JP2010055500A - Flow controller and flow control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flow controller detecting a failure and performing self-diagnosis when a failure occurs in a gas flow rate measurement part while reducing a system in size without installing an additional gas flow meter. <P>SOLUTION: The flow controller has: a main pipe 10 supplying a fluid; a sensor pipe 20 connected to the main pipe 10 in parallel; a first flow rate measurement means 30 and a second flow rate measurement means 40 independently measuring a flow rate of the fluid flowing through the sensor pipe 20; a comparison circuit 50 comparing both measurement results of the first flow rate measurement means 40 and the second flow rate measurement means 40, and deciding whether the measurement results are the same or not; and a control means 60 maintaining a flow control state when the measurement results are the same, and outputting a flow rate alarm signal when both the measurement results are not the same. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a flow rate control device and a flow rate control method, and more particularly, to a flow rate control device and a flow rate control method including a main pipe that supplies a fluid and a sensor pipe connected in parallel to the main pipe.

  Conventionally, it has been known that in the case of a semiconductor manufacturing apparatus, particularly an apparatus using a special gas for device manufacturing, the flow control accuracy has a great influence on the quality of the product. A mass flow controller is generally used.

  FIG. 6 is a diagram showing a basic configuration of a conventional mass flow controller 410. In FIG. 6, a part of the gas supplied to the main pipe 310 is guided to the sensor pipe 320, and the flow rate is measured by the flow sensors 331 and 332 and the actual flow rate calculation circuit 333. The sensor tube 320, the flow sensors 331 and 332, and the actual flow rate calculation circuit 333 constitute a gas flow rate measurement unit 330. Next, the actual gas flow rate measured by the gas flow rate measuring unit 330 and the flow rate setting signal input from the outside are compared in the control main circuit 360, and the opening degree of the control valve 400 is controlled by the valve control circuit 390 by feedback control. Is automatically adjusted so that the flow rate is controlled to be the same as the set flow rate. In this case, since there is no self-check function for the abnormal flow rate, there is a problem that even if an abnormality occurs in the outlet flow rate of the mass flow controller, the abnormality cannot be detected, and many defective products may be manufactured. there were.

  Therefore, in order to improve this point and improve the abnormal flow rate detection accuracy, a method of using a mass flow controller and a mass flow meter in combination with a main gas piping system has been proposed as seen in, for example, a diffusion device. FIG. 7 is a diagram showing a configuration example of a conventional flow rate control device using such a mass flow meter together. In FIG. 7, a mass flow meter 420 is further added to the mass flow controller 410 shown in FIG. Unlike the mass flow controller, the mass flow meter is a means for measuring only the flow rate of gas flowing through the gas system, and has a function of a flow rate sensor having no flow rate control part. That is, it may be considered that the configuration is substantially the same as the gas flow rate measurement unit 330 in FIG. In this case, the flow rate value measured by the mass flow meter 420 and the flow rate value measured by the gas flow rate measurement unit 330 of the mass flow controller 410 are compared by the actual flow rate comparison circuit 350, and when there is a difference between them, the control circuit 361 Can issue a flow rate alarm and detect an abnormal flow rate to let the operator know.

As an example of such a flow rate control device having a self-diagnosis function, a diagnostic flow meter is provided in addition to a control flow meter in the main gas pipe, and an abnormality is determined when there is a difference between the measured values. 2. Description of the Related Art A flow control device connected with a determination device is known (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 5-10604

  However, in the configuration described in the above-described prior art and Patent Document 1 shown in FIG. 7, it is necessary to install a mass flow meter in the main pipe, the gas system becomes complicated, the number of parts increases, and the cost increases. There was a problem. In recent flow control devices used in semiconductor manufacturing apparatuses, many integrated flow control devices are used in order to save space. In such an integrated flow control device, there is often no sufficient space for adding a mass flow meter to the main pipe of the mass flow controller, and there are many cases where it is difficult to newly install a mass flow meter. .

  Therefore, the present invention is a flow rate control capable of performing a self-diagnosis by detecting an abnormality when there is an abnormality in the gas flow measurement unit while reducing the size of the system without adding a mass flow meter. An object is to provide an apparatus.

In order to achieve the above object, the flow rate control device (110, 110a) according to the first invention includes a main pipe (10) for supplying fluid,
A sensor pipe (20) connected in parallel to the main pipe (10);
First flow measurement means (30) and second flow measurement means (40) for independently measuring the flow rate of the fluid flowing through the sensor pipe (20);
A comparison circuit (50) for comparing the measurement results of the first flow rate measurement means (30) and the second flow rate measurement means (40) and determining whether the measurement results are equal;
Control means (60) for maintaining a flow rate control state when the measurement results are equal to each other and outputting a flow rate alarm signal when the measurement results are not equal to each other.

  As a result, a flow meter such as a mass flow meter is not newly provided in the main pipe, but the flow rate measuring means is provided in the already provided sensor pipe, so that it is not necessary to increase the space. When an abnormality occurs in the flow rate measuring means, the abnormality can be reliably detected by comparing the measurement results, and the operator can be notified of the abnormality.

A second invention is the flow rate control device (100, 100a) according to the first invention,
The first flow rate measuring means (30) and the second flow rate measuring means (40) are flow sensors (31, 32, 32) composed of resistors provided on the upstream side and the downstream side of the sensor pipe (20). 41, 42) and actual flow rate calculation circuits (33, 43) for detecting changes in the temperature distribution of the flow sensors (31, 32, 41, 42), respectively.

  As a result, the flow sensor and the actual flow rate calculation circuit can be completely independent by the first flow rate measurement unit and the second flow rate measurement unit, and even if an abnormality occurs in any one of the flow rate measurement units. The abnormality can be surely found by comparison with a normal flow rate measuring means.

A third invention is a flow control device (110, 110a) according to the first or second invention, wherein
The actual flow rate calculation circuit (33, 43) includes an actual flow rate calculation circuit (34, 44) for calculating the actual flow rate of the fluid, and a determination circuit (35, 43) for determining whether the actual flow rate is equal to a set flow rate. 45)
The control means (60) outputs the flow rate alarm signal when the determination circuit (35, 45) determines that the actual flow rate is not equal to the set flow rate.

  As a result, when the measured flow rate itself is different from the set flow rate, it is a general flow rate abnormality due to other reasons such as clogging of the pipe. You can let them know.

4th invention is the flow control apparatus (110, 110a) which concerns on either 1st-3rd invention,
A valve control circuit (90) to which a valve control signal output from the control means (60) is input;
When the actual flow rate is not equal to the set flow rate within a predetermined response time from the start of introduction of the fluid, the control means (60) outputs the valve control signal so that the actual flow rate follows the set flow rate. Output,
The valve control circuit (90) controls the flow rate of the gas by controlling a control valve (100) provided in the main pipe (10) based on the valve control signal.

  Thereby, within a predetermined response time in which overshoot and undershoot continue at the start of fluid introduction, feedback control can be executed to control the flow rate to follow the set flow rate at an early stage.

A gas flow rate control method according to a fifth aspect of the present invention includes a fluid supply step for supplying a fluid to the main pipe (10),
The flow rate of the fluid flowing through the sensor pipe (20) connected in parallel to the main pipe (10) is independently measured by the first flow rate measuring means (30) and the second flow rate measuring means (40). Flow measurement process;
A comparison step of comparing the measurement results of the first flow rate measurement means (30) and the second flow rate measurement means (40) and determining whether the measurement results are equal;
A control step of maintaining a flow rate control state when the measurement results are equal, and outputting a flow rate alarm signal when the measurement results are not equal.

  Thereby, even when there is an abnormality in the flow rate measuring means, it is possible to reliably detect the abnormal flow rate by comparing the measurement results of the independent flow rate measuring means.

A sixth aspect of the invention is a gas flow rate control method according to the fifth aspect of the invention,
The flow rate measuring step includes a step of measuring an actual flow rate of the fluid and a step of determining whether or not the actual flow rate is equal to a set flow rate,
The comparison step is performed when it is determined that the actual flow rate is equal to the set flow rate.

  As a result, the flow measurement means can be compared only when there is no abnormality in the actual flow rate itself, and when there is an abnormality in the actual flow rate itself, the comparison between the flow measurement means is performed. Needless to say, an abnormality in the flow rate can be detected at an early stage to notify the operator.

7th invention is the flow control method which concerns on 5th or 6th invention,
In the comparison step, when it is determined that the measurement results are not equal within a predetermined response time after starting the fluid supply step,
In the control step, the actual flow rate is controlled to follow the set flow rate without outputting the flow rate alarm signal.

  As a result, when the flow rate is not constant due to repeated overshoots and undershoots immediately after the start of fluid introduction, normal feedback control that causes the actual flow rate to follow the set flow rate is executed, so that the actual flow rate immediately follows the set flow rate. Thus, it is possible to inspect again whether or not a flow rate abnormality has occurred after the flow rate is stabilized.

  Note that the reference numerals in the parentheses are given for easy understanding, are merely examples, and are not limited to the illustrated modes.

  According to the present invention, it is possible to find an abnormality in the flow rate measuring means while saving space.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating an overall configuration of a flow control device 110 according to a first embodiment to which the present invention is applied. In FIG. 1, the flow control device 110 according to the first embodiment includes a main pipe 10, a sensor pipe 20, a first flow measurement unit 30, a second flow measurement unit 40, a comparison circuit 50, and a control main unit. The circuit 60, the valve control circuit 90, and the control valve 100 are included. Moreover, the flow control device 110 according to the first embodiment may include a flow rate indicator 70 and a flow rate alarm reporting unit 80 as necessary.

  The main pipe 10 is a flow path for supplying a fluid, an inlet is connected to a fluid supply source, and an outlet is connected to a target to which the fluid is supplied. The fluid may include a liquid in addition to a gas. In this embodiment, an example in which gas is used as a fluid will be described. However, the flow control device 110 according to this embodiment can be applied not only to gas supply but also to liquid supply such as a chemical solution. . Various devices or the like may be applied to the target for supplying the fluid depending on the application. For example, when supplying a gas as the fluid, a gas such as an etching device, a diffusion device, or a film forming device of a semiconductor manufacturing device is used. An apparatus for processing a semiconductor wafer using the above may be a supply target. The main pipe may be called a bypass pipe.

  The main pipe 10 may be provided with a bypass laminar flow element 11. The bypass laminar flow element 11 is an element for supplying gas uniformly to a device or the like in a laminar flow. When the fluid is a liquid, the bypass laminar flow element 11 may not be provided.

  The sensor pipe 20 is a pipe for introducing a part of the fluid flowing through the main pipe 10 and measuring the flow rate thereof. Since it is preferable that the sensor pipe 20 does not greatly change the flow rate of the main pipe 10, a thin pipe having a diameter smaller than that of the main pipe 10 may be used so as to introduce a fluid having a flow rate necessary only for measurement. For example, the sensor tube 20 may be made of stainless steel and configured as a stainless thin tube.

  The first flow rate measuring unit 30 is a unit for measuring the flow rate of the fluid flowing through the sensor tube 20, and is provided in the sensor tube 20. The first flow rate measuring means 30 includes flow sensors 31 and 32 and a first actual flow rate calculation circuit 33. The first actual flow rate calculation circuit 33 includes an actual flow rate calculation circuit 34 that calculates the actual flow rate, and a determination circuit 35 that determines whether or not the actual flow rate is equal to the set flow rate.

  The flow sensors 31 and 32 include an upstream flow sensor 31 and a downstream flow sensor 32 and are installed in the sensor tube 20. The flow sensors 31 and 32 are configured as heaters made of resistors, and are used by passing a current through the resistors. When no fluid flows through the main pipe 10, the heat of the upstream flow sensor 31 and the downstream flow sensor 32 is kept in an equilibrium state. On the other hand, when the fluid starts to flow into the main pipe 10, the fluid is introduced from the inlet of the sensor tube 20, the heat of the resistor of the upstream flow sensor 31 is taken away and moved to the downstream side, the heat balance is lost, and the temperature distribution is reduced. Change occurs. In the downstream flow sensor 32, the resistance value of the resistor changes due to this temperature change. This change is detected by the actual flow rate calculation circuit 34 of the first actual flow rate calculation circuit 33 to calculate the actual flow rate.

  The actual flow rate calculation circuit 34 is a circuit that captures changes in the resistance values of the upstream flow sensor 31 and the downstream flow sensor 32 and calculates this as a flow rate output signal. For example, a Wheatstone bridge circuit or the like is applied. May be.

  The determination circuit 35 is a circuit for determining whether the actual flow rate output signal calculated by the actual flow rate calculation circuit 34 is equal to the flow rate setting signal that is the control target value. Note that “equal” here does not mean physically equal flow rates, but means equal within the range of resolution accuracy in the flow rate control device 110, and is regarded as equal for control purposes. This means that the error is equal after including the allowable error and mechanical error. For example, regarding an error within 5%, in the case of a flow rate control device that performs control processing in which the actual flow rate and the set flow rate are equal in terms of control, the error within 5% is also included within the same range.

  The first actual flow rate calculation circuit 33 including the actual flow rate calculation circuit 34 and the determination circuit 35 may be installed at a position away from the sensor tube 20.

  The flow rate setting signal to be compared with the actual flow rate may be set by, for example, sending the flow rate setting signal input to the control main circuit 60 to the actual flow rate calculation circuit 33. Further, the determination circuit 35 may be configured to include, for example, a comparator that can compare the flow rate output signal and the flow rate setting signal. If the determination circuit 35 determines that the actual flow rate output signal is equal to the flow rate setting signal, the fluid is flowing normally at the set flow rate without any abnormality.

  However, as described in the prior art of FIG. 7, even when the determination circuit 35 determines that the actual flow rate and the set flow rate are equal and the normal state is determined, the flow sensors 31 and 32, the actual flow rate calculation circuit 34 or the determination circuit 35. Even if there is an abnormality in the electrical system, etc., even if it is electrically normal, there may be a case where the fluid actually flows at an abnormal flow rate. That is, when an abnormality occurs in the first gas flow rate measuring means 30 itself, the abnormality cannot be self-diagnosis or self-detection.

  Therefore, in the flow rate control device 110 according to the present embodiment, in addition to the first flow rate measurement unit 30, a second flow rate measurement unit 40 independent from this is further provided.

  The second flow rate measuring means 40 is provided in the sensor tube 20 independently of the first flow rate measuring means 30. Since the second flow rate measuring unit 40 is independent of the first flow rate measuring unit 30, similarly to the first flow rate measuring unit 30, the second flow rate measuring unit 40 includes flow sensors 41 and 42 and an actual flow rate calculation circuit 43. The second flow rate measuring means 40 includes a flow sensor 41 and a flow sensor 41 and an upstream flow sensor 41 and a downstream flow sensor 42, and a second actual flow rate calculation circuit 43 is an actual flow rate calculation circuit 44. And the determination circuit 45 are the same as the first flow rate measuring means 30. Further, the flow sensors 41 and 42 are installed in the sensor tube 20, and the second actual flow rate calculation circuit 43 may be installed away from the sensor tube 20 in the same manner as the first flow rate measuring unit 30. That is, the second flow rate measuring unit 40 is configured to be able to measure the flow rate of a fluid such as a gas separately from the first flow rate measuring unit 30 and is installed separately. In addition, about each component, since it is the same as that of the 1st flow measurement means 30, the description is abbreviate | omitted.

  The second flow rate measuring means 40 is not installed in the main pipe 10 with a new sensor pipe 20, but is installed in common with the sensor pipe 20 in which the first flow rate measuring means 30 is provided. Yes. This eliminates the need for providing a new space in the main pipe 10 and providing another sensor pipe 20, and makes it possible to independently measure the flow rate of the fluid by effectively using the already existing sensor pipe 20. Therefore, space saving can be achieved. For example, even when an integrated mass flow controller is used, the second flow rate measuring means 40 can be easily and at low cost using the already existing sensor tube 20. Can be installed. Further, since the existing sensor pipe 20 is used and no new pipe is installed, the second flow rate measuring means 40 can be provided in a simplified state without complicating the connection relationship.

  The flow sensors 41 and 42, the actual flow rate calculation circuit 43, and the determination circuit 44 used in the second flow rate measuring unit 40 are the same as the flow sensors 31 and 32 used in the first flow rate measuring unit 30, respectively. The same components as the flow rate calculation circuit 33 and the determination circuit 35 may be used, or different components may be used. Although it is preferable to use the same parts from the viewpoint of outputting a flow rate output signal of an actual flow rate with completely the same characteristics, a configuration using different parts may be used as long as the flow rate can be accurately measured.

  In this embodiment, the determination circuits 35 and 45 for determining whether or not the measured actual flow rate is equal to the set flow rate in both the first flow rate measuring unit 30 and the second flow rate measuring unit 40 are An example provided in the flow rate calculation circuits 33 and 43 will be described. However, the determination circuits 35 and 45 may be provided outside the actual flow rate calculation circuits 33 and 43. For example, the determination circuits 35 and 45 may be provided with the functions of the control main circuit 60 and the comparison circuit 50. The determination circuits 35 and 45 may be provided in any place as long as the actual flow rate and the set flow rate can be determined and the result can be reflected in the comparison circuit 50 and the control main circuit 60.

  In addition, the calculation in the actual flow rate calculation circuits 34 and 44 and the determination circuits 35 and 45 may be performed by a signal obtained by converting the flow rate into a voltage. For example, a voltage converted from 0 to 5 [V] is set as a set voltage, a flow output signal or a set flow signal of an actual flow rate of a fluid such as gas is set on a voltage basis, and a comparison operation is performed. Good.

  When the determination circuits 35 and 45 determine that the actual flow rate of the fluid is equal to the set flow rate, the flow rate output signals of the measurement results of the first flow rate measurement unit 30 and the second flow rate measurement unit 40 are compared with each other. 50 is output. On the other hand, in the determination circuits 35 and 45, when it is determined that the actual flow rate of the fluid is not equal to the set flow rate and there is a difference, the fluid is not supplied according to the set flow rate, and a flow rate abnormality occurs. A flow rate abnormality detection signal is output to the control main circuit 60.

  The comparison circuit 50 is a circuit for comparing the measurement result of the first flow rate measurement unit 30 with the measurement result of the second flow rate measurement unit 40 and detecting whether or not the two measurement results are equal. .

  For example, the actual flow rate of the fluid measured by the first flow rate measuring unit 30 is determined to be equal to the set flow rate by the determination circuit 35, and the actual flow rate of the fluid measured by the second flow rate measuring unit 40 is also determined by the determination circuit 45. When it is determined that the flow rate is equal to the set flow rate, if both are correctly measured, the measurement results of the first flow rate measurement unit 30 and the second flow rate measurement unit 40 should match.

  However, as described above, even if the determination results in the determination circuits 35 and 45 are normal, if either the first flow rate measurement unit 30 or the second flow rate measurement unit 40 is broken, Both values should be different. That is, in the case where only one of the first flow rate measuring unit 30 and the second flow rate measuring unit 40 is out of order, in the comparison circuit 50, the flow rate measuring units 30 and 40 that are operating normally are compared. Then, the measurement results of the flow rate measuring means 30 and 40 having the abnormality are compared with each other, so that the abnormality of the flow rate measuring means 30 and 40 itself can be found with certainty.

  As described above, the comparison circuit 50 compares the measurement result of the first flow rate measurement unit 30 with the measurement result of the second flow rate measurement unit 40, and determines whether or not the measured gas flow rates of both are equal. The first flow rate measuring unit 30 and the second flow rate measuring unit 40 are inspected to determine whether they are functioning normally.

  In the comparison circuit 50, the meaning of “equal” does not require that the flow rates are physically identical, as in the description of the determination circuits 35 and 45, and a process of being equal in control is performed. It may be equal in level. In other words, it may be equal in a range including allowable error and mechanical error within the range of accuracy that can be divided.

  Although rarely, both the first flow rate measuring means 30 and the second flow rate measuring means 40 can be considered to fail at the same time. In such a case, the same failure is caused in the same manner. It is considered extremely rare to output a flow rate output signal. Therefore, even if an abnormality occurs in both the first flow rate measuring unit 30 and the second flow rate measuring unit 40, the comparison circuit 50 detects the gas flow rate difference between the measured amounts of both the measuring units 30 and 40. It is possible.

  The comparison result between the measurement results of the first flow rate measurement unit 30 and the second flow rate measurement unit 40 in the comparison circuit 50 is output to the control main circuit 60.

  The control main circuit 60 is a control unit that performs overall control of the gas flow rate control device 110. When the comparison result signal output from the comparison circuit 50 is a signal indicating that the first flow rate measuring unit 30 and the second flow rate measuring unit 40 are normal, the control main circuit 60 controls the flow rate. The flow rate is displayed on the flow rate display 70, and a command signal for causing the valve control circuit 90 to continue the flow rate control state is output as necessary. In the case of continuing the flow control, it is not necessary to send the control command signal particularly when the command signal output to the valve control circuit 90 is not particularly required.

  On the other hand, in the control main circuit 60, the comparison result signal output from the comparison circuit 50 is not equal to the measurement result of the first flow rate measurement unit 30 or the second flow rate measurement unit 40, and any one of the flow rate measurement units 30. , 40 is a signal indicating a state in which an abnormal flow rate has occurred, a flow rate alarm signal is output to the flow rate alarm reporting unit 80 to generate a flow rate alarm. Thereby, it is possible to notify the operator of an abnormal flow rate. In addition, when a flow rate abnormality detection signal is input from the first flow rate measurement unit 30 and / or the second flow rate measurement unit 40 instead of the comparison circuit 50, a flow rate abnormality has occurred due to clogging or the like. Therefore, also in this case, a flow rate alarm signal is output and a flow rate alarm is issued.

  For example, the flow rate alarm may be issued using the flow rate alarm issuing means 80. As the flow rate alarm issuing means 80, various means for letting the operator know the flow rate abnormality may be used. For example, alarm means such as a buzzer, lighting means for blinking light, etc. may be applied as appropriate. An operator who knows the flow rate abnormality can take appropriate measures such as, for example, stopping the process and investigating the cause, and can prevent a situation where the product continues to be manufactured with the flow rate abnormality.

  The flow rate indicator 70 is a means for displaying the flow rate, and a display means for displaying the flow rate including the current measured flow rate or the past history may be applied.

  In addition, a flow rate setting signal that determines a set flow rate may be input to the control main circuit 60. This flow rate setting signal is sent to the first actual flow rate calculation circuit 33 and the second actual flow rate calculation circuit 43, and the determination means 35, 45 determines whether or not the actual flow rate is within a predetermined range from the set flow rate. Used for. Further, the flow rate setting signal may be used when performing valve control in the valve control circuit 90.

  The valve control circuit 90 is a means for controlling the opening degree of the control valve 100 and may be operated by a control command signal from the control main circuit 60. Specific feedback control may be performed by the control main circuit 60 or may be performed by the valve control circuit 90. In the feedback control, for example, the set flow rate signal and the actually measured flow rate output signal are compared, and control such that the PID operation (proportional, integral, derivative) is performed until the respective signal levels match may be executed. . In a short time after the start of introduction of the fluid into the main pipe 10, the flow rate is in a state where hunting is caused by repeated overshoot and undershoot. This is a short time of about 20 to 30 [msec], but the flow rate is usually not stable during that time. For such a predetermined response time until the control target value is reached and stabilized after the start of fluid introduction, feedback control is performed so that the flow rate follows the control target value, and control is performed so that the target value is reached early. It is preferable to do. Therefore, the actual flow rates measured by the first flow rate measuring means 30 and the second flow rate measuring means 40 do not match the set flow rates or the actual flow rates do not match within a predetermined response time after the start of fluid introduction. Even in this case, the control main circuit 60 does not recognize this as an abnormal flow rate, and performs a process of executing feedback control to make the flow rate coincide with the set flow rate. The valve control circuit 90 executes such feedback control in accordance with an instruction of a valve control signal output from the control main circuit 60. The valve control circuit 90 controls the control valve 100 by appropriately adjusting the valve opening degree of the control valve 100.

  The control valve 100 is a valve that is provided at the outlet of the main pipe 10 and adjusts the flow rate of the fluid supplied from the main pipe 10. For example, an electromagnetic valve such as a solenoid valve may be applied to the control valve 100 so as to easily control the opening degree electrically.

  As described above, according to the gas flow rate control device 110 according to the present embodiment, not only a flow rate abnormality due to a normal clogging or the like is detected, but also a flow rate abnormality based on a failure of the flow rate measuring means 30 or 40 is detected. be able to. In addition, the flow rate abnormality due to the failure of the flow rate measuring means 30 and 40 can be saved by providing the independent flow rate measuring means 30 and 40 in the existing sensor tube 20 without newly installing a flow meter such as a mass flow meter. Detection can be performed with a simple configuration while accommodating space.

  Next, a flow rate control method using the flow rate control device 110 according to the present embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating a processing flow of the flow rate control method according to the present embodiment.

  In step 100, the set flow rate signal is input to the control main circuit 60 which is a control means. Thereby, the control target value is determined. Note that the input set flow rate signal may be sent as necessary to the first actual flow rate calculation circuit 33, the second actual flow rate calculation circuit 43, the valve control circuit 90, and the like.

  In step 110, introduction of a fluid such as gas into the main pipe 10 is started. A fluid is introduced from the inlet of the main pipe 10.

  In step 120, the opening adjustment operation of the control valve 100 such as a solenoid valve is started. Thereby, feedback control for adjusting the flow rate of the fluid is started.

  In step 130, the actual flow rate of the fluid is measured by the first flow rate measuring means 30 from the fluid introduced into the sensor tube 20, and then it is determined whether or not the actual flow rate is equal to the set flow rate. Measurement of the actual flow rate of the fluid is performed, for example, by detecting a change in the resistor by the actual flow rate calculation circuit 34 from the resistors of the upstream flow sensor 31 and the downstream flow sensor 32. Then, the determination circuit 35 determines whether the actual flow rate is equal to the set flow rate.

  If it is determined in step 130 that the actual flow rate of the flow rate measuring unit 30 is equal to the set flow rate, the process proceeds to step 150. If it is determined that the actual flow rate is not equal, the process proceeds to step 160.

  In step 140, in parallel with step 130, the actual flow rate of the fluid is measured from the fluid introduced into the sensor tube 20 by the second flow rate measuring means 40, and then the actual flow rate is equal to the set flow rate. It is determined whether or not. The specific contents are the same as in step 130, and the constituent elements are merely replaced with the upstream flow sensor 41, the downstream flow sensor 42, the actual flow rate calculation circuit 43, and the determination circuit 45, and thus description thereof is omitted. To do.

  Also in step 140, as in step 130, if the actual flow rate is equal to the set flow rate, the process proceeds to step 150. If not, the process proceeds to step 160.

  In step 150, the comparison circuit 50 compares and determines whether or not the measurement result of the first flow rate measuring means 30 and the measurement result of the second flow rate measuring means 40 are equal. In step 150, if the measurement result of the first flow rate measuring means 30 is equal to the measurement result of the second flow rate measuring means 40, the process proceeds to step 180, and if not, the process proceeds to step 170.

  In step 180, the control main circuit 60 receives the signal indicating that the measurement results match from the comparison circuit 50 and the control operation is normal, and performs a process of continuing the control for maintaining the flow rate control state. End the processing flow. That is, the control main circuit 60 outputs a command signal for maintaining the control state to the valve control circuit 90, or does not particularly change the command signal because there is no change in the maintenance state. The valve control circuit 90 maintains the opening degree of the control valve 100 and keeps the fluid flow rate constant. Thereby, a normal control state can be maintained. Further, the control main circuit 60 may perform an operation of displaying the flow rate on the flow rate display means 70 simultaneously with the feedback control. After the processing flow ends, the processing flow is repeated from the beginning.

  Returning to Step 130 and Step 140, if the actual flow rate is not equal to the set flow rate in the first flow rate measurement unit 30 or the second flow rate measurement unit 40, a flow rate abnormality detection signal is output to the control main circuit 60. The process proceeds to step 160.

  In step 160, it is determined in the control main circuit 60 whether or not it is within a predetermined response time from the start of gas introduction in step 110. This is because immediately after the start of control, overshoot and undershoot are repeated near the target value, and a predetermined response time is required until the target value is followed. Is to distinguish. The response time may be on the order of a level of 20 to 30 [msec], for example.

  In step 160, when it is still within the predetermined response time from the start of fluid introduction, the process returns to step 120, and the process flow is repeated from the stage when the opening adjustment operation of the control valve 90 is started. On the other hand, if the predetermined response time has elapsed since the introduction of the fluid, it is considered that a flow rate abnormality due to clogging or the like has occurred, so the routine proceeds to step 190.

  In step 190, the control main circuit 60 outputs a flow rate abnormality alarm signal, operates the flow rate alarm reporting means 80, and notifies the operator of the flow rate abnormality. Then, the processing flow is ended, and after the end, the processing flow is repeated from the beginning.

  Return to step 150. In step 150, when the flow rate measurement result by the first flow rate measurement means 30 and the flow rate measurement result by the second flow rate measurement means 40 are not equal, the first flow rate measurement means 30 or the second flow rate measurement means. Since it is considered that an abnormality has occurred in one or both of 40, the comparison circuit 50 outputs the comparison determination result to the control main circuit 60 and proceeds to step 170.

  In step 170, as in step 160, it is determined in the control main circuit 60 whether or not it is within a predetermined response time from the start of fluid introduction in step 110. As described in Step 160, the response time may be, for example, about 20 to 30 [msec].

  If it is determined in step 170 that the timing is within a predetermined response time range from the start of fluid introduction, the process returns to step 120 and the process flow is repeated from the opening adjustment operation start stage of the control valve 90. On the other hand, when it is determined that the predetermined response time has passed from the start of fluid introduction and the normal operation stage has been entered, the routine proceeds to step 190.

  In step 190, as described above, the control main circuit 60 outputs a flow rate abnormality alarm signal, operates the flow rate alarm reporting means 80, issues a warning, notifies the operator of the flow rate abnormality, and ends the processing flow. After the processing flow ends, the processing flow is repeated from the beginning.

  Thus, according to the flow rate control method according to the present embodiment, the control state is continued when the flow rate is normal, and the flow rate alarm is issued when a flow rate abnormality is detected. A flow rate alarm can be issued not only when a flow rate abnormality is detected by the flow rate measuring means 30, 40 but also when the measurement result of the first flow rate measuring means 30 and the measurement result of the second flow rate measuring means do not match. Further, it is possible to detect an abnormality in the flow rate based on an abnormality in the flow rate measuring means 30 and 40 itself. As a result, self-diagnosis of the flow control device 110 and highly accurate flow rate abnormality detection are possible.

  FIG. 3 is a diagram showing a processing flow of a conventional mass flow controller as a reference for comparison. This corresponds to the processing flow performed in the mass flow controller shown in FIG. In FIG. 3, for comparison, the same step numbers are used for the same steps as those in FIG. 2, and steps that are similar but have different contents or significance are one of the similar steps. Step numbers with different numbers are added. Further, the reference numerals of the constituent elements in the following description are attached corresponding to FIG.

  In FIG. 3, in step 100, a set flow rate signal is input. Since this is an input of the control target value, it is the same step as the flow rate control method according to the present embodiment.

  In step 110, gas introduction into the main pipe 310 is started, which is also a common step performed for gas supply.

  In step 120, the opening adjustment operation of the control valve 400 is started. This is a common step for starting feedback control.

  In step 135, the control main circuit 360 determines whether or not the actual flow rate measured by the gas flow rate measuring unit 330 is equal to the set flow rate. This is a determination for performing feedback control, and does not have an effect of detecting an abnormal flow rate.

  In step 135, when the set flow rate that is the target value and the actual flow rate are different, the process returns to step 120, and the feedback control of the opening adjustment operation of the control valve 400 is repeated until the actually measured value becomes equal to the target value. Then, when the actually measured amount becomes equal to the set flow rate, the process proceeds to Step 180. However, when the flow rate abnormality occurs and the actually measured amount is different from the set flow rate, the process of repeating Step 120 and Step 135 is repeated. There is no choice but to detect an abnormal flow rate.

  In step 180, the control main circuit determines normal operation in 360, maintains the control state, and ends the processing flow.

  Thus, in the processing flow of FIG. 3, even when a flow rate abnormality occurs, only the feedback control is repeated endlessly, and the flow rate abnormality cannot be detected.

  FIG. 4 is a diagram showing a processing flow of a conventional mass flow controller having an alarm function for reference comparison. In the mass flow controller shown in FIG. 6, this corresponds to the processing flow performed when the alarm function is installed in the control main circuit 360. In FIG. 4, for comparison, the same steps as those in FIG. 2 are given the same step numbers. Further, the reference numerals of the constituent elements in the following description are attached corresponding to FIG.

  Since the set flow rate signal input, the gas introduction, and the control valve in steps 100 to 120 are the same as the processing flow in FIGS. 2 and 3, the description thereof is omitted.

  In step 130, the actual flow rate control main circuit 360 determines whether the actual flow rate is equal to the set flow rate. This is a process performed by the determination circuits 35 and 45 of the first flow rate measurement unit 30 and the second flow rate measurement unit 40 in the flow rate control apparatus according to FIG. The processing content is almost the same as step 130 in FIG.

  If it is determined in step 130 that the actual flow rate is equal to the set flow rate, the process proceeds to step 180, the control state is maintained, and the processing flow is terminated. On the other hand, if it is determined in step 130 that the actual flow rate is not equal to the set flow rate, the process proceeds to step 160.

  In step 160, it is determined in the control main circuit 360 whether or not it is within a predetermined response time from the gas introduction. This is because the flow rate is not stable in the initial state of the start of gas introduction, so that feedback control is continued, and the processing content is the same as that of step 160 in FIG.

  In step 160, when it is within the predetermined response time, the process returns to step 120 and the process flow is repeated from the opening adjustment operation of the control valve 400. This operation is also the same as steps 160 to 120 in FIG.

  On the other hand, if the predetermined response time has passed in step 160, the actual flow rate does not become equal to the set flow rate even when the control is stable. And the processing flow ends. This process is also the same as the operation from step 160 to step 190 in FIG.

  In this manner, at first glance, the processing flow shown in FIG. 4 has an alarm function for detecting an abnormal flow rate, and appears to have no problem, but at the time of comparison determination between the actual flow rate and the set flow rate in step 130, the flow detection system or If there is an abnormality in the control system and the operation is such that the apparent signals match, even if an abnormality in the flow rate actually occurs, it cannot be detected as an abnormality. That is, the processing flow of FIG. 4 is the independent flow rate of steps 140, 150, and 170 in the processing flow of the flow rate control method according to the present embodiment of FIG. Since there is no function and process for performing the self-diagnosis of the flow rate measurement means 30 and 40 (FIG. 1) by measuring the flow rate measurement means 2 of 2 and comparing the measurement results of the actual flow rates, the gas flow rate measurement unit 330, the controller An abnormality of the circuit 360 cannot be detected.

  Comparing the processing flow of the flow rate control method according to this embodiment shown in FIG. 2 with the conventional processing flows of FIGS. 3 and 4, the flow control method according to this embodiment has a highly accurate flow rate abnormality detection function. You can see that

  In the second embodiment, an example in which the flow control device 110 according to the first embodiment is applied to a gas flow mass flow controller 110a to constitute a dry etching device will be described. FIG. 5 is a diagram illustrating the overall configuration of the dry etching apparatus according to the second embodiment.

  The dry etching apparatus according to the second embodiment includes a gas introduction valve 120, a mass flow controller 110a, a gas line filter 130, a regulator 140, and a gas extraction valve 150 in a gas supply system. In addition, the dry etching apparatus includes a chamber 200, and includes an electrode unit 180 and a stage 190 in the chamber 200, and a wafer W is placed on the stage 190. Further, the dry etching apparatus includes an electrode head unit 170 for generating radical gas and an RF (Radio Frequency) oscillator 170 outside the chamber 200, and includes a main valve 210, a pressure control valve 220, and a vacuum exhaust system. And a vacuum pump 230. In addition, the dry etching apparatus includes a stage temperature controller 240 for adjusting the temperature of the stage 190 and a ground wire 250 outside the chamber 200.

  In the etching process of the dry etching apparatus according to the second embodiment, the wafer W is placed on the stage 190, and the inside of the chamber 200 is adjusted to an appropriate degree of vacuum by the vacuum pump 230, the pressure control valve 220, and the main valve 210. This is performed by introducing radical-activated etching gas into the chamber 200 while the stage 190 is adjusted to an appropriate temperature by the temperature controller 240.

In the gas supply, the gas extracted by opening the gas extraction valve 150 is roughly adjusted in flow rate by the regulator 140, and further, the gas purified through the gas line filter 130 is adjusted in flow rate with high accuracy by the mass flow controller 110a. This is done by opening the gas introduction valve 120. Various gases for dry etching may be used as the gas. For example, sulfur hexafluoride (SF ₆ ) gas, carbon tetrafluoride (CF ₄ ) gas, or the like may be used.

  Gas is supplied to the electrode head unit 160, a high frequency is applied by an RF oscillator, the gas is ionized / radicalized by plasma, and the ionized / radicalized gas is supplied from the electrode unit 180 into the chamber 200.

  The activated gas reacts with the wafer W, and the wafer W is etched by a chemical reaction. In this way, reactive ion etching is performed. In this case, control of the gas supply flow rate is extremely important, and appropriate reactive ion etching is performed for the first time by supplying the gas at the set flow rate to the electrode head portion 60. Therefore, when a gas flow rate abnormality occurs, the wafer W cannot be properly etched, and a defective product is manufactured. In particular, FIG. 5 shows a sheet processing apparatus. However, in a processing apparatus that processes a plurality of wafers W at a time, the yield is greatly reduced.

  From this point of view, the detection of the abnormal flow rate is extremely important in the semiconductor manufacturing process, and by using the mass flow controller 110a according to the present embodiment, it is possible to detect the abnormal flow rate with high accuracy and to notify the operator. Thus, the yield of semiconductor manufacturing can be improved.

  Note that although an example of reactive ion etching has been described with reference to FIG. 5, a dry etching apparatus that supplies reactive gas to the chamber 200 and performs reactive gas etching may be used. In this case, the RF oscillator 170, the electrode head unit 160, and the electrode unit 180 are not necessary, and the apparatus configuration may be such that the reaction gas is directly supplied into the chamber 200.

  In addition, when performing wet etching, it can be configured as a wet etching apparatus that requires a predetermined amount of liquid to be supplied at a set flow rate by changing the fluid into an etching solution and configuring the apparatus as a wet etching apparatus. .

  In addition, not only a semiconductor device but also a flow control device and a flow control method according to the present embodiment can be applied to a device that needs to supply a predetermined amount of fluid according to a set flow rate.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

1 is an overall configuration diagram of a flow control device 110 according to a first embodiment. It is the figure which showed the processing flow of the flow control method concerning Example 1. FIG. It is the reference comparison figure which showed the processing flow of the conventional mass flow controller. It is the reference comparison figure which showed the processing flow of the conventional mass flow controller which gave the alarm function. FIG. 4 is an overall configuration diagram of a dry etching apparatus according to a second embodiment. FIG. 6 is a basic configuration diagram of a conventional mass flow controller 410. It is the figure which showed the structural example of the conventional flow control apparatus which used the mass flow meter together.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Main piping 11 Bypass laminar flow element 20 Sensor pipe | tube 30 1st flow measurement means 31, 32, 41, 42 Flow sensor 33 1st actual flow calculation circuit 34, 44 Actual flow calculation circuit 40 2nd flow measurement means 43 Second actual flow rate calculation circuit 50 Comparison circuit 60 Main control circuit 70 Flow rate indicator 80 Flow rate alarm issuing means 90 Valve control circuit 100 Control valve 110, 110a Flow rate control device 120 Gas introduction valve 130 Gas line filter 140 Regulator 150 Gas extraction Valve 160 Electrode head part 170 RF oscillator 180 Electrode part 190 Stage 200 Chamber 210 Main valve 220 Pressure control valve 230 Vacuum pump 240 Stage temperature controller 250 Ground wire

Claims (7)

Main piping for supplying fluid;
A sensor pipe connected in parallel to the main pipe;
First flow measurement means and second flow measurement means for independently measuring the flow rate of the fluid flowing through the sensor tube;
A comparison circuit for comparing the measurement results of the first flow measurement means and the second flow measurement means and determining whether the measurement results are equal;
And a control means for maintaining a flow rate control state when the measurement results are equal, and outputting a flow rate alarm signal when the measurement results are not equal.   The first flow rate measuring unit and the second flow rate measuring unit include a flow sensor composed of resistors provided on the upstream side and the downstream side of the sensor tube, and an actual detection unit for detecting a change in temperature distribution of the flow sensor. The flow rate control device according to claim 1, further comprising a flow rate calculation circuit. The actual flow rate calculation circuit includes an actual flow rate calculation circuit that calculates an actual flow rate of the fluid, and a determination circuit that determines whether the actual flow rate is equal to a set flow rate,
3. The flow rate control device according to claim 1, wherein the control unit outputs the flow rate alarm signal when the determination circuit determines that the actual flow rate is not equal to the set flow rate. 4. A valve control circuit to which a valve control signal output from the control means is input;
The control means outputs the valve control signal to cause the actual flow rate to follow the set flow rate when the actual flow rate is not equal to the set flow rate within a predetermined response time from the start of introduction of the fluid,
The said valve control circuit controls the flow volume of the said gas by controlling the control valve with which the said main piping was provided based on the said valve control signal. The flow control device described. A fluid supply process for supplying fluid to the main piping;
A flow rate measuring step of independently measuring the flow rate of the fluid flowing through the sensor pipe connected in parallel to the main pipe by the first flow rate measuring means and the second flow rate measuring means;
A comparison step of comparing the measurement results of the first flow measurement means and the second flow measurement means and determining whether the measurement results are equal;
A control step of maintaining a flow rate control state when the measurement results are equal to each other, and outputting a flow rate alarm signal when the measurement results are not equal to each other. The flow rate measuring step includes a step of measuring an actual flow rate of the fluid and a step of determining whether or not the actual flow rate is equal to a set flow rate,
The flow rate control method according to claim 5, wherein the comparison step is executed when it is determined that the actual flow rate is equal to the set flow rate. In the comparison step, when it is determined that the measurement results are not equal within a predetermined response time after starting the fluid supply step,
The flow rate control method according to claim 5 or 6, wherein in the control step, the actual flow rate is controlled to follow a set flow rate without outputting the flow rate alarm signal.

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