JP2021056737A - Mass flow controller, fluid control device, and semiconductor manufacturing apparatus - Google Patents

Abstract

To provide a mass flow controller (MFC) that includes a determination mechanism for aging completion and can increase the operation rate by shortening the aging time.SOLUTION: A mass flow controller includes an aging management unit 33 that manages whether a mass flow controller is activated and the state of a heat generation resistor and a flow rate sensor unit, which changes by electrification to each part of the mass flow controller, becomes a flow rate measurement possible state. The aging management unit 33 controls the heat generation quantity from heat generation resistors 23a and 23b just after the activation of the mass flow controller to be larger than the general heat generation quantity for the flow rate measurement, and when a predetermined condition is satisfied, switches the heat generation quantity to the general heat generation quantity for the flow rate measurement.SELECTED DRAWING: Figure 2

Description

The present invention relates to a mass flow controller, a fluid control device, and a semiconductor manufacturing device.

Conventionally, a mass flow controller (MFC) has been used as a mass flow rate control device for process gas or the like used in a semiconductor manufacturing process, and a thermal MFC is often used for particularly precise flow rate measurement.
This thermal MFC is a device that feedback-controls the regulating valve based on the flow rate measured by the thermal flow sensor and sends the fluid (gas, etc.) supplied from the primary side to the secondary side by the specified flow rate. Is.

The thermal flow sensor has a sensor flow path through which a part of the fluid passing through the MFC flows for flow measurement, and both heat is generated while energizing and heating with heat generating resistors provided on the upstream side and the downstream side in the middle. The mass flow rate of the fluid flowing through the sensor flow path is measured from the temperature difference detected as the resistance value difference of the resistor.
The sensor flow path is connected in parallel with the bypass flow path through which most of the other fluids flow, and the flow rate ratio between the sensor flow path and the bypass flow path is known and is almost constant regardless of the pressure. From the flow rate, the mass flow rate of the fluid flowing through the MFC can be calculated (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-162064

Immediately after the MFC is started, it is necessary to energize each part of the MFC and perform aging (warm-up) to stand by. The reason is that the thermal flow sensor and the PCB of the control unit generate heat when energized at startup, so the temperature of the entire MFC rises, but the zero point of the MFC is not stable during the temperature rise and is accurate. This is because the mass flow rate cannot be controlled.

Conventionally, in some MFCs equipped with a temperature sensor, there is no mechanism for determining the completion of aging, and aging is completed by waiting for several tens of minutes after activation.
Further, since this aging needs to be performed every time the MFC is started, there is a problem that the MFC cannot be used during that time.

An object of the present invention is to provide a mass flow controller (MFC) capable of solving such a problem, providing a mechanism for determining the completion of aging, and shortening the aging time to increase the operating rate.

The mass flow controller of the present invention has a thermal flow rate sensor unit having a built-in heat generating resistor for measuring the mass flow rate of the fluid passing through the fluid flow path through which the fluid passes, and the measurement was performed by the flow rate sensor unit. A mass flow controller that controls the opening degree of the adjusting valve so that the mass flow rate of the fluid becomes a predetermined value and adjusts the flow rate of the fluid passing through the fluid flow path.
It has an aging management unit that manages whether or not the thermal state of the flow rate sensor unit, which changes when the mass flow controller is activated and energizes the heat generating resistor and each part of the mass flow controller, becomes a flow rate measurable state.
Immediately after the mass flow controller is started, the aging control unit controls the calorific value of the heat generating resistor to a calorific value larger than the normal calorific value for flow rate measurement, and when a predetermined condition is satisfied, the heat generation control unit is used for the flow rate measurement. Switch to the normal calorific value of.

Preferably, it further has a resistance value detecting circuit for detecting the resistance value of the heat generating resistor.
When the resistance value detected by the resistance value detection circuit reaches a predetermined value, the aging management unit switches the heat generation amount of the heat generation resistor to the normal heat generation amount for the flow rate measurement.

More preferably, the aging control unit switches the heat generation amount of the heat generation resistor to the normal heat generation amount for measuring the flow rate, and then determines that the resistance value is within a predetermined range, and then determines that the resistance value is within a predetermined range. It is judged that the thermal state of is in the state where the flow rate can be measured.

The fluid control device of the present invention is a fluid control device in which a plurality of fluid devices are arranged.
The plurality of fluid devices are fluid control devices including the above-mentioned mass flow controller.

The semiconductor manufacturing apparatus of the present invention uses the above-mentioned mass flow controller to control the process gas in a semiconductor manufacturing process that requires a processing step with a process gas in a closed chamber.

According to the present invention, the resistance heating element built in the flow sensor is used to increase the amount of heat generated from the resistance heating element for a predetermined time immediately after the start of the mass flow controller, so that the aging (warm-up) time is shortened. It is possible to provide a mass flow controller with an improved operating rate.

The vertical sectional view which conceptually shows the MFC which concerns on embodiment of this invention. The explanatory view which shows an example of the bridge circuit, the resistance value detection circuit, and the aging circuit part of a flow rate sensor. The flowchart which shows an example of the aging management process. Explanatory drawing which shows an example of resistance value change at the time of aging management. The schematic perspective view which shows the fluid control apparatus which concerns on embodiment of this invention. The block diagram which shows the semiconductor manufacturing apparatus which concerns on embodiment of this invention.

Hereinafter, the MFC according to the embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a vertical cross-sectional view conceptually showing the MFC of the present embodiment.

The MFC 1 mainly includes a body 10, a flow rate sensor unit 20, a control unit 30, and a flow rate adjusting valve 40.

The body 10 is made of a steel material such as stainless steel, has a rectangular parallelepiped outer shape, and has joints attached to both end faces thereof. The body 10 is formed with an inflow path 11a, a sensor inflow path 13a, a bypass flow path 12, a sensor outflow path 13b, a valve chamber 14, and an outflow path 11b.

The fluid that has passed through the inflow path 11a flows into the bypass flow path 12. The sensor inflow path 13a branches from the upstream of the bypass flow path 12 and allows fluid to flow to the flow rate sensor unit 20. The sensor outflow path 13b allows the fluid that has passed through the flow rate sensor unit 20 to flow out and joins downstream of the bypass flow path 12.

The bypass flow path 12 and the sensor inflow path 13a are configured to allow fluid to flow at a predetermined flow rate ratio (for example, 1: 2 to 1: 1000). A plurality of bypass sheets are provided in the bypass flow path 12. The valve body of the flow rate adjusting valve 40 is arranged in the valve chamber 14.

The flow rate sensor unit 20 is a thermal type flow rate sensor unit, and is composed of a sensor base main body 21, a sensor flow path 22 composed of a thin tube, and heat generating coils wound on the upstream side and the downstream side in the middle of the sensor flow path 22. A pair of heat generating resistors 23a and 23b and a bridge circuit 28 which is an output unit are mainly provided.

As shown in FIG. 2, the bridge circuit 28 is a circuit in which the heating resistors 23a and 23b and the reference resistors R1 and R2 are connected in this order in a diamond shape, and an input voltage is applied between the connection points P1 and P2 to connect them. The output voltage is obtained from between points P3 and P4. Although the bridge circuit 28 is physically provided on the board of the control unit 30, it is functionally considered to be the output unit of the flow rate sensor unit 20. Therefore, in the present specification, the flow rate sensor unit 20 is used. Treat as a component. Further, the aging management unit 33 is provided on the board of the control unit 30.
As a power source for applying an input voltage to the connection point P1 of the bridge circuit 28, a power supply voltage Vn for normal flow rate measurement (normal heat generation amount for flow rate measurement) and heating at startup of MFC1 (normal heat generation amount for flow rate measurement). There is a power supply voltage Ve (with a larger calorific value), and the connection state between these power supply voltages Vn, Ve and the bridge circuit 28 is switched by the switch SW. The connection state of the switch SW is switched by the switching signal SG1 from the aging management unit 33.
In this embodiment, the resistance value detection circuit 25 is provided upstream of the connection point P1. These functions will be described later.

The control unit 30 calculates the flow rate of the fluid based on the signal from the flow rate sensor unit 20, and performs feedback control to output a control signal to the flow rate adjusting valve 40 so that the fluid flowing through the bypass flow path 12 has a predetermined flow rate. Do. The control unit 30 includes an amplifier 31, an AD converter (not shown), a comparison control unit 32, a DA converter (not shown), an amplifier (not shown), and an aging management unit 33. The comparison control unit 32 is a program executed by the microcomputer CPU, not a physical unit.

The flow rate adjusting valve 40 is a valve that opens and closes a fluid flow path based on a control signal from the control unit 30, and includes a valve body and a drive actuator.

In the present embodiment, a resistance value detection circuit 25 for measuring the resistance values Ra and Rb of the heat generating resistors 23a and 23b of the flow rate sensor unit 20 is provided.
Specifically, as shown in FIG. 2, a resistance value detection circuit 25 is provided upstream of the connection point P1 of the bridge circuit 28 to detect the current flowing through the entire bridge circuit 28. The resistance value detection circuit 25 may be, for example, a type that measures the voltage applied to the shunt resistance inserted in the circuit to be measured.
When the voltage of the constant voltage power supply (not shown) that supplies voltage to the bridge circuit 28 is V0 and the current detected by the resistance value detection circuit 25 is I, assuming that the voltage drop of the resistance value detection circuit 25 can be ignored, the entire bridge circuit The resistance value R (between the connection points P1 and P2) is given by the following equation.

Since the current passing between the connection points P3 to P4, which is the output terminal of the bridge circuit 28, is considered to be negligible, the resistance value R of the entire bridge circuit is such that the heating resistors 23a, 23b (resistance values Ra, Rb) are connected in series. It is the resistance value when the resistance connected to and the resistance connected in series with the reference resistors R1 and R2 are connected in parallel, and it is considered that the following relationship is established.

Therefore, the total of the resistance values Ra and Rb of the heat generating resistors 23a and 23b can be obtained from the calculated resistance value R and the known resistances R1 and R2 by the following formula.

The change in the total value Ra + Rb is used as an index of the completion of aging.
When the reference resistors R1 and R2 are sufficiently larger than the resistance values Ra and Rb, Ra + Rb is substantially equal to R from the above equation (3). Therefore, the change in the resistance value R of the entire bridge circuit is used as an index of aging completion. May be used as.
The resistance value detection circuit 25 is not limited to the above, and various known circuits capable of measuring the resistance values Ra and Rb of the heat generating resistors 23a and 23b may be used.

Next, the operation of the MFC 1 of the present embodiment configured in this way will be described with reference to FIGS. 3 and 4.
When the MFC1 is activated and the power is turned on (step S1), the aging management unit 33 selects the heating mode (step S2) and outputs a switching signal SG1 for connecting the power supply voltage Ve to the bridge circuit 28 to the switch SW. To do. The power supply voltage Ve is larger than the power supply voltage Vn for normal flow rate measurement because the amount of heat generated by the heat generating resistors 23a and 23b is increased from the time of normal flow rate measurement. The size is not particularly limited, but is determined in consideration of the magnitudes of the voltage and current that can be supplied from the printed circuit board, the temperature range in which the resin coatings of the heat generating resistors 23a and 23b cannot be melted, and the like.

When the power supply voltage Ve is supplied, the heat generating resistors 23a and 23b generate heat and heat the flow rate sensor unit 20. As a result, the resistance value detected by the resistance value detection circuit 25 also increases as shown in Graph B of FIG.
The aging management unit 33 compares the resistance value detected by the resistance value detection circuit 25 with the predetermined resistance threshold value Rt (step S3). This resistance threshold value Rt is set to a value lower than the resistance value Rs when the thermal equilibrium state is reached, in order to prevent the temperature from becoming too high due to the occurrence of overshoot. The process of step S3 is repeated until the resistance value detected by the resistance value detection circuit 25 exceeds the resistance threshold value Rt.
When the resistance value detected by the resistance value detection circuit 25 exceeds the resistance threshold value Rt, the aging management unit 33 selects the normal mode (step S4) and connects the power supply voltage Vn to the bridge circuit 28. The switching signal SG1 is output to the switch SW. As a result, as shown in FIG. 4, the rate of increase in the resistance value detected by the resistance value detection circuit 25 decreases, but the resistance value Rs in the thermal equilibrium state is approached.
The aging management unit 33 determines whether the change in the resistance value detected by the resistance value detection circuit 25 is within a predetermined range, that is, is constant (step S5). Immediately after switching from the power supply voltage Ve to the power supply voltage Vn, the thermal equilibrium state is not reached, and it is necessary to monitor the change in the resistance value detected by the resistance value detection circuit 25. If the change in the resistance value detected by the resistance value detection circuit 25 is large, the process of step S5 is repeated.

When the aging management unit 33 determines that the change in the resistance value detected by the resistance value detection circuit 25 is within a predetermined range (at the time of EP1), the aging management unit 33 outputs a completion signal SG2 (see FIG. 2) of the aging process and controls it. Unit 30 determines that the flow rate can be measured, and ends the aging process (step S7).

As shown in Graph A in FIG. 4, when the heating mode as described above is not adopted, it is relative until the resistance value detected by the resistance value detection circuit 25 reaches the resistance value Rs in the thermal equilibrium state (at the time of EP0). You can see that it takes a long time.

When the aging is completed, the control unit 30 adjusts the zero point by reading and storing the output of the flow rate sensor unit 20 in a state where no fluid flows through the MFC.
The heat generating resistors 23a and 23b on the upstream side and the downstream side are energized to generate heat, and the resistance values Ra and Rb (proportional to the temperature) of these heat generating resistors 23a and 23b are detected. When a fluid flows in the sensor flow path 22, the heat generating resistor 23a on the upstream side is cooled by the flowing fluid to suppress the temperature rise, and the heat generating resistor 23b on the downstream side is a heat generating resistor on the upstream side. Since the fluid heated in 23a flows, the temperature rises significantly, and as a result, a temperature difference occurs between the two heating resistors 23a and 23b. This temperature difference can be regarded as proportional to the mass flow rate of the fluid in a certain flow rate range. The bridge circuit 28 converts the resistance value difference Ra-Rb of the heat generating resistors 23a and 23b, which is an index of the temperature difference, into _{an output voltage V out between the connection points P3 and P4 and outputs the voltage.}
(If the reference resistors R1 and R2 _{equal, V out = V in × (} Rb-Ra) / (Ra + Rb) _{becomes, V out} is approximately proportional to the Rb-Ra.)

The output side signal line from the bridge circuit 28 of the flow rate sensor unit 20 is input to the amplifier 31 composed of an operational amplifier as shown in FIGS. 3 and 1. The amplified output signal is digitized by an AD converter (not shown). The digitized signal is further processed to calculate the flow rate value. The calculated flow rate value is input to the comparison control unit 32.
The comparison control unit 32 compares the calculated flow rate value with the flow rate set value input from an external controller (not shown), and outputs a control signal. This control signal may be a simple difference signal between the calculated flow rate value and the flow rate set value, but is preferably a PID control signal based on the difference and its integral and derivative.
This control signal is converted into an analog voltage by a DA converter (not shown) and further amplified by an amplifier (not shown) composed of an operational amplifier to drive the flow rate adjusting valve 40.
By performing such feedback control, the mass flow rate of the fluid flowing through the MFC 1 is adjusted to a predetermined value.

In the present embodiment, the heat generation amount of the heat generation resistors 23a and 23b is increased in the heating mode when the MFC1 is started, and the heat generation amount is switched to the normal flow rate measurement in the normal mode on the way. It is easier to smoothly shift to the thermal equilibrium state as compared with the case of heating from.

In the present embodiment, switching from the heating mode to the normal mode is performed based on the resistance value detected by the resistance value detection circuit 25, but the present invention is not limited to this, and the heating mode is performed for a predetermined time. , It is also possible to switch to normal mode. It is also possible to monitor the temperature of the flow rate sensor unit 20 with a temperature sensor and switch to the normal mode when a predetermined temperature is reached.

Next, the fluid control device of the present invention will be described.
FIG. 5 is a schematic perspective view of the fluid control device according to the embodiment of the present invention.
The fluid control device shown in FIG. 5 is provided with a metal base plate BS arranged along the width directions W1 and W2 and extending in the longitudinal directions G1 and G2. W1 indicates the front side, W2 indicates the back side, G1 indicates the upstream side, and G2 indicates the downstream side. Various fluid devices 991A to 991E are installed in the base plate BS via a plurality of flow path blocks 992, and a flow (not shown) in which a fluid flows from the upstream side G1 to the downstream side G2 in the plurality of flow path blocks 992. Each road is formed.

Here, the "fluid device" is a device used for a fluid control device that controls the flow of a fluid, includes a body that defines a fluid flow path, and at least two flow paths that open on the surface of the body. It is a device that has a b. Specific examples include, but are not limited to, an on-off valve (two-way valve) 991A, a regulator 991B, a pressure gauge 991C, an on-off valve (three-way valve) 991D, and a mass flow controller 991E. The introduction pipe 993 is connected to a flow path port on the upstream side of the above-mentioned flow path (not shown).
The present invention is applicable to the above-mentioned mass flow controller 991E.

Next, the semiconductor manufacturing apparatus of the present invention will be described.
FIG. 6 is a block diagram of a semiconductor manufacturing apparatus according to an embodiment of the present invention.
The semiconductor manufacturing apparatus 1000 shown in FIG. 6 is an apparatus for executing a semiconductor manufacturing process by the ALD method (ALD: Atomic Layer Deposition Method), 300 is a process gas supply source, and 400 is an MFC 1 according to the present embodiment. A gas box, 500 is a tank, 600 is an on-off valve, 610 is a control unit, 700 is a processing chamber, and 800 is an exhaust pump.

In the semiconductor manufacturing process by the ALD method, it is necessary to precisely adjust the flow rate of the processing gas, and it is also necessary to secure the flow rate of the processing gas to some extent by increasing the diameter of the substrate.
In the gas box 400, various fluid devices such as an on-off valve, a regulator, and the MFC1 of the present embodiment are integrated and housed in the box in order to supply the accurately weighed process gas to the processing chamber 700.
The tank 500 functions as a buffer for temporarily storing the processing gas supplied from the gas box 400.
The on-off valve 600 controls the flow rate of the gas measured by the gas box 400.
The control unit 610 controls the on-off valve 600 to execute the flow rate control.
The processing chamber 700 provides a closed processing space for film formation on the substrate by the ALD method.
The exhaust pump 800 evacuates the inside of the processing chamber 700.

In the above application example, the case where the flow rate control device of the present invention is used in the semiconductor manufacturing process by the ALD method has been illustrated, but the present invention is not limited to this, and the present invention is, for example, an atomic layer etching method (ALE: Atomic Layer Etching). It can be applied to all objects that require precise flow rate adjustment, such as the law).

The present invention is not limited to the above-described embodiment. A person skilled in the art can make various additions and changes within the scope of the present invention.

1: Mass flow controller (MFC)
10: Body 11a: Inflow path 11b: Outflow path 12: Bypass flow path 13a: Sensor inflow path 13b: Sensor outflow path 14: Valve chamber 20: Flow sensor unit 21: Sensor base body 22: Sensor flow paths 23a, 23b: Heat generation Resistor 25: Resistance value detection circuit 28: Bridge circuit 30: Control unit 31: Amplifier 32: Comparison control unit 33: Aging control unit 40: Flow control valve 300: Process gas supply source 400: Gas box 500: Tank 600: Opening and closing Valve 610: Control unit 700: Processing chamber 800: Exhaust pumps 991A to 991E: Fluid equipment 992: Flow path block 993: Introduction pipe 1000: Semiconductor manufacturing equipment BS: Base plate G1: Longitudinal direction (upstream side)
G2: Longitudinal direction (downstream side)
P1 to P4: Connection point R: Resistance value R1, R2: Reference resistance Ra, Rb: Resistance value Ra-Rb: Resistance value difference Rs: Resistance value in thermal equilibrium state Rt: Resistance threshold SG1: Switching signal SG2: Completion signal SW: Switch Ve, Vn: Power supply voltage Vout: Output voltage W1, W2: Width direction

Claims (5)

It has a thermal flow rate sensor unit with a built-in heat generating resistor for measuring the mass flow rate of the fluid passing through the fluid flow path through which the fluid passes, and the mass flow rate of the fluid measured by the flow rate sensor unit is a predetermined value. It is a mass flow controller that controls the opening degree of the adjusting valve so as to adjust the flow rate of the fluid passing through the fluid flow path.
It has an aging management unit that manages whether or not the state of the flow rate sensor unit, which changes when the mass flow controller is activated and energizes the heat generating resistor and each part of the mass flow controller, becomes a flow rate measurable state.
Immediately after the mass flow controller is started, the aging control unit controls the calorific value of the heat generating resistor to a calorific value larger than the normal calorific value for flow rate measurement, and when a predetermined condition is satisfied, the heat generation control unit is used for the flow rate measurement. Mass flow controller that switches to the normal calorific value of. It further has a resistance value detection circuit for detecting the resistance value of the heat generating resistor.
The mass flow according to claim 1, wherein the aging management unit switches the heat generation amount of the heat generation resistor to the normal heat generation amount for measuring the flow rate when the resistance value detected by the resistance value detection circuit reaches a predetermined value. controller. After switching the calorific value of the heat generating resistor to the normal calorific value for measuring the flow rate, the aging management unit determines that the fluctuation of the resistance value is within a predetermined range, and then determines that the thermal state of the flow sensor unit is within a predetermined range. The mass flow controller according to claim 2, wherein the mass flow controller determines that the flow rate can be measured. It is a fluid control device in which multiple fluid devices are arranged.
The plurality of fluid devices are fluid control devices including the mass flow controller according to any one of claims 1 to 3. A semiconductor manufacturing apparatus using the mass flow controller according to any one of claims 1 to 3 for controlling the process gas in a semiconductor manufacturing process that requires a processing step with a process gas in a closed chamber.

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