed state and controls the second valve V2 to a fully closed state (step SP2). Note that step SP2 may not be the result of the diagnostic operation control unit D1 controlling each valve, but may occur when the set flow rate is zero during the process period or when a fully closed command is input to the controller of each valve. In parallel, pressure measurement is started by the first pressure sensor P1 and the second pressure sensor P2 (step SP3), and the volume ratio calculation unit D4 stores the initial pressure measured by each pressure sensor (step SP4). Furthermore, the first volume calculation unit D2 and the second volume calculation unit D3 start integrating the flow rate output by the flow sensor FS, which is the flow rate of gas flowing through the fluid resistance FR (step SP5). Here, immediately after each valve is fully closed from the flow control state, a pressure difference exists within the flow control device 100, and the first pressure is higher than the second pressure.

The volume ratio calculation unit D4 determines whether the pressures measured by the first pressure sensor P1 and the second pressure sensor P2 are approximately equal (step SP6). When the first pressure decreases and the second pressure increases, and the pressures become approximately equal, the volume ratio calculation unit D4 stores the pressure as the equilibrium point pressure (step SP7), and the first volume calculation unit D2 and the second volume calculation unit D3 end the integration of the flow rate output by the flow sensor FR (step SP8).

The volume ratio calculation unit D4 calculates the ratio between the first volume VL1 and the second volume VL2 based on the stored initial pressures and the equilibrium point pressure (step SP9). Specifically, if the initial pressure measured by the first pressure sensor P1 is P1S, the initial pressure measured by the second pressure sensor P2 is P2S, and the equilibrium point pressure is PE, the volume ratio VL1:VL2 between the first volume VL1 and the second volume VL2 can be calculated based on P1S-PE:PE-P2S=VL1:VL2.

The first volume calculation unit D2 divides the integrated flow rate n by P1S-PE to calculate the size of the first volume VL1 (step SP10). Similarly, the second volume calculation unit D3 divides the integrated flow rate n by PE-P2S to calculate the size of the second volume VL2 (step SP11). More specifically, the sizes of the first volume _VL1 and the second volume VL2 are calculated based on VL1=(nR _G T)/(P1S-PE) and VL2=(nR _G T)/(PE-P2S), where R G is the gas constant and T is the gas temperature.

Furthermore, based on the size and ratio of the first volume VL1 and the second volume VL2 calculated by the first volume calculation unit D2, the second volume calculation unit D3, and the volume ratio calculation unit D4, the calibration unit D5 calibrates the parameters used in the flow sensor FR to calculate the flow rate, and calibrates various parameters used in the first valve controller 2 or the flow controller 1.

In this way, with the flow control device 100 described based on Figures 9 to 13, the size and ratio of the first volume VL1 and the second volume VL2 can be identified with values that reflect instrumental errors such as processing errors in the fluid resistance FR and the positional deviation of the surface where the laminar flow is actually formed. Therefore, since the magnitude of the action of the first volume VL1 and the second volume VL2 on the gas can be accurately obtained, it becomes possible to more accurately calculate the flow rate and set various parameters used in flow rate control. This makes it possible to realize more accurate and precise flow rate control.

Note that the start and end points of the interval for calculating the integral value of the flow rate in the procedures shown in Figures 11 to 13 are not limited to those described above. For example, the integral interval may be set to a period from a predetermined time after the differential pressure between each pressure becomes maximum to a predetermined time before each pressure becomes equilibrium. In other words, depending on the identification accuracy, the interval may be set to be shorter.

In the above embodiment, what was fed back to the first valve control unit was the applied voltage to the second valve, which is the operation amount input to the second valve, but the second valve may be provided with a displacement sensor so that the opening of the second valve can be measured, and the measured opening measured by the displacement sensor may be fed back to the first valve controller as a control amount. In this case, the target amount input to the first valve controller may be the opening value that is desired to be maintained in the second valve.

The above embodiment may be configured with the reference governor omitted, for example, as shown in the schematic diagram of FIG. 2. In this case, the command flow rate set by the user and the set flow rate will be completely the same. Conversely, as shown in the schematic diagram of FIG. 4, the first valve may be omitted, and a flow control device may be configured with a flow sensor, a second valve (control valve), a flow controller, and a reference governor. In addition, as shown in the schematic diagram of FIG. 4, the control valve is not limited to being arranged downstream of the flow sensor, but the control valve may be arranged upstream of the flow sensor. When the flow rate is arranged upstream, both or either the time delay due to the characteristics of the flow sensor itself and the phase lead due to the flow sensor being arranged upstream by the control valve may be reflected in the flow controller by the reference governor.

Furthermore, the flow rate calculation formula used in the flow rate calculation section of the flow sensor is not limited to that described in the above embodiment. For example, if the first pressure is _P1 , the second pressure is _P2 , and the flow path resistance is ^R _{, the flow rate may be calculated based on P12-P22 and} ^the flow path resistance R. Furthermore, the coefficient determined by the coefficient determination section is not limited to the flow path resistance R, and a parameter value that is necessary to calculate other types of flow rates and changes under the influence of the first pressure or the second pressure may be determined. Furthermore, the reference governor may also sequentially feed back such parameters to cause the flow rate controller to reflect the time delay in the flow rate sensor.

The flow sensor is not limited to a pressure type flow sensor, but may be of various types such as a thermal type or ultrasonic type. If the pressure to be maintained in the second valve differs depending on the type of flow sensor, the target amount input to the first valve controller can be changed appropriately so that the second valve achieves an opening degree corresponding to the pressure to be maintained in the flow sensor. Furthermore, the first and second valves are not limited to normally closed types, but may be normally open types. Since the direction of voltage application is reversed depending on the type of valve, the target amount input to the first valve controller can be set accordingly.

The present invention is not limited to a flow control device, and may be applied to, for example, a pressure control device and a concentration control device. That is, the opening of the second valve may be kept at a desired opening while the pressure of the fluid passing through the second valve is made to coincide with a set pressure by the cooperation of the first valve and the second valve. Alternatively, the opening of the second valve may be kept at a desired opening while the concentration of the fluid passing through the second valve is made to coincide with a set concentration by the cooperation of the first valve and the second valve. That is, the fluid control device according to the present invention may include a first valve provided in a flow path, a second valve provided downstream of the first valve in the flow path, a fluid sensor that measures a physical quantity of the fluid in the flow path between the first valve and the second valve, a fluid controller that controls an operation quantity input to the second valve so that the deviation between the measurement quantity measured by the fluid sensor and a set quantity is small, and a first valve controller that controls the first valve so that the deviation between the operation quantity input to the second valve or a control quantity that is the opening of the second valve and a target quantity is small. The physical quantity referred to here is a concept that includes, for example, flow rate, pressure, and concentration. Also, a fluid sensor measures either the flow rate, pressure, or concentration of a fluid.

In addition, various modifications of the embodiments and combinations of parts of each embodiment may be made without going against the spirit of the present invention.

100: Flow control device V1: First valve V2: Second valve (control valve)
FS...Flow sensor (fluid sensor)
SM: sensing mechanism FC: flow rate calculation section FC1: coefficient determination section FC2: output section P1: first pressure sensor P2: second pressure sensor 1: flow rate controller 2: first valve controller 3: reference governor D: diagnostic device D1: diagnostic operation control section D2: first volume calculation section D3: second volume calculation section D4: volume ratio calculation section

Claims (9)

A flow rate control device for use in a semiconductor manufacturing process, comprising:
A first valve provided in the flow path;
a second valve provided downstream of the first valve in the flow path;
a flow sensor for measuring a flow rate of fluid in the flow path between the first valve and the second valve;
a flow rate controller that controls an operation amount input to the second valve so as to reduce a deviation between a measured flow rate measured by the flow rate sensor and a set flow rate;
a first valve controller that controls the first valve so that a deviation between an operation amount input to the second valve by the flow rate controller or an opening degree of the second valve becomes small ,
The flow sensor,
a fluid resistance provided between the first valve and the second valve;
a first pressure sensor provided between the first valve and the fluid resistance;
A second pressure sensor provided between the fluid resistance and the second valve;
a flow rate calculation unit that calculates a flow rate of a fluid flowing through the fluid resistance based on a first pressure measured by the first pressure sensor and a second pressure measured by the second pressure sensor,
A flow control device , wherein the target amount set in the first valve controller is a constant value that maintains the opening degree of the second valve at a predetermined opening degree on the fully open side . 2. The flow control device according to claim 1 , wherein, when the opening degree of the second valve is smaller than the opening degree corresponding to the target amount, the first valve controller controls the opening degree of the first valve in a direction to decrease. the first valve is a normally open type piezo valve,
3. The flow rate control device according to claim 1, wherein the first valve controller controls the voltage applied to the first valve in a direction to increase the voltage when the controlled amount is smaller than the target amount. the first valve is a normally closed type piezo valve,
3. The flow control device according to claim 1, wherein the first valve controller controls the voltage applied to the first valve in a direction to decrease the voltage when the controlled amount is smaller than the target amount. A flow rate control method for a flow rate control device used in a semiconductor manufacturing process, the flow rate control device including a first valve provided in a flow path, a second valve provided in the flow path downstream of the first valve, and a flow rate sensor for measuring a flow rate of a fluid in the flow path between the first valve and the second valve, the flow rate control method comprising:
The flow rate sensor includes:
a fluid resistance provided between the first valve and the second valve;
a first pressure sensor provided between the first valve and the fluid resistance;
A second pressure sensor provided between the fluid resistance and the second valve;
a flow rate calculation unit that calculates a flow rate of a fluid flowing through the fluid resistance based on a first pressure measured by the first pressure sensor and a second pressure measured by the second pressure sensor,
The flow rate control method includes:
a flow rate control step of controlling an operation amount input to the second valve so as to reduce a deviation between a measured flow rate measured by the flow rate sensor and a set flow rate;
a first valve control step of controlling the first valve so that a deviation between an operation amount input to the second valve or an opening degree of the second valve in the flow rate control step and a target amount is reduced by using the operation amount input to the second valve or an opening degree of the second valve as a control amount ,
A flow rate control method , wherein the target amount set in the first valve control step is a constant value that maintains the opening degree of the second valve at a predetermined opening degree on the fully open side . A program for use in a flow control device for use in a semiconductor manufacturing process, the flow control device including a first valve provided in a flow path, a second valve provided in the flow path downstream of the first valve, and a flow sensor for measuring a flow rate of a fluid in the flow path between the first valve and the second valve,
The flow rate sensor includes:
a fluid resistance provided between the first valve and the second valve;
a first pressure sensor provided between the first valve and the fluid resistance;
A second pressure sensor provided between the fluid resistance and the second valve;
a flow rate calculation unit that calculates a flow rate of a fluid flowing through the fluid resistance based on a first pressure measured by the first pressure sensor and a second pressure measured by the second pressure sensor,
The program for the flow control device is
a flow rate controller that controls an operation amount input to the second valve so as to reduce a deviation between a measured flow rate measured by the flow rate sensor and a set flow rate;
a first valve controller that controls the first valve so as to reduce a deviation between an operation amount input to the second valve by the flow rate controller or an opening degree of the second valve as a control amount and a target amount ;
2. A program for a flow control device, wherein the target amount set in the first valve controller is a constant value that maintains the opening of the second valve at a predetermined opening degree on the fully open side . A flow rate control device for use in a semiconductor manufacturing process, comprising:
a first valve provided in the flow path;
a second valve provided downstream of the first valve in the flow path;
a fluid sensor that measures a physical quantity of a fluid in the flow path between the first valve and the second valve;
a fluid controller that controls an operation amount input to the second valve so as to reduce a deviation between a measurement amount measured by the fluid sensor and a set amount;
a first valve controller that controls the first valve so as to reduce a deviation between a control amount, which is an operation amount input by the fluid controller to the second valve or an opening degree of the second valve, and a target amount ,
The fluid sensor comprises:
a fluid resistance provided between the first valve and the second valve;
a first pressure sensor provided between the first valve and the fluid resistance;
A second pressure sensor provided between the fluid resistance and the second valve;
a flow rate calculation unit that calculates a flow rate of a fluid flowing through the fluid resistance based on a first pressure measured by the first pressure sensor and a second pressure measured by the second pressure sensor,
A flow control device , wherein the target amount set in the first valve controller is a constant value that maintains the opening degree of the second valve at a predetermined opening degree on the fully open side . A flow rate control device for use in a semiconductor manufacturing process, comprising:
a flow sensor including: a sensing mechanism provided in a flow path, which outputs an output signal corresponding to a flow rate of a fluid flowing through the flow path; and a flow rate calculation unit which calculates the flow rate based on a measurement value indicated by the output signal of the sensing mechanism and a flow rate characteristic value corresponding to the measurement value;
a control valve provided upstream or downstream of the flow sensor;
a flow rate controller that controls the control valve so as to reduce a deviation between a measured flow rate measured by the flow rate sensor and a set flow rate;
a reference governor that sets the set flow rate, which is a command flow rate with a time delay corresponding to a measurement value indicated by an output signal of the sensing mechanism, in the flow rate controller ;
The sensing mechanism includes:
Fluid resistance,
A first pressure sensor provided upstream of the fluid resistance;
A second pressure sensor provided downstream of the fluid resistance;
a flow rate calculation unit that calculates a flow rate of a fluid flowing through the fluid resistance based on a first pressure measured by the first pressure sensor and a second pressure measured by the second pressure sensor,
A flow control device , wherein a target amount set in the flow rate controller is a constant value that maintains the opening of the control valve at a predetermined opening degree on the fully open side . The flow rate calculation unit,
a coefficient determination unit that determines a flow resistance, which is the flow characteristic value, based on a first pressure and a second pressure, which are measurement values indicated by output signals of the first pressure sensor and the second pressure sensor;
an output unit that calculates the flow rate based on the first pressure, the second pressure, and the flow path resistance,
9. The flow control device according to claim 8, wherein the reference governor is configured to calculate the set flow rate based on the flow resistance determined by the coefficient determination unit and the command flow rate, and to set the set flow rate in the flow rate controller.