JPH06194203A - Mass flow controller with abnormality diagnosis function and its diagnosis method - Google Patents

Abstract

PURPOSE:To enable the presence of abnormality at a sensor part to be diag nosed by obtaining reference characteristics data set, in advance, stepwise over the entire flow range, so as to detect difference between the nominal reference pressure signal and the pressure signal actually detected. CONSTITUTION:Using, firstly, a diagnosis function part B, reference characteristics data corresponding to each flow set value is obtained and stored in a reference pressure signal storing part 16 and a reference data staring part 18. To diagnose presence of abnormality, a turn-over switch 14 is switched to a diagnosis mode on the contact b side, and a diagnosis flaw value is set with a key 30a at a console part C, so that, among pre-stored data in the reference data storing part 18, reference pressure signal corresponding to flow setting signal is directly read, and then outputted to a pressure signal comparison part 20, and also to a comparison part 11. Meanwhile, from the actual pressure signal measured by a pressure sensor 26 on an outflow path 4, corresponding pressure signal is obtained, and it is compared with the reference pressure signal at the pressure signal comparison part 20. Then, if it is out of a permitted range, abnormality signal is outputted to an alarm display means 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass flow controller for controlling a mass flow rate of a fluid used in a semiconductor manufacturing process, and more particularly to a mass flow controller having a function of self-diagnosing whether or not an abnormality occurs in a flow rate sensor section.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing an example of a conventional mass flow controller. In this mass flow controller, a fluid inflow path 50, a bypass flow path 51 in which the fluid in the inflow path 50 is separately flowed in parallel, a sensor flow path 52, and the fluids in the bypass flow path 51 and the sensor flow path 52 join together. Outflow path 53 and flow control valve 54 provided in the middle of this outflow path 53
And an amplifier circuit 56 that amplifies the detection signal of the sensor unit 55,
This amplified detection signal and preset mass flow rate setting signal
57 and a comparison control unit 58 which outputs a drive signal to the flow control valve 54. Here the sensor section 55
For example, a coil 62 and a coil 63 are wound around the outer peripheral surface of a thin stainless steel tube 52 having an inner diameter of about 0.5 mm, and the coil 63 is wound downstream of the coil 62. The bridge circuit 60 is usually composed of two bridge circuits. Further, this mass flow controller may take out the amplified detection signal from the sensor unit 55 as an output signal and display the mass flow rate externally.

In recent years, with the progress of semiconductor manufacturing processes, the kinds of fluids flowing to the mass flow controller have been increasing and diversifying. If, for example, a gas having corrosiveness or a gas that is easily decomposed by heat is allowed to flow through the mass flow controller for a long period of time, the gas is decomposed in the stainless steel thin tube used in the sensor part of the mass flow controller, and solid matter is generated. And the like, which adheres to the inner wall of the thin tube, or reacts with other gas to react and deposits in the thin tube, which may cause clogging in the thin tube. As a result, the sensitivity of the sensor part changes, and the flow rate flowing through the sensor part decreases even though a sufficient amount of fluid is flowing in the bypass channel, and the actual flow rate increases relative to the set mass flow rate. . However, conventionally, since the mass flow controller does not have a means for detecting clogging of the thin tube of the sensor section, it is the actual situation that this abnormality is discovered only after the state of the semiconductor manufacturing process changes.

Due to such a problem, recently, a mass flow controller having an abnormality diagnosing function by the following method has been proposed. For example, one method is
As disclosed in Japanese Patent No. 014, a sensor tube for flow rate measurement and a sensor tube for checking with a large inner diameter are provided separately, and the output signal values of both sensor parts are compared by a comparator, and the difference is constant. When the value exceeds the value, it is determined that an abnormality such as clogging has occurred in the flow rate measuring sensor tube and an alarm is issued. Another method is disclosed in Japanese Patent Laid-Open No. 63-48422.
As disclosed in the publication, the control circuit is provided with a valve opening setting means for setting the valve opening of the control valve to a constant value, and when diagnosing whether there is an abnormality, it is switched to the diagnostic circuit and the valve opening setting means is used. The control valve is temporarily fixed to a predetermined valve opening according to the input reference value, a predetermined flow rate is obtained, and then the reference value and the actual output signal of the flow sensor are compared, and an error occurs depending on the difference between the two. There was a method of determining the presence or absence of.

[0005]

However, in the former method of the above-mentioned prior arts, the checking sensor also changes with time at the same time, and it is necessary to mechanically add a checking sensor tube and a sensor section. Therefore, there is a problem that the flow controller itself becomes large and the assembly and the like becomes complicated. In the latter method, if a predetermined reference value (valve drive signal) is given to the control valve to fix it to a predetermined valve opening, this reference value is compared with the sensor output signal to determine whether there is an abnormality. Can not be diagnosed. That is, since it is assumed that the flow rate is constant, the diagnosis operation is not performed at a flow rate other than the predetermined flow rate determined by the reference value, for example, the flow rate currently controlled. Furthermore, there is a problem that the solenoid valve used as a flow rate control valve or the actuator of the piezoelectric element has hysteresis, and the opening is different even when the valve is operated from the closed state and when it is operated from the open state. It was Moreover, when the pressure at the inlet of the valve fluctuates, there is a problem that the flow rate changes for the same degree of opening and an abnormality cannot be diagnosed. In a mass flow controller that controls the flow rate by changing it stepwise, not only the span drift in which the slope of the graph showing the relationship between the flow rate of the sensor section and the output signal changes but also the zero point drifts relatively. It happens a lot. In other words, as described above, it is not possible to calibrate the relationship between the flow rate and the sensor output over the entire other flow rate range by diagnosing or calibrating at only one point. That is, although it is necessary to diagnose whether or not there is an abnormality with as many control flow rates as possible, the above-mentioned prior art cannot flexibly deal with fine designation of the diagnostic flow rate. Also, the flow rate range that can be diagnosed was limited.

In view of the above, the present invention solves the above-mentioned problems, and an arbitrary designated flow rate (diagnostic flow rate) within the entire flow rate control range.
Then, an object of the present invention is to provide a mass flow controller having a function capable of diagnosing whether or not there is an abnormality such as clogging of a sensor unit even if the pressure at the inlet of the mass flow controller fluctuates.

[0007]

According to the present invention, pressure detecting means is provided on the downstream side of a flow rate control valve of a mass flow controller, and a pressure signal corresponding to the flow rate setting signal is measured stepwise in advance over the entire flow rate setting range. Means for storing these as a reference pressure signal, means for inputting a flow rate set value in use, means for reading a reference pressure signal corresponding to this flow rate set value, this read reference pressure signal, and the pressure at this time Comparing means for comparing the pressure signal actually output from the detecting means by considering the allowable amount, and display means for displaying an abnormal signal according to the comparison result are provided. Further, a correction means for linearizing the reference characteristic data composed of the flow rate setting signal and the reference pressure signal is further provided, and the pressure signal actually output is also linearly corrected to obtain the corrected reference pressure signal and the corrected reference pressure signal. The actual pressure signal may be compared as above.

[0008]

In the mass flow controller with an abnormality diagnosing function according to the present invention, the pressure of the reaction chamber on the downstream side of the mass flow controller is kept substantially constant, and the flow rate is changed stepwise relatively frequently to control the fluid. It is suitable for use in various semiconductor manufacturing processes. Reference characteristic data composed of a reference flow rate setting signal and a reference pressure signal, which are set stepwise in advance over the entire flow rate range, are obtained. This will be used later when diagnosing the presence or absence of abnormality. On the other hand, in a normal use state, the separately set mass flow rate setting signal and the detection signal of the sensor section are compared and controlled by the comparison control section, and the valve drive signal is output to the flow rate control valve. At this time, the output value from the pressure detecting means changes depending on the pressure loss of the pipe from the pressure detecting means to the reaction chamber. That is, the inside of the reaction chamber is in a substantially vacuum state (10-1 to 10-3
Torr) and the piping to the reaction chamber is designed to cause pressure loss. Since this pressure loss is sufficiently larger than the pressure loss due to the increase / decrease of the process gas in the reaction chamber, the relationship between the flow rate and the pressure loss is kept almost constant. Here, when the sensor section starts to be clogged, the pressure loss of the sensor section increases and the flow rate flowing to the bypass side increases. Although the flow rate through the flow rate control valve has not actually changed, the comparison control unit increases the valve drive signal so as to eliminate the deviation between the flow rate setting signal and the sensor signal, so the flow rate increases more than necessary. At the same time, the pressure value of the pressure detecting means increases. In other words, when clogging occurs, a deviation will occur between the desired reference pressure signal and the actual pressure signal detected by the pressure detection unit. The present invention provides an alarm when the deviation exceeds the allowable range.

Further, according to the present invention, the flow rate value for diagnosing the presence or absence of abnormality can be freely set at regular intervals or when the control flow rate is changed, and the reference pressure signal corresponding to this flow rate setting signal is taken out, This is compared with the actual pressure signal, and when the result is out of the allowable range, an alarm is displayed by a lamp or sound. Here, since the reference characteristic data consisting of the flow rate setting signal and the reference pressure signal is taken stepwise over the entire flow rate range and stored in series, an arbitrary value can be selected as the flow rate setting value at the time of diagnosis. However, the reference pressure signal corresponding to this flow rate setting value can be taken out. Further, the reference pressure signal corresponding to the flow rate value that is not stored or the flow rate value below the decimal point can be calculated, and the diagnosis can be repeatedly performed over the entire flow rate range. Even if the pressure at the inlet changes, if the pressure inside the chamber is constant, the pressure at the outlet side of the mass flow controller is constant, and the abnormality diagnosis can be accurately performed. From the above, there is flexibility in setting the flow rate value for diagnosis, and it is possible to diagnose whether there is an abnormality in the flow rate that is currently controlled in the in-line state.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a main part of a mass flow controller with an abnormality diagnosis function according to an embodiment. The mass flow controller with an abnormality diagnosing function of the present embodiment is composed of a mass flow controller portion A (shown by ...), a diagnostic function portion B (shown by-), and a console portion C (shown by -...-). The diagnostic function part B and the console part C are added to the mass flow controller part A (however, in FIG. 1, a part of the comparison control part is included in the diagnostic function part). However, it is not limited that these components are provided integrally or close to each other.
First, the mass flow controller portion A will be described. In FIG. 1, a fluid to be measured, for example, a gas body, flows from an inlet of a mass flow controller through an inflow passage 1 and is divided into parallel bypass passages 2.
And the sensor flow path 31 at a predetermined ratio. Furthermore, the gas that has passed through the bypass flow passage 2 and the sensor flow passage 31 merges again and flows through the outflow passage 4, and the flow rate is controlled by a flow control valve 5 provided in the outflow passage 4, and the gas flows out from the outflow port. . A pressure sensor 26 serving as pressure detecting means is provided on the downstream side of the flow control valve 5. The pressure sensor 26 may be provided in the mass flow controller or may be provided in an external pipe, and the installation location is not limited.

The sensor flow path 31 is provided with a sensor section 3 for outputting a mass flow rate signal according to the flow rate. Normally, the upstream coil 32 and the downstream coil 33 have the same electric resistance value and a constant current flows. Generates the same amount of heat as. When the gas flows through the sensor channel 31, the gas takes away the amount of heat generated in the upstream coil 32,
The gas whose temperature has risen warms the downstream coil 33. As a result, the downstream coil 33 is more upstream than the upstream coil 32.
The temperature becomes higher, and the electric resistance value also varies accordingly. When this difference is taken out as an unbalanced voltage via the bridge circuit 6, the mass flow rate of the gas flowing in the sensor flow path 31 has a relationship with this unbalanced voltage. Therefore, the mass flow rate is detected by detecting the unbalanced voltage. Can be measured. The detected unbalanced voltage e passes through the amplifier circuit 7 and the A / D converter 8 and is amplified to become the mass flow rate signal f, which is the comparison unit 11
Entered in. On the other hand, the mass flow rate setting signal g corresponding to the desired control flow rate is externally input to the comparison section 11 via the a contact of the changeover switch 14. Therefore, the comparison unit 11 compares the mass flow rate signal f detected by the sensor unit with the mass flow rate setting signal g and outputs a signal h proportional to this difference to the valve drive voltage determination circuit 12. In the valve drive voltage determination circuit 12, the above signal h
Based on the current drive signal, PID control is performed by the built-in valve drive voltage determination program, and a valve drive signal (hereinbelow, referred to as voltage) V is output. And D / A
It is input as a drive voltage to the actuator of the flow control valve 5 via the converter 13, and as a result, the flow control valve 5 is driven and the valve opening changes so as to reduce the above difference. In this way, the flow rate control valve 5 is controlled so that the valve opening degree is adjusted and the control flow rate according to the mass flow rate setting signal g is maintained. At this time, the output signal of the pressure sensor 26 outputs a voltage corresponding to the pressure loss of the pipe from the outlet of the mass flow controller to the chamber connected to the downstream side, and changes with the flow rate change.

Next, the diagnostic function portion B will be described with reference to FIGS. FIG. 2 is an outline of a flowchart for setting reference characteristic data in the initial state. FIG. 3 shows a relationship diagram between the flow rate setting value and the pressure signal. FIG. 4 shows a characteristic data diagram of a flow rate setting signal and a pressure signal in which the flow rate setting value of FIG. 3 is replaced with a reference flow rate setting signal. FIG. 5 shows a corrected characteristic data diagram in which the scale of the pressure signal in FIG. 4 is converted and the diagram is linearized. In addition, in FIG. 4 and FIG. 5, the reference value is shown by a thin line, and the actual measurement value measured by the actual sensor unit is also shown by a solid line.

First, for each mass flow controller using the diagnostic function section B, the flow rate setting signal and pressure signal corresponding to each flow rate setting value are set to 1 in advance in the initial state.
The reference characteristic data corresponding to the pair 1 is obtained. At this time, the changeover switch 14 is changed over from the a contact to the b contact, and the setting signal automatic generation circuit 15 is changed. The automatic setting signal generation circuit 15 has a built-in program for performing the flow rate setting stepwise over the entire flow rate range from 0% to 120% with a margin. This allows each flow rate set value i% to be generated stepwise at arbitrary intervals, and the flow rate setting signal ki is generated corresponding to this flow rate set value i%. This signal k is substantially the same as the mass flow rate setting signal g described above, but k has a corresponding signal over the entire flow rate range from k0 to k120 (2b in FIG. 2). Then, when the generated flow rate setting signal ki is input to the comparison section 11, the mass flow rate signal f from the sensor section 3 is compared and the valve drive voltage Vi is output via the valve drive signal determination circuit 12. The pressure signal Vp at this time is measured by the pressure sensor (see FIG.
2c) This is stored in the reference pressure signal storage unit 16. At the same time, the pressure signal Vp is also stored in the reference data storage unit 18. Here, the flow rate setting value i is the flow rate setting signal ki
Alternatively, the flow rate setting signal may be omitted. Further, the pressure signal Vp may be directly output to the linearization circuit described below without being stored in the reference pressure signal storage unit 16 as a whole.

Further, as in the present embodiment, the reference pressure signal V
Input p to the reference pressure signal linearization circuit 17, scale-convert it so that 100% of the flow rate setting value corresponds to the flow rate setting signal 5V, and linearize the flow rate setting signal and the reference pressure signal as shown in FIG. Is desirable. The corrected pressure signal vp obtained by linearly correcting in this way is also stored in the reference data storage unit 18. Corresponding to 0 to 120% of the above operations, k0 to k120
By repeating (2f, g in FIG. 2), 121 reference characteristic data corresponding to the flow rate setting signals k0 to k120, the reference pressure signals V0 to V120, and the corrected pressure signals v0 to v120 are stored in the reference data storage unit. Stored in 18 (2 in FIG. 2)
e). Further, although the circuit 25 for linearly correcting the pressure signal actually output from the pressure sensor is provided, this may also serve as the linearization circuit 17. With this data, FIGS. 3, 4, and 5 can be obtained. In FIG. 4, the actual output value of the pressure sensor unit is also shown in addition to the diagram of this reference characteristic data. In the present invention, the reference value shown by the thin line is actually measured by the sensor unit shown by the solid line. The values are overlapped and compared, and it is determined whether or not there is an abnormality by checking whether or not this difference is within an allowable value.

The reference pressure signal linearization circuit 17 has a built-in program for correcting the relationship between the reference pressure signal V and the flow rate setting signal k through scale conversion or the like for linearization. Is also included. By doing so, the flow rate set value that is not stored, the flow rate set value below the decimal point, etc. can be calculated and the corresponding value can be obtained and compared on the linearized data. The linearized data after correction is shown in FIG. 5 together with the actual measurement values. Of course, this linearized data is used as a reference value and this is compared with the linearly corrected actual measurement values to determine the presence or absence of abnormality. Good. The data reading unit 19 displays the flow rate value X when the diagnostic mode described later is set.
It has a function of reading out the reference pressure signal VX corresponding to. If the relationship between the corrected pressure signal v and the flow rate setting signal k is displayed on the external monitor 21 from the data reading section 19, this monitor can be easily monitored. The pressure signal comparison unit 20 compares the reference pressure signal Vx extracted from the data reading unit 19 in the diagnostic mode with the actual pressure signal V, and when it determines that there is an abnormality, the result is sent to the alarm display means 21. It is what is output.

The alarm allowable amount setting unit 23 includes a pressure signal comparing unit 19
The alarm permissible amount ε that is added when the above comparison is performed is set. As the allowable amount ε, for example, a measurement error allowed by each mass flow controller, or a fixed amount that is usually determined for the full-scale flow rate is often used, but it is not limited to this and is set variably according to the range of the control flow rate. It is also possible (2h in Fig. 2). The allowable amount storage unit 24 is a place for storing the set allowable amount ε.
(2i in FIG. 2). All the above functions are configured and processed in the microcomputer. The alarm display means 21 may be a buzzer or the like, or may be a visually appealing one such as a lamp,
Of course, there is no problem even if it serves as both.

Next, the console section C will be described. In addition to the normal power source, there are a key 30a for setting a diagnostic flow rate value, an alarm allowable amount setting key 30i, etc. in the console section C, and a key for storing and commanding a pressure signal, and a display of a mass flow rate setting signal , Functions such as alarm display are summarized. In addition, the console unit can be combined so that the same type of diagnosis can be performed for a plurality of mass flow controllers.

Next, the operation for diagnosing the presence or absence of abnormality will be described with reference to FIG. FIG. 6 shows an outline of a flow chart in the case of diagnosis. First, the normal changeover switch 14
Is located in the operation mode on the contact a side, and in this case, when the mass flow controller unit A functions to obtain a desired flow rate, for example, 65%, based on the mass flow rate setting signal g corresponding to this flow rate. Flow rate control is performed as described above. Next, when it is desired to diagnose the presence or absence of an abnormality in the subsequent use, the changeover switch 14 is switched to the diagnosis mode on the contact b side, and thereafter, the diagnostic flow rate value S% is set by the key 30a of the console C.
To set. (6a in FIG. 6) Since one feature of the present invention is that this setting can be freely performed, for example, 75% is set here. This may be a flow rate value that is not stored in advance, or a value below the decimal point can be set freely.
Next, by the setting signal automatic generation circuit 15, this flow rate value of 75%
The flow rate setting signal k75 corresponding to is calculated (6b in FIG. 6).
Next, the pressure signal V75 corresponding to the flow rate setting signal k75 is obtained (6c in FIG. 6), and this is read and output to the pressure signal comparison unit 20. If the flow rate setting signal k75 is previously stored at the time of the above-described initialization, the reference pressure signal V75 corresponding to the flow rate setting signal k75 is directly read from the reference data storage section 18 and output to the pressure signal comparing section 20. May be. At this time, the flow rate setting signal k75 is also input to the comparison unit 11.

On the other hand, the actual mass flow rate signal f65 detected by the sensor unit 3 is compared with the flow rate setting signal k75 described above, and the flow rate control valve 5 is controlled. At this time, the actual pressure signal V is detected by the pressure sensor. 'Is measured (6d in FIG. 6). Then, this pressure signal is obtained (6e in FIG. 6), and further the corresponding pressure signal V75 ′ is obtained (6f in FIG. 6), which is used as the pressure signal comparison unit 20.
The reference pressure signal V75 is compared with the pressure signal V75 '. When making this comparison, it may be determined that V75 is normal when V75 = V75 ′ and abnormal when V75 ≠ V75 ′, but it is desirable to add the allowable amount as described above. The allowable amount range ± ε input from the storage unit is taken in to determine V75−ε ≦ V75 ′ ≦ V75 + ε (6g in FIG. 6). Therefore, when the value is out of this range, the abnormal signal P is output to the alarm display means 21 to display the alarm. In addition, even when the value is out of the range, the timer is set (6i in FIG. 6) and the alarm is displayed for the first time when the same state continues for several seconds, for example, 5 seconds (6j in FIG. 6).
(6k in FIG. 6), a warning display may be displayed until then. Further, if the result of the above comparison is within the range, a normal signal O may be output for OK display. As described above, it is possible to self-diagnose whether or not there is an abnormality in the sensor unit.

In the above embodiment, the comparison judgment is performed using the reference pressure signal V which has not been linearly corrected, but in another embodiment, the corrected pressure signal after the linear correction is performed. v and the pressure signal actually output were corrected linearly
It is also possible to make a comparison and judgment in the same manner as above using v ′. In still another embodiment, the actual pressure signal is not used as a comparison target as described above, but the actual pressure signal is replaced with the data of the reference pressure signal V or v stored in advance to obtain a reference. It is also possible to obtain a corresponding value in the characteristic data and compare this with a reference pressure signal based on the flow rate setting signal to make a determination. It is also possible to prepare reference characteristic data for a plurality of chamber pressures, switch to the corresponding chamber pressure data when the actual chamber pressure changes, and then perform the same comparison and determination. The change-over switches 14a and 14b may be of an automatic change-over type so that they are automatically changed over from a to b when a diagnostic flow rate value is inputted.

[0021]

As described above, according to the mass flow controller with an abnormality diagnosing function of the present invention, since the flow rate value to be diagnosed can be set arbitrarily and at any time, it is possible to confirm whether or not there is an abnormality in the sensor unit such as clogging. Has spread and can be flexibly dealt with, making it easier to use. In particular, it is suitable for a mass flow controller used in a semiconductor manufacturing process in which the control flow rate and the inlet pressure of the mass flow controller are changed relatively frequently.

[Brief description of drawings]

FIG. 1 is a block diagram of a mass flow controller with an abnormality diagnosis function of the present invention.

FIG. 2 is a flowchart for setting reference characteristic data in an initial state.

FIG. 3 is a diagram showing a relationship between a flow rate value and a pressure signal.

FIG. 4 is a diagram showing a relationship between reference characteristic data including a flow rate setting signal and a pressure signal.

FIG. 5 is a diagram in which the reference characteristic data is linearized.

FIG. 6 is a flowchart for diagnosing an abnormality in a usage state.

FIG. 7 is a block diagram showing a conventional mass flow controller.

[Explanation of symbols]

 2 ... Bypass section 3 ... Sensor section 5 ... Flow control valve 11 ... Comparison section 12 ... Valve drive voltage determination circuit 14 ... Changeover switch 15 ... Setting signal automatic generation circuit 16 ... Reference pressure signal storage section 17 ... Reference pressure signal linearization circuit 18 ... Reference data storage unit 19 ... Data reading unit 20 ... Pressure signal comparison unit 21 ... Alarm display means 26 ... Pressure sensor

Claims (4)

[Claims] 1. An inflow path for a fluid, a bypass flow path through which the fluid flows from the inflow path, a sensor flow path branched from the bypass flow path and in which a fluid having a predetermined diversion ratio flows, and the sensor flow path. A flow rate sensor for measuring the flow rate of the fluid, an outflow path through which the fluids in the bypass flow path and the sensor flow path merge, a flow rate control valve provided in this outflow path, and a mass flow rate signal detected by the flow rate sensor. In a mass flow controller having a comparison control unit that compares a preset mass flow rate setting signal and outputs a valve drive signal to the flow rate control valve, pressure detection means is provided downstream of the flow rate control valve, and the total flow rate is set in advance. Means to measure the pressure signal corresponding to the flow rate setting signal step by step over the setting range, to store these as the reference pressure signal, means to input the flow rate setting value in the operating state, and this flow rate setting A means for reading out the reference pressure signal corresponding to the value, a comparing means for comparing the read reference pressure signal with the pressure signal actually output from the pressure detecting means at this time by considering the allowable amount, and this comparison. A mass flow controller with an abnormality diagnosing function, comprising: a display unit for displaying an abnormality signal according to a result. 2. A correction means for linearizing the reference characteristic data consisting of the flow rate setting signal and the reference pressure signal and the actually detected pressure signal is provided, and the corrected reference pressure signal and the corrected pressure signal are allowed. The mass flow controller with an abnormality diagnosing function according to claim 1, wherein the mass flow controller compares the capacities with each other. 3. A fluid inflow passage, a bypass flow passage through which the fluid from the inflow passage flows, a sensor flow passage branched from the bypass flow passage and in which a fluid having a predetermined diversion ratio flows, and the sensor flow passage. A flow rate sensor for measuring the flow rate of the fluid, an outflow path through which the fluids in the bypass flow path and the sensor flow path merge, a flow rate control valve provided in this outflow path, and a mass flow rate signal detected by the flow rate sensor. In a mass flow controller having a comparison control unit that compares a preset mass flow rate setting signal and outputs a valve drive signal to the flow rate control valve, a pressure signal corresponding to the flow rate setting signal is preset in stages over the entire flow rate setting range. And use these as reference pressure signals, input the flow rate set value in the operating state, and use the reference pressure signal corresponding to this flow rate set value and the actual value downstream of the flow control valve at this time. And a pressure signal detected compared in consideration of the allowable amount, the abnormality diagnostic method of a mass flow controller and displaying an error signal in accordance with the comparison result. 4. The reference characteristic data including the flow rate setting signal and the reference pressure signal and the actually detected pressure signal are linearly corrected, and the corrected reference pressure signal and the corrected pressure signal are adjusted to an allowable amount. 4. The comparison is performed by taking into consideration.
Abnormality diagnosis method for the described mass flow controller.