JPH07310841A - Flow rate control method for fluid - Google Patents

Abstract

PURPOSE:To improve precision on control of a flow rate and to simplify control of the flow rate by a method wherein a flow rate of feeding fluid is controlled by regulating a pulse input signal applied on the piezoelectric element of a high speed opening and closing type valve from a control device and changing the duty ratio of pulse-form fluid flowing out from a high speed opening closing type valve. CONSTITUTION:In a control device 1, when a flow rate signal S1 is inputted or a set flow rate signal S2 is transmitted from a setter 1b, a pulse signal P1 corresponding to input signals S1 and S2 is inputted to a source device 1c from an oscillator 1a. Meanwhile, a pulse signal O1 corresponding to the pulse signal P1 or a puff signal O2 is inputted to the piezoelectric element drive part of a high speed opening closing type valve 3 from the source device 1c. When a high speed opening and closing type valve 3 is operated, a pulse-form gas flow A1 or a puff-form gas flow A2 is fed to a process chamber 2. In this case, when the pulse signal P1 is changed, a duty ratio (a) between the gas flows A1 and A2 is regulated and in this way, a flow of gas fed to the process chamber 2 is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly used for a device / equipment such as a semiconductor manufacturing device that requires highly accurate fluid flow rate control, and determines the pulse width and frequency of a pulsed fluid flow. The present invention relates to a fluid flow rate control method using a high-speed on-off type valve that enables automatic control of fluid flow rate with high accuracy without so-called hysteresis characteristics by adjustment.

[0002]

2. Description of the Related Art In a diffusion furnace of semiconductor manufacturing equipment,
As shown in FIG. 7, it is necessary to supply a plurality of different gases A, B, and C to the process chamber (diffusion furnace) D at the same time or sequentially with small flow rates.
The supply flow rates of B and C are controlled by adjusting the opening degrees of the high speed opening / closing valves E _{1 to} E ₃ . In FIG. 7, F _{1 to} F ₃ are volume tanks, G _{1 to} G ₃ are pressure adjusting valves, and H is a vacuum pump.

In the gas supply system shown in FIG. 7, in order to control the flow rate with higher accuracy, the operating speed of the high-speed on-off valve E is increased so that the pulsed minute gas flows A, B, C are generated. It is necessary to enable distribution control of That is, in order to achieve more accurate flow rate control, the pulse width is about 20 to 100 msec and the pulse period is about 100 to 100.
It is an indispensable condition that a pulsed gas flow of about 0 msec can be easily obtained and that the flow rate control characteristic by the pulsed gas flow does not exhibit a so-called hysteresis phenomenon.

However, in the conventional semiconductor manufacturing apparatus and the like, as the high speed opening / closing type valve E, an air cylinder driven diaphragm type flow control valve of a type in which an air cylinder type actuator is assembled to a diaphragm type valve is used. Therefore, the frequency that can follow the pulsed operation is up to about 1 Hz as described later, and it is impossible to set the pulse width W of the gas flow to 500 msec or less. As a result, there is a drawback in that more accurate flow rate control cannot be achieved.

The conventional air cylinder drive type diamond
In the flam type high speed opening / closing type valve, as shown in FIG.
The hysteresis phenomenon will appear in the flow rate characteristics of
And it is impossible to avoid the occurrence of this hysteresis phenomenon.
Is. As a result, the same input is applied depending on the input signal application direction.
Gas flow rate V even with force signal value ₁, V₂Makes a difference to
Therefore, it cannot be said that highly accurate flow rate control is basically possible.
I have a problem.

[0006]

SUMMARY OF THE INVENTION The present invention is capable of forming the above-mentioned problem in the conventional flow rate control method using a high-speed on-off type valve, that is, forming a pulsed flow having a short pulse width. It is impossible, and it is not possible to control the flow rate with higher accuracy, and there is a problem that the flow rate control characteristic of the valve shows a hysteresis phenomenon and there is a limit to the improvement of control accuracy. By providing a fluid flow rate control method that enables extremely highly accurate control by changing the duty ratio α of the pulsed gas flow (α = time during which the pulsed gas flow flows / cycle of the pulsed gas flow). is there.

[0007]

SUMMARY OF THE INVENTION The present invention is a fluid supply system for supplying a fluid as a pulsed flow through a high-speed on-off type valve, wherein the high-speed on-off type valve drives a diaphragm valve body by a piezoelectric element. With the piezoelectric element driving type diaphragm valve, the pulse input signal applied from the control device to the piezoelectric element driving section of the high speed opening / closing valve is adjusted to adjust the duty ratio α of the pulsed fluid flowing out from the high speed opening / closing valve. The basic configuration of the invention is to control the flow rate of the supplied fluid by changing the flow rate.

[0008]

The pulse input gas O corresponding to the required flow rate is input from the control device to the piezoelectric element driving section of the high speed opening / closing type valve, so that the pulsed gas flow corresponding to the pulse input signal O is passed through the high speed opening / closing type valve. Is supplied to the gas supply target. By adjusting the frequency and pulse width of the pulse input signal O from the controller, the frequency and pulse width of the pulsed gas flow are changed, and the so-called duty ratio α of the pulsed gas flow is adjusted. The relationship between the duty ratio α and the gas flow rate has a linear characteristic without hysteresis because the shape of each pulsed gas flow is the same. The duty ratio α is set so that the frequency of the pulsed gas flow is 50
Since it can be increased up to about Hz, it is possible to adjust in a fine range. As a result, it becomes possible to control the flow rate at a higher speed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a process chamber 2 of a semiconductor manufacturing apparatus.
FIG. 2 shows a case where the flow rate control method of the present invention is applied to a gas supply system for a gas, and the flow of the gas A to be supplied to the process chamber, which is a gas supply target, is in the form of pulse A ₁ (or puff A ₂ ). The flow rate of the supply gas is controlled by adjusting the duty ratio α.

In FIG. 1, 1 is a control device, 2 is a process chamber to which a gas is to be supplied, 3 is a high-speed open / close type valve, 4 is a vacuum pump, and A is a supply gas. The control device 1 includes an oscillator 1a, a setting device 1b, a power supply device 1c, etc., and a desired flow control signal S ₁ is input from the process chamber 2 side. That is, the flow rate control signal S ₁ is input, or the set flow rate signal S is input from the setter 1b.
₂ is transmitted, the pulse signal P ₁ (or the puff signal P ₂ ) corresponding to the input signal S ₁ or the input signal S ₂ is input to the power supply device 1c from the oscillator 1a, and the pulse signal is output from the power supply device 1c. The pulse input signal O ₁ or the puff input signal O ₂ corresponding to the signal P ₁ (or the puff signal P ₂ ) is input to the piezoelectric element drive unit of the high-speed opening / closing valve 3 described later.

When the pulse input signal O ₁ or the puff input signal O ₂ is supplied from the power supply device 1c to the high speed opening / closing type valve 3 and the high speed opening / closing type valve 3 is operated by this, a pulsed gas flow A to the process chamber 2 is generated. ₁ (or puffed gas stream A ₂ ) is supplied. At this time, as will be described later, when the pulse signal P ₁ (or the puff signal P ₂ ) from the oscillator 1a is changed, the duty ratio α of the pulsed gas flow A ₁ or the puffed gas flow A ₂ is adjusted. The supply gas flow rate to the chamber 2 is controlled.

In the present invention, a signal or gas flow having a constant width W and a constant height H, such as the pulse signal P ₁ and the pulsed gas flow A ₁ in FIG. 1, is continuously generated. The case of repeated generation is called a pulse shape, and the signal P _{2 of} FIG.
A case where a signal or a gas flow having a constant width W and a constant height H, such as the gas flow A ₂ or the gas flow A ₂ , is intermittently generated is called a puff shape.

In the present invention, the pulsed gas flow A
The duty ratio α of ₁ is defined by α = time T _{O of} flowing fluid / period T × 100%. That is, in the pulsed gas flow A ₁ of FIG. 1, the time T _o during which the fluid flows is the pulse width W of the pulsed gas flow A ₁ , and the period T is the reciprocal of the repetition frequency f.

FIG. 2 shows an example of a high-speed on-off type valve used for implementing the present invention. In FIG. 2, 5 is a valve body having a valve seat, 6 is a diaphragm valve body, and 7 is a diaphragm valve body.
Is a presser adapter, 8 is a diaphragm presser, 9 is a presser guide, and 10 is a bonnet nut. Further, 11 is a piezo pedestal disposed above the diaphragm retainer, 12 is a ball, 13 is a piezoelectric element holding case, 14 is a piezoelectric element (piezo element), 15 is a lock nut, 16 is a positioning nut, and 17 is a ball. , 18 is a ball receiver, 19 is a case, 20 is a connector, and 21 is a cable.

That is, the high-speed on-off valve 3 has a diaphragm valve of a type in which a so-called diaphragm valve element 6 is directly brought into contact with a valve seat and is caused by elastic force of the diaphragm valve element 6, and a piezoelectric element type actuator. A piezoelectric element drive type diaphragm type valve in which the above is combined, and the operating stroke of the diaphragm valve body 6 is finely adjusted by changing the tightening amount of the positioning nut 16. Further, in the high-speed open / close type valve 3, the downward valve body actuating force exerted on the diaphragm retainer 8 due to the expansion of the piezoelectric element 14 is accurately aligned with the upper axis of the piezoelectric element 14 and the ball. Balls 17 and 18 are inserted between the receiver 18 and the piezo base 11 and the diamond frame retainer 8, respectively, whereby the operation of the diaphragm valve body 6 is stabilized. Further, in the high-speed open / close type valve 3, in order to avoid the fluctuation of the flow rate characteristic due to the temperature change, the holding case 13 of the piezoelectric element,
The materials of the former members are selected so that the overall thermal expansion coefficient of the positioning nut 16, the lock nut 15, etc. becomes equal to the overall thermal expansion coefficient of the ball receiver 18, the piezoelectric element 14, the piezoelectric receiver 11, etc. This prevents the occurrence of a flow rate error due to a change in ambient temperature.

Next, the process chamber 2 according to the present invention
The control of the flow rate of the supply gas to the will be described. FIG. 3 is a pulse input signal O _{1 in} the gas supply system of FIG.
It is a diagram showing the relationship between (or pulse signal P ₁ ) and pulsed gas flow A ₁ , and shows so-called input-flow rate response characteristics. That is, FIG. 3 is a normal-open type high-speed on-off type valve shown in FIG. 2, using a temperature of 20 ° C., a fluid N ₂ gas, a primary pressure of 0.4 kgf / cm ² , and a secondary pressure of 0 k.
gf / cm ² (open to the atmosphere), the pulse input signal O ₁ was measured at a frequency of 5 Hz, and the pulsed gas flow A _{1 having} substantially the same shape for each pulse input signal O ₁ . It can be seen that is occurring.

FIG. 4 is a diagram showing the relationship between the input voltage and the flow rate in the process of fully opening → fully closing and fully closing → fully opening the high speed on-off type valve 3 used in the test of FIG. Pulse input signal O ₁ frequency 10 Hz, primary side fluid pressure 1.0
It is measured under the conditions of kgf / cm ² , opening to the atmosphere on the secondary side, fluid N ₂ gas, and ambient temperature of 20 ° C. That is, the curve a in FIG. 4 shows the voltage-flow rate characteristic of the portion corresponding to A ₁₁ in FIG. 3, and the curve b shows the voltage-flow rate characteristic of the portion corresponding to A ₁₀ in FIG. They are shown respectively.

By the way, in the high-speed on-off valve 3 of the present invention, if the pulse input signal O ₁ or the pulse signal P ₁ has the same shape as shown in FIG. You get ₁ . Further, one pulse-shaped gas flow A ₁ includes portions having different flow rate characteristics as shown by curves a and b in FIG. 4, respectively. However, a pair of different flow rate characteristic portions represented by a and b are included. Are always equally included in each pulsed gas stream A ₁ . Therefore,
Α over the flow rate when changing the duty ratio α by varying the pulse input signal O ₁ or varying the pulse width W of the input signals P _1, or the frequency of the pulse input signal O ₁ or the input signal P ₁ The characteristic has a shape as shown in FIG. 5, which is a so-called linear characteristic.

That is, in FIG. 5, the solid line portion shows the case where the duty ratio α is 0 → 100%, and the dotted line portion shows the case where the above α is 100 → 0%. It will be in a state of overlapping. In other words, the relationship between the duty ratio α and the flow rate is a linear curve without hysteresis, and as a result, the flow rate can be controlled with extremely high accuracy by adjusting α. In addition, α- in FIG.
The flow rate characteristic curve is the one when tested under the same conditions as in FIG.

FIG. 6 shows the relationship between the frequency and the flow rate ratio of the conventional air cylinder drive type diaphragm type high speed opening / closing valve and the piezoelectric element drive type diaphragm type high speed opening / closing valve used in the present invention. Curve R is the former,
Curves J respectively show the latter characteristics. That is, when the pulse fluid A ₁ is circulated by operating the high-speed on-off valve, when the frequency of the pulse input signal O ₁ increases, the actuation of the actuator and the operation of the diaphragm valve body cannot follow the signal frequency, and the flow rate is increased. The ratio (measured flow rate value / theoretical calculated flow rate value) increases. For example, in the former case, if the frequency of the pulse input signal O ₁ exceeds 1 Hz, the flow rate ratio increases and the pulse-like operation of the valve does not follow, whereas in the latter case, the flow rate ratio reaches a constant value up to about 50 Hz. It can be seen that the valve follows pulsed actuation.

[0021]

According to the present invention, a piezoelectric element driving type diaphragm type valve is used as a high speed opening / closing type valve, and a pulse-shaped input signal is applied to the piezoelectric element from the control device so that the piezoelectric element can operate at high speed. Moreover, the diaphragm valve element is opened and closed by using a large driving force. Therefore, the operating performance of the high-speed on-off type valve is improved,
It becomes possible to follow high-speed operation up to about Hz,
By increasing the frequency of the pulsed gas flow, it is possible to easily obtain a pulsed gas flow having a small pulse width and no disturbance in the waveform. Further, each pulsed gas flow flowing through the high-speed on-off type valve always maintains a constant shape, and one pulsed gas flow always includes a rising part and a falling part of the gas flow as a pair. There is. for that reason,
The relationship between the duty ratio of the pulsed gas flow and the gas flow rate is a linear relationship without hysteresis. As a result, by adjusting the duty ratio α of the pulsed gas flow by changing the pulse width and period of the pulse input signal to the piezoelectric drive unit of the high-speed on-off valve, the gas flow rate, which is the total of the pulsed gas flow, can be adjusted. It becomes possible to control with extremely high precision.
Further, compared to the case of using a conventional air-driven high-speed opening / closing type valve, vibration noise during opening / closing operation is completely eliminated, and air piping is not required. Also has excellent practical utility. As described above, the present invention exerts a particularly excellent effect even in a gas supply system of a semiconductor manufacturing apparatus that requires the supply of a pulsed gas flow or the supply of a puffed gas flow for a short time. .

[Brief description of drawings]

FIG. 1 is a system diagram of a gas supply system to which a fluid flow rate control method according to the present invention is applied.

FIG. 2 is a vertical sectional view of a high-speed on-off type valve used in the present invention.

FIG. 3 is a diagram showing a relationship between a pulse input signal and a pulsed gas flow.

FIG. 4 is a diagram showing the relationship between the input voltage and the flow rate of the high-speed on-off type valve used in the present invention.

FIG. 5 is a relationship diagram of the duty ratio α and the flow rate of the high-speed on-off type valve used in the present invention.

FIG. 6 shows a frequency-flow rate ratio characteristic of a conventional air cylinder drive type diaphragm type high speed opening / closing valve and a piezoelectric element drive type diaphragm type high speed opening / closing type of the present invention.

FIG. 7 shows an example of a gas supply system using a conventional air cylinder drive type diaphragm type high speed on-off valve.

FIG. 8 shows flow rate characteristics of a conventional air cylinder drive type diaphragm type high speed on-off valve.

[Explanation of symbols]

A is gas, A ₁ is pulsed gas flow, A ₂ is puffed gas flow, α is duty ratio, S ₁ is flow control signal, S ₂ is set flow signal, P ₁ is pulse signal, O ₁ is pulse input Signal, P ₂ is a puff signal, O ₂ is a puff input signal, 1 is a control device, 1 a is an oscillator, 1 b is a setting device, 1 c is a power supply device, 2
Is a gas supply target (process chamber), 3 is a high-speed open / close type valve, 4 is a vacuum pump, 5 is a valve body, 6 is a diaphragm valve body, 7 is a presser adapter, 8 is a diaphragm presser, 9 is a presser guide, and 10 is a bonnet. nut,
11 is a piezo pedestal, 12 is a ball, 13 is a piezoelectric element holding case, 14 is a piezoelectric element, 15 is a lock nut, 16
Is a positioning nut, 17 is a ball, 18 is a ball receiver,
19 is a case, 20 is a connector, and 21 is a cable.

Claims (3)

[Claims] 1. A fluid supply system for supplying a fluid as a pulsed flow through a high-speed on-off type valve, wherein the high-speed on-off type valve drives a diaphragm valve body by a piezoelectric element. In addition, the pulse input signal applied from the control device to the piezoelectric element driving unit of the high-speed opening / closing valve is adjusted, and the duty ratio α of the pulsed fluid flowing out from the high-speed opening / closing valve is adjusted.
A flow rate control method for a fluid, wherein the flow rate of the fluid to be supplied is controlled by changing the flow rate. 2. The fluid flow control method according to claim 1, wherein the duty ratio α of the pulsed fluid is changed by changing the period T of the pulse input signal. 3. The fluid flow rate control method according to claim 1, wherein the duty ratio α of the pulsed fluid is changed by changing the pulse width W of the pulse input signal.