JP2004246826A - Mass flow controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mass flow controller which is simple in configuration and nevertheless can perform flow control while confirming whether the flow rate is appropriately controlled. <P>SOLUTION: The mass flow controller comprises an opening control valve 4 which controls the flow of fluid passing in a channel 2; a pressure sensor 7b disposed on the downstream side of the control valve 4; a throttling part 6 disposed on the downstream side of the pressure sensor 7b; a flow sensor 5 which measures the flow rate F of the fluid passing in the channel 2; and a control unit 8 which uses the outputs Spb, Sf of the pressure sensor 7b and the flow sensor 5 to control the opening/closing of the control valve 4, thereby controlling the flow rate F of the fluid passing through the throttling part 6, and monitors the flow rate F. <P>COPYRIGHT: (C)2004,JPO&amp;NCIPI

Description

[0001]
[0001] The present invention relates to a mass flow controller. More specifically, the present invention relates to a mass flow controller using a throttle unit.
[0002]
[Prior art]
FIG. 3 is a diagram showing an example of a semiconductor manufacturing line 10 using a conventional mass flow controller. In FIG. 3, reference numeral 11 denotes a chamber constituting a semiconductor manufacturing line, 12 denotes a gas supply line for supplying different gases Ga and Gb to the chamber 11, and 13 and 14 denote gas cylinders for supplying the respective gases Ga and Gb.
[0003]
The gas supply line 12 includes a mechanical pressure regulator 15, a gauge 16 on the downstream side of the pressure regulator 15, and a filter 17. Reference numeral 18 denotes a mass flow controller, and reference numerals 19a and 19b denote on-off valves provided upstream and downstream of the mass flow controller 18, respectively. Reference numeral 20 denotes a mass flow meter that measures the flow rates of the gases Ga and Gb flowing through the gas supply line 12.
[0004]
That is, the gas supply line 12 selectively supplies one of the two gases Ga and Gb to the chamber 11 as appropriate, and allows the flow rate thereof to be adjusted by the mass flow controller 18. Further, as the gases Ga and Gb used in the semiconductor manufacturing process, for example, a process gas Ga and an inert gas Gb for confirming a flow rate can be considered.
[0005]
The mass flow controller 18 includes a pressure sensor 18a and a throttle 18b such as a sonic venturi, and controls the flow rate appropriately by adjusting the pressure on the upstream side of the throttle 18b.
[0006]
[Problems to be solved by the invention]
However, the flow path of the narrowed portion 18b may be narrowed due to a change with time, and even if the pressure is kept constant, it may not be possible to flow the gas Ga at a flow rate corresponding thereto.
[0007]
Therefore, as in the example shown in FIG. 3, by monitoring the flow rate of the inert gas Gb adjusted by the mass flow controller 18 with the inert gas Gb flowing, the flow rate control of the mass flow controller 18 is performed properly. To see if it has been done. However, in the gas supply line 12 as shown in FIG. 3, it is necessary to provide a separate mass flow meter 20 only for checking the state of the mass flow controller 18, so that the gas supply line 12 is complicated and the cost is high. .
[0008]
In addition, the more complicated the gas supply line 12 is, the more complicated the control becomes. In addition, it is inevitable that the rate of occurrence of gas leakage and failure increases.
[0009]
In addition, the primary side of the mass flow controller 18 and the mass flow meter 20 as described above is provided with the pressure regulator 15 for pressure adjustment and pressure fluctuation countermeasures. The supply panel could not be reduced.
[0010]
SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described matters, and has a simple configuration, and is capable of performing a flow control while confirming whether or not a flow control is properly performed. To provide a controller.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a mass flow controller according to a first aspect of the present invention includes an opening / closing control valve for controlling a flow of a fluid flowing in a flow path, a pressure sensor disposed downstream of the opening / closing control valve, A throttle disposed on the downstream side, a flow sensor for measuring the flow rate of the fluid flowing through the flow path, and using the outputs of the pressure sensor and the flow sensor to control the opening / closing control valve to flow through the throttle. It is characterized in that a control unit for controlling the flow rate of the fluid and for monitoring the flow rate is provided. (Claim 1)
[0012]
Therefore, the flow rate of the fluid measurable by the flow sensor and the pressure of the fluid upstream of the throttle portion measurable by the pressure sensor are respectively measured, and one of the states of the fluid measured by two different methods is opened and closed. It can be used for feedback control of the valve, and the other can be used as a flow rate monitor of the fluid flowing to the mass flow controller.
[0013]
That is, for example, the control unit controls the opening and closing of the on-off control valve using the output of the pressure sensor to adjust the pressure on the upstream side of the throttle unit, thereby adjusting the flow rate of the fluid passing through the throttle unit. In the case of monitoring using the output of the sensor, the mass flow controller can monitor the operation using the output of the flow sensor while controlling the flow by the pressure of the fluid on the upstream side of the throttle unit. Thus, when an abnormality such as clogging occurs in the throttle unit, the abnormality can be quickly found, and more reliable flow control can be performed. Further, it is not necessary to separately provide a member such as a mass flow meter for confirming the operation of the mass flow controller as in the related art, and the configuration of the gas supply line can be simplified accordingly.
[0014]
In the case where the flow sensor is provided on the upstream side of the pressure sensor (claim 2), since the throttle portion can be located in the flow path immediately below the pressure sensor, the pressure drop caused by the flow sensor is reduced. Irrespective of this, the pressure immediately above the throttle unit can be accurately adjusted using the output of the pressure sensor, and the accuracy of flow control can be improved accordingly.
[0015]
In the case where the flow rate sensor is provided on the upstream side of the on-off control valve (Claim 3), even if the evacuation is performed to such an extent that the inside of the flow path on the downstream side of the mass flow controller is substantially in a vacuum state, Since the open / close control valve is located between the secondary flow path of the controller and the flow sensor, the inside of the flow sensor is not evacuated, and the flow sensor does not malfunction, thereby improving reliability.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a block diagram showing an example of the mass flow controller 1 of the present invention. The mass flow controller 1 of the present embodiment includes a flow path block 3 forming a flow path 2 for flowing a fluid (a gas is exemplified as a fluid in the following example, but the fluid is not limited to a gas). An opening / closing control valve 4 connected to the flow path block 3, a flow sensor 5, a throttle section 6, two pressure sensors 7, a control section 8 for controlling the opening / closing control valve 4, and a filter 9. are doing.
[0017]
The flow path 2 is formed, for example, so as to hollow out the inside of the flow path block 3, and has a first flow path 2a and a second flow path 2b. Further, pipe attachment portions 3a and 3b are provided at the upstream end and the downstream end of the flow path 2, respectively. The flow path 2 may be formed by excavation, by using a mold, or by another method. When the second flow path 2b is formed by excavation or the like, a flow path block is formed. 3 needs to be formed in at least one place so as to be separable, but in any case, gas leakage can be prevented by integrally molding the flow path blocks 3, 3a, 3b.
[0018]
The opening / closing control valve 4 includes, for example, a diaphragm 4a abutting on a valve seat 3c formed on one side surface of the flow path block 3 and an actuator 4b thereof, and the flow paths 2a, 2b are controlled by an opening control signal (pressure control signal) Cp. Is configured to be controllable.
[0019]
The flow sensor 5 includes, for example, a rectifier 5a inserted into the second flow path 2b, a branch flow path 5b that branches from the second flow path 2b by a flow rate of a predetermined ratio 1 / A, and a flow path 5b. And a flow path signal Sf indicating the total flow rate F.
[0020]
The throttle unit 6 is, for example, a sonic nozzle that flows a fluid having a flow rate corresponding to the pressure on the primary side when the pressure difference between the primary side and the secondary side is equal to or greater than a predetermined value. The block in which the throttle portion 6a is formed is arranged so as to communicate with the flow path 2b at the downstream end side of the flow path 2b. In the present invention, the configuration of the throttle section 6 is not limited to the sonic nozzle, but may be any as long as the throttle section 6a for forming a resistance in the flow path 2 is formed.
[0021]
The opening / closing control valve 4 and the flow sensor 5 are arranged side by side on one side surface (upper surface) of the flow path block 3, so that the overall size of the mass flow controller 1 can be reduced.
[0022]
The pressure sensor 7 includes a first sensor 7a disposed on a side surface facing the first flow path 2a and a second sensor 7b disposed on a side surface facing the second flow path 2b. The pressure sensors 7a and 7b are provided on a surface different from the side surface on which the components 4 to 5 are attached (in this example, a first surface located in front of the first flow path 2a and a position located immediately before the rectifier 5a constituting the flow sensor 5 in FIG. 1). (Back of two flow paths). Thereby, the pressure sensor 7 can be installed without changing the overall size of the mass flow controller 1. The sensors 7a and 7b output pressure signals Spa and Spb indicating the pressures Pa and Pb in the first flow path 2a and the second flow path 2b, respectively.
[0023]
In this example, the sensors 7a and 7b are provided on the side surfaces. However, the mounting surface of the pressure sensor 7 is not limited as long as the pressure sensor 7 can be mounted so as to face the flow path 2. In other words, it goes without saying that the control valve 4 and the flow rate sensor 5 may be embedded in the lower surface of the flow path block 3 or at a position where they do not interfere with the flow sensor 5.
[0024]
The control unit 8 outputs the opening control signal Cp by feeding back the pressure signals Spa and Spb (output) from the pressure sensor 7 and the flow control signal Sf (output) from the flow sensor 5 to thereby open and close the control valve. 4 has a processing unit 8a for performing feedback control of the control unit 4 and an external interface 8b.
[0025]
Although not shown, the mass flow controller 1 of this example has a display unit for displaying values F, Pa, and Pb measured by the sensors 5, 7a, and 7b. Further, the values F, Pa, Pb measured by the sensors 5, 7a, 7b can be output to the outside via the interface 8b. In this example, an example is shown in which the interface 8b inputs and outputs analog values. However, the interface 8b may communicate digitally.
[0026]
In addition, the open / close control of the open / close control valve 4 is not limited to the feedback control using only the output signal Spb of the pressure sensor 7b, and may be controlled using the output signal Spa of the pressure sensor 7a. By providing the pressure sensor 7a as shown in this example, it is possible to monitor the pressure of the gas input to the mass flow controller 1, but it is also possible to omit the pressure sensor 7a. Not even.
[0027]
Further, since the mass flow controller 1 of the present embodiment has the built-in filter 9, there is no need to connect and connect a separate filter 16 unlike the conventional case. That is, the gas supply line can be simplified accordingly, and the installation area can be reduced. In this example, an example is shown in which the filter 9 is provided at the most upstream end of the flow path 2 to prevent a malfunction due to entry of foreign matter, but the present invention does not limit the position of the filter 9. In some cases, the filter 9 can be omitted.
[0028]
In the mass flow controller 1 having the above configuration, the processing unit 8a inputs the flow rate setting signal Fs via the interface 8b, and adjusts the flow rate F of the fluid flowing through the mass flow controller 1 to match the flow rate setting signal Fs. Further, in the mass flow controller 1 of the present embodiment, the processing unit 8 feeds back the open / close control valve 4 using the output (pressure signal Spb) of the pressure sensor 7b to control the open / close of the valve 4, thereby controlling the flow rate of the fluid flowing through the sonic nozzle 6. In addition to controlling the flow rate F, the flow rate F actually flowing using the output (flow rate signal Sf) of the flow rate sensor 5 at this time is measured to confirm the operation.
[0029]
In the case of this example, since the output Spb of the pressure sensor 7b is used for opening / closing control of the opening / closing control valve 4, a high-speed response of the flow rate control can be achieved, but the present invention is not limited to this point. is not. That is, the processing unit 8 controls the opening / closing of the opening / closing control valve 4 using the output Sf of the flow rate sensor 5 and, at the same time, determines the flow rate F of the fluid actually flowing through the sonic nozzle 6 by another method using the output Spb of the pressure sensor 7b. It is also possible to confirm with.
[0030]
In any case, the control unit 8 makes the set flow rate Fs surely flow by making the measurement principle of the flow rate of the sensor 5b or 5 used for flow rate control different from that of the sensor 5 or 7b used for flow rate control. Can be confirmed more reliably. In other words, the reliability of the mass flow controller 1 can be improved, and there is no need to separately attach a mass flow meter 20 for checking the flow rate F of the fluid flowing through the mass flow controller 1 as in the related art, thereby achieving simplification of the gas supply line. it can.
[0031]
Further, in the case of this example, since the flow sensor 5 is disposed on the upstream side of the pressure sensor 7b, the pressure sensor 7b can be disposed in the flow path immediately above the throttle section 6, so that the flow of the fluid flowing through the flow sensor 5 The pressure drop caused by the pressure sensor 7b does not adversely affect the control of the pressure Pb just above the throttle unit 6 measured by the pressure sensor 7b, and thus, the control can be performed with higher accuracy.
[0032]
However, the present invention is not limited to the configuration in which the flow sensor 5 is disposed on the upstream side of the pressure sensor 7b, and this pressure sensor may be provided on the upstream side of the flow sensor 5. In this case, since the pressure of the fluid flowing into the flow sensor 5 can be kept constant, the flow sensor 5 can perform more accurate flow measurement. Needless to say, the pressure sensor 7 may be provided on both the upstream side and the downstream side of the flow sensor 5. In this case, in addition to the flow rate measurement in addition to the flow rate sensor 5 and the pressure sensor 7b, it is also possible to measure the flow rate by a pressure difference immediately above and immediately below the flow rate sensor 5, and by using this, a more reliable mass flow meter 1 is formed. can do.
[0033]
Further, as shown in this example, the opening / closing control valve 4 and the flow rate sensor 5 are arranged side by side, and the second flow path 2b located therebetween is made as short as possible. The time delay of the pressure Pb with respect to the output can be made as small as possible, and the fluctuation of the pressure Pb can be made as small as possible.
[0034]
Further, by arranging the pressure sensor 7b at a position as close to the flow sensor 5 as possible in the second flow path 2b between the opening / closing control valve 4 and the flow sensor 5 (flow path immediately preceding the flow sensor 5), the influence of turbulence and the like is obtained. Pressure Pb can be measured. That is, the control accuracy and stability of the flow rate by the mass flow controller 1 can be improved accordingly.
[0035]
In addition, by eliminating a joint or a pipe from the inside of the second flow path 2b between the opening / closing control valve 4 and the flow rate sensor 5, it is possible to eliminate the risk of pressure drop and gas leakage due to resistance of the flow path.
[0036]
FIG. 2 is a block diagram showing a modification of the mass flow controller 1. In FIG. 2, portions denoted by the same reference numerals as those in FIG. 1 are the same or equivalent portions, and thus detailed description thereof will be omitted. The example shown in this example differs from the example shown in FIG. 1 in that a flow rate sensor 5 is provided in the flow path 2 a on the upstream side of the on-off control valve 4.
[0037]
With the configuration as in the present example, even if the pressure on the secondary side of the mass flow controller 1 is reduced to a substantially vacuum state by a vacuum pump or the like, the inside of the flow sensor 5 disposed upstream of the on-off control valve 4 is not affected. Since there is no evacuation and fluid is present in the flow path sensor 5, the flow path sensor 5 does not malfunction. That is, the flow rate control can be performed without being affected by the decrease in the secondary pressure during the small flow rate control, and the reliability of the flow rate control can be improved accordingly.
[0038]
In the case of this example, the pressure Pa of the fluid supplied to the mass flow controller 1 can be obtained by disposing the pressure sensor 7a on the primary side of the flow sensor 5. That is, the control section 8 corrects the output (flow signal Sf) of the flow sensor 5 using the output (pressure signal Spa) of the pressure sensor 7a, thereby making it possible to reduce the influence of the fluctuation of the primary pressure. Thus, the flow rate control with higher accuracy can be performed.
[0039]
As described above, the present invention monitors the flow rate while controlling the flow rate using physical quantities measured by two different sensors, even though the mass flow controller has a simple configuration. Extremely reliable flow control can be performed.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a mass flow controller of the present invention.
FIG. 2 is a diagram showing a modification of the mass flow controller.
FIG. 3 is a diagram showing an example of a semiconductor manufacturing line using a conventional mass flow controller.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Mass flow controller, 2 ... Flow path, 4 ... Opening / closing control valve (pressure control valve), 5 ... Flow rate sensor, 6 ... Throttle part, 7b ... Pressure sensor, 8 ... Control part.

Claims (3)

An on-off control valve for controlling the flow of a fluid flowing in the flow path;
A pressure sensor arranged downstream of the on-off control valve,
A restrictor disposed downstream of the pressure sensor;
A flow sensor for measuring the flow rate of the fluid flowing through the flow path,
The output of the pressure sensor and the flow rate sensor is used to control the flow rate of the fluid flowing through the throttle section by controlling the opening / closing control valve to open and close, and a control section for monitoring the flow rate is provided. Mass flow controller. The mass flow controller according to claim 1, wherein the flow sensor is provided on an upstream side of the pressure sensor. 3. The mass flow controller according to claim 1, wherein the flow rate sensor is provided on an upstream side of the on-off control valve.

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