JP2802246B2 - Flow control valve with delay compensation function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control valve used for a gas supply device in a semiconductor integrated circuit manufacturing facility, and more particularly to a flow control valve for compensating for a response delay of a flow meter at the start of gas supply. The present invention relates to a flow control valve with a delay compensation function that can eliminate waste.

[0002]

2. Description of the Related Art A semiconductor integrated circuit is manufactured by forming a fine circuit on a semiconductor substrate (hereinafter, referred to as a "wafer") by repeating a fine processing step and a film forming step. There are many devices that use special gases as devices for performing the various semiconductor manufacturing processes. For example, a corrosive gas such as a chlorine-based gas is used in a dry etching device among microfabrication devices. Alternatively, chemical vapor deposition (hereinafter, referred to as a chemical vapor deposition) for forming an interlayer insulating film and a gate electrode in the film forming process.
In a “CVD” apparatus, silane (SiH ₄ ), phosphine (PH ₃ ), diborane (B ₂
H ₆₎ to use special materials gas such. Hereinafter, these devices are collectively referred to as gas using devices.

In these gas-using apparatuses, a wafer is placed in a tank for performing a predetermined process, and heating, plasma application, and the like are performed as necessary while a predetermined gas flows at a predetermined flow rate. . Here, when supplying gas to the processing tank, as shown in FIG. 20, a filter 71, a pressure regulating valve 72, a pressure sensor 73, and a flow rate controller 75 are provided between a gas source 70 for supplying gas and the processing tank 74. Arrange. The flow controller 75 has a built-in flow sensor. Then, shut-off valves 76, 77, 78 are arranged before the pressure sensor 73 and before and after the flow controller 75. In such a gas line, a constant flow rate of gas can be stably supplied by feeding back the output value of the built-in flow sensor by the flow controller 75. With such a system, it is possible to set the pressure and flow rate of the supply gas to the processing tank and to stop the supply.

However, in a gas-using apparatus, it is rare to use only one kind of gas, and it is common to use two or more kinds of gases at the same time. For example, when a silicon oxide film is formed by a plasma CVD apparatus, in addition to silane as a silicon source, dinitrogen monoxide N ₂ O gas as an oxygen source and hydrogen H ₂ for accelerating the reaction and preventing unnecessary oxidation are used. The gas and the nitrogen N ₂ gas for dilution are used simultaneously. Therefore, a gas supply system as shown in FIG. 20 is also required according to the number of types of gas used.

[0005]

However, the above-mentioned flow sensor and flow controller have the following problems. That is, the flow rate sensor that detects the gas flow rate does not always have excellent responsiveness to a change in the measured flow rate. Therefore, when starting the gas supply, there is a slight delay from when the gas starts flowing until the flow sensor actually outputs a constant flow value.

For this reason, the control circuit of the flow controller 75 receiving the feedback of the output value recognizes a flow value lower than the actual flow immediately after the start of gas supply. Will be increased excessively. Therefore, the actual flow rate of the gas will overshoot once and then settle to a predetermined flow rate as shown in FIG.

Therefore, there is a considerable delay from when the shut-off valve 76 or the like is opened to start gas supply to when the gas at the set flow rate actually flows stably. The gas flowing during this time delay is different from the set flow rate.
Abnormal process characteristics such as film quality and etch rate.
In order to avoid this, the process is performed after the gas flow rate is stabilized, so that the gas during the time delay flows unnecessarily without being used in the process.

In addition, such delay characteristics vary depending on the type of gas to be supplied, and there are individual differences in the flow rate sensor itself. Therefore, when a plurality of gases are supplied, as shown in FIG. 10, other gases must be flowed wastefully until the gas d having the largest delay in each gas supply system is stabilized. is there. FIG. 10 is a graph showing the change over time of the flow sensor output value of each gas after opening the shutoff valve 76 and the like. Here, it takes about 4 seconds until the flow rate of the gas d is stabilized.

Here, gas use apparatuses can be roughly classified into two types according to the mode of wafer processing. One is a so-called batch type process in which a processing tank is formed large and about 50 wafers are simultaneously placed in the tank to perform processing, and a low-pressure CVD apparatus or the like corresponds to this. Another one
One is a so-called single-wafer processing in which only one or two wafers are placed in a tank and processing and wafer exchange are sequentially performed.
A VD device or the like corresponds to this.

[0010] Whereas batch processing is characterized by high productivity, single wafer processing is characterized by processing uniformity between wafers (eg, film thickness, etc.). In recent years, with the further miniaturization of circuit elements and the need for more uniformity of film thickness and the like, the specific gravity of single-wafer processing is gradually increasing. In such single-wafer processing, wafer exchange is performed each time processing is performed. When replacing the wafer, the supply of the process gas is once stopped, the processing tank is purged with nitrogen gas or the like, the processing tank is opened, the wafer is replaced, and then the supply of the process gas is started again. Most of the process gas is highly toxic and spontaneously combustible and extremely dangerous, so that it is not allowed to flow out of the apparatus. Of course, this series of operations is usually automated.

Therefore, in the case of single-wafer processing, the number of times of starting the supply of the process gas becomes extremely large, and each time, the above-mentioned response delay waiting time of the mass flow controller occurs. For this reason, time loss is large, which is an obstacle to improving productivity. Further, the amount of gas flowing wastefully becomes too large to ignore. This naturally leads to an increase in cost because the process gas is expensive.
Furthermore, since the harmful process gas after use is not released to the environment as it is, an extra load is also applied to the abatement apparatus provided in the exhaust system.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-described problems. In a flow control valve which performs flow control according to an output value of a flow meter, a response delay of the flow meter at the start of gas supply is reduced. By providing delay compensation means for compensation, it is possible to supply a predetermined gas accurately without wasting response stabilization wait time and gas consumption, and therefore, excellent delay compensation function with high productivity and no extra burden on the gas exhaust system It is an object of the present invention to provide an attached flow control valve.

[0013]

In order to achieve the above object, a flow control valve (1) with a delay compensation function according to the present invention is a flow control means for adjusting a flow rate of a gas, and measures an actual flow rate of the gas. A flow control valve having a flow meter and controlling a flow rate adjusting means based on an output value of the flow meter, and a delay compensating means for compensating for a time delay of a change in the output value of the flow meter.

Further, in the flow control valve (2) having a delay compensation function according to the present invention, the delay compensation means may use a plurality of first-order delay functions having different time constants in combination with the time delay of the output value change of the flow meter. Is compensated for. Further, the flow control valve with delay compensation function (3) of the present invention is characterized in that the delay compensation means compensates for a time delay of a change in the output value of the flow meter using one primary delay function. is there.

[0015]

In the flow control valve (1) with the delay compensation function of the present invention having the above-described structure, the flow rate adjusting means is controlled by the output value of the flow meter to maintain a predetermined flow rate during steady gas supply. At the start of gas supply, because of the responsiveness of the flow meter, the change in the flow meter output value is temporally delayed from the change in the actual flow rate.
The delay compensating means compensates for this and sends a signal that has canceled the response delay to the flow rate adjusting means. Thereby, the gas flow rate is stabilized early after the gas supply is started.

In the flow control valve with delay compensation function (2) of the present invention, the delay compensation means cancels the response delay by using a plurality of first-order delay functions having different time constants. As soon as the gas flow rises,
Stabilizes to a predetermined value. In the flow control valve with delay compensation function (3) of the present invention, the response delay is canceled by using one first-order lag function, so that the gas flow rate rises immediately after the start of gas supply.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying a flow control valve with a delay compensation function of the present invention will be described below with reference to the drawings. In FIG.
1 is a cross-sectional view illustrating a configuration of a flow control valve 1 with a delay compensation function according to a first embodiment. The flow control valve 1 with a delay compensation function has a flow meter section 2 on the left side and a solenoid valve section 3 on the right side.

The flow meter section 2 has an input port 32 opened on the left side of the main passage 27. Further, a columnar member 35 is held at a central portion of the main passage 27 at a predetermined interval from the inner wall. An inlet 23a and an outlet 23b are opened on inner walls on both sides of the columnar member 35, and a conduit 23 is provided.
The heat-sensitive coils C1 and C2 are adhered to the upstream and downstream sides of the conduit 23 through which the gas F flows by a UV curable resin or the like. The heat-sensitive coils C1 and C2 are formed by winding a pair of self-heating type thermometers each having a large temperature coefficient, and have the same resistance value.

The thermosensitive coils C1 and C2 are connected to a constant temperature control circuit 24. The constant temperature control circuit 24 includes a bridge circuit including the heat-sensitive coils C1 and C2, and controls the flow rate of the gas F flowing through the conduit 23 between the bridge circuits while controlling the temperature of the heat-sensitive coils C1 and C2 to a constant value. It is calculated from the potential difference.

The solenoid valve section 3 is a section for adjusting the gas flow rate. At the center thereof, there is a coil 28 in which a copper wire is wound around the body of a hollow cylindrical coil bobbin 29. Further, a leaf spring 34 having a through hole formed on the right side of the hollow portion of the coil bobbin 29 is fixed to an inner wall surface and holds a movable valve body 30. An output port 33 is formed on the right side of the valve body 30. Further, a valve seat 31 that connects the input port 32 and the output port 33 is provided at a position opposing the valve body 30. Further, the solenoid valve drive circuit 26 is connected to the coil 28. The solenoid valve drive circuit 26 is connected to the flow rate control circuit 25 via the delay compensation circuit 5, and the flow rate control circuit 25 is connected to the constant temperature control circuit 24.

Next, the operation of the flow control valve 1 with the delay compensation function will be described. When the gas F flows from the input port 32 to the output port 33, the gas F flows inside the conduit 23 and the main passage 27.
And the flow ratio is constant. On the other hand, the thermosensitive coils C1 and C2 are controlled by the constant temperature control circuit 24 so that their temperatures are always equal and constant. At this time, since heat is transferred from the heat-sensitive coils C1 to C2 by the gas F flowing through the conduit 23, the heat-sensitive coils C1
Is applied with a larger voltage to generate more heat. The difference between the voltages applied to the heat-sensitive coils C1 and C2 is proportional to the flow rate of the gas F. Then, the constant temperature control circuit 24 outputs this voltage difference to the flow rate control circuit 25 by an internal bridge circuit.

Then, the flow rate control circuit 25
Calculates the flow rate. Since such a flow rate value includes a time delay with respect to the actual flow rate change of the gas F, the solenoid valve driving circuit is configured to obtain the required flow rate after the time delay is compensated by the delay compensation circuit 5. 26 is transmitted as a flow rate command. This delay compensation action will be described later. The solenoid valve drive circuit 26 that has received the flow rate command adjusts the opening of the solenoid valve section 3 so that the commanded flow rate flows. Then, when the flow rate is flowed for a predetermined time, the flow of the gas F is shut off by shutting off the power supply to the electromagnetic valve unit 3 and closing the valve. Thereby, the gas F of a predetermined total flow rate is sent.

FIG. 2 shows a flow control valve 1 with a delay compensation function.
FIG. 1 is a conceptual diagram showing a configuration of a gas supply system that uses the present invention. In FIG. 2, a gas, which is appropriately depressurized by a regulator 12, is supplied from a gas source 10 for storing the gas through a conduit 22 to a processing tank 74 through a flow control valve 1 with a delay compensation function. In the conduit 22, the filter 11 is provided before the regulator 12, the pressure gauge 16 is provided between the regulator 12 and the flow control valve 1 with the delay compensation function, and the gas flow is restricted to the downstream of the flow control valve 1 with the delay compensation function. Needle valve 15
Each is provided. Further, stop valves 17, 18, 14 are arranged at the subsequent stages of the regulator 12, the pressure gauge 16, and the needle valve 15, respectively. The stop valve 14 is opened and closed by the compressed air 21 for operation.
And a switch 19 for applying a signal to the solenoid valve 20.

In the system shown in FIG. 2, an XY decoder 4 is provided. The XY decoder 4 monitors the output from the flow control circuit 25 or the delay compensation circuit 5 of the flow control valve 1 with the delay compensation function. It is provided especially for measuring. Further, the electric signal applied by the switch 19 is also monitored by the XY decoder 4. In such a gas supply system, the needle valve 15 and X
The -Y decoder 4 is particularly added to measure the effect of the delay compensation circuit 5 of the flow control valve 1 with a delay compensation function, and is not required when used as a normal gas supply system.

Next, the measurement of the delay characteristic of the flow rate value and the effect of the delay compensation circuit 5 in the flow control valve 1 with the delay compensation function will be described. In order to measure the delay characteristic of the flow value in the flow control valve 1 with the delay compensation function, the gas supply flow rate must first be set. The setting of the gas supply flow rate is performed according to the following procedure.

First, after confirming that the stop valve 14 is closed, the main valve of the gas source 10 is opened and the regulator 12 is opened.
Apply the original pressure to In this measurement, stop valves 17, 18
Is always open. Then, the regulator 12 is set to a predetermined pressure (here, 1 kgf / cm ² ). Next, the solenoid valve portion 3 of the flow control valve 1 with the delay compensation function is fixed in a fully open state. Then, the cutoff valve 14 is opened, and the needle valve 15 is adjusted so that a predetermined flow rate (here, 375 sccm) flows. Since the setting of the gas supply flow rate is completed as described above, the shut-off valve 14 is closed once.

Then, the delay characteristic is measured. First, a pure delay characteristic of the flow value in the flow meter unit 2 is measured in the following procedure. The delay compensating circuit 5 is made to pass through, and the electromagnetic valve section 3 is kept in a fully opened state. Then, the shut-off valve 14 is opened, and the subsequent output value of the flow control circuit 25 is output from the XY decoder 4. An example of the measured value at this time is shown as a curve a in the graph of FIG. In curve a, the flow control circuit 25
It can be seen that it took about 4 seconds for the output value to settle to the predetermined flow rate.

Such a delay is a response delay of the output value of the flow control circuit 25 to the actual flow rate. Since it is considered that this delay largely includes a primary delay element, this is assumed to be a superposition of the primary delay element and other delay elements. The first-order lag element is represented by E (s), and the other lag elements are referred to as “transfer functions not clarified” since the transfer functions are not clarified, and are represented by F (s). In this embodiment, assuming that the contribution of the delay element F (s) is small, the first-order delay element E (s) is compensated to compensate for the entire delay. The first-order lag E (s) is expressed by the following equation. E (s) = 1 / (1 + s * τ ₁ ) Here, τ ₁ represents a time constant of a response of the flow control circuit 25, and s represents a complex function called a Laplace operator.

Considering this in the conceptual diagram of FIG.
_The output V _O (s) with respect to _I (s) appears as a curve a. Therefore, by turning on the delay compensation circuit 5, this is compensated and the output V _OUT (s) is obtained. here,
The transfer function of the delay compensation by the delay compensation circuit 5 is given by G (s) = {1 + s * (a + τ ₂ )} / (1 + s * τ ₂ ) (1) Here, if a circuit is further configured so that a + τ ₂ = τ ₁ (2), the following equation is obtained. G (s) = (1 + s * τ 1) / (1 + s * τ 2) (3)

Therefore, FIG. 5 can be represented as shown in FIG. Further, from the equations (1) and (3), since E (s) * G (s) = 1 / (1 + s * τ ₂ ), FIG. 6 can be rewritten as shown in FIG.

As a result, the time constant τ ₁ of the first-order lag response of the flow rate control circuit 25 is canceled by the lag compensation circuit 5, resulting in a first-order lag response of a new time constant τ ₂ . Here, since the condition for canceling is equation (2), if a = 0.9 * τ ₁ (4), then τ ₂ = 0.1 * τ ₁ (5), and τ ₂ is τ _One tenth of one.

Next, the transfer function G (s) of the delay compensation circuit 5 is shown in a block diagram. If the input is X and the output is Y,
Equation (3) shows the following equation. Y = {(1 + s * τ 1) / (1 + s * τ 2)} * X deform _{it, Y + s * τ 2 *} Y = X + s * τ 1 * X Y = X / (s * τ 2) -Y / (S * τ ₂ ) + X * (τ ₁ / τ ₂ ) Y = X + {(τ ₁ −τ ₂ ) * X− (Y−X) / s} / τ ₂ , from which the block line in FIG. The figure is obtained.

This block diagram is realized, for example, as an analog circuit as shown in FIG. This circuit is an example in which the compensation circuit 5 is realized using three differential input type operational amplifiers. That is, the non-inverting amplifier circuit is formed by the operational amplifiers A1 and A2, and the inverting amplifier circuit is formed by the operational amplifier A3. In this circuit, the input signal V1 is set to P1
Branch at one point, one of which is connected to the +
The other is input to the input terminal, and the other is input to the + input terminal of the operational amplifier A2 via the resistors R1 and R3. The point P3 between the resistors R1 and R3 is grounded via the resistor R2.

The output terminal of the operational amplifier A1 is the output signal V1.
0, and the resistance of the operational amplifier A1 via the resistor R11.
Input to the input terminal. The negative input terminal of the operational amplifier A1 is grounded via the resistor R10. The output of the operational amplifier A2 is input to the + input terminal of the operational amplifier A1 via a resistor R8, and the operational amplifier A is supplied via a resistor R6.
2 input terminal. Also, the operational amplifier A2
The input terminal is grounded via a resistor R5.

Then, the output of the operational amplifier A2 is branched at the point P4, and is inputted to the minus input terminal of the operational amplifier A3 via the resistor R7. In the operational amplifier A3, the negative input terminal and the output terminal are connected via the capacitor C, and the positive input terminal is grounded. The output of the operational amplifier A3 is input to the + input terminal of the operational amplifier A2 via the resistor R4. In this circuit, if the time constant of the first-order lag to be compensated is 1 s, the resistance value of each resistor and the capacitance of the capacitor are 1 kΩ for R1 and R5, 9 kΩ for R2, R3,
R4 is 47 kΩ, R6 is 19 kΩ, R7 is 500 kΩ,
R8 to R11 are 10 kΩ. And R4 and R6
Is 2 μF.
It is.

Next, the circuit diagram of FIG. 3 is verified. Assuming that the input potential is V1, the potential V2 at the point P3 is V2 = V1 * {R2 / (R1 + R2)} according to Ohm's law. Since R1 is 1 kΩ and R2 is 9 kΩ, V2 = 0. .9 * V1 (6) Also, the potential V5 of the negative input terminal of the operational amplifier A3
Is imaginarily short-circuited to the ground, so that V5 = 0. Therefore, the current I1 flowing through the resistor R7 is given by I1 = V7 / R7 (7) where the potential at the point P4 is V7.

Further, regarding the charge Q of the capacitor C,
Assuming that the output terminal potential of the operational amplifier A3 is V4, Q = −V4 * C. On the other hand, since it is also the integrated value of the current I1, Q = ∫I1dt, and V4 is obtained from these. V4 = − (1 / C) * ∫I1dt (8)

By substituting equation (7) into equation (8), V4 =-{1 / (C * R7)} * ∫V7dt, which is expressed using the Laplace operator s, V4 =-{1 / (C * R7)} * V7 * (1 / s) is obtained. In this case, since C is 2 μF and R7 is 500 kΩ, this equation becomes: V4 = −V7 / s (9)

Then, the potential V3 of the + input terminal of the operational amplifier A2 is expressed as follows: V3 = (V2-V4) * {R4 / (R3 + R4)} + V4. Since R3 is equal to R4 as described above, V3 = (V2 + V4) / 2 (10) is obtained. Since V3 is equal in potential to the negative input terminal potential V6 of the operational amplifier A2 due to the imaginary short, V3 = V6, and the current I2 flowing through the resistor R5 is obtained from this equation. I2 = V6 / R5 = V3 / R5 (11)

On the other hand, since I2 is equal to the current flowing through the resistor R6, I2 = (V7−V6) / R6 = (V7−V3) / R6, and the following equation is obtained by substituting the equation (11). Can be V7 = V3 * {1+ (R6 / R5)} As described above, since R6 is 19 kΩ and R7 is 1 kΩ, this equation becomes: V7 = 20 * V3 (12)

Next, the potential V8 at the point P2 is given by: V8 = (V1-V7) * {R8 / (R8 + R9)} + V7 Since R8 and R9 are equal as described above, the potential is obtained as follows: . V8 = (V1 + V7) / 2 (13) And V8 is an operational amplifier A due to an imaginary short.
V8 = V9 since the negative input terminal potential V1 is equal to V9. Therefore, the current I3 flowing through the resistor R10 is I3 = V9 / R10 = V8 / R10 (14)

Since I3 is equal to the current flowing through the resistor R11, I3 = (V10-V9) / R11 = (V10-V8) /
R11, and substituting equation (14) into the equation, V10 = V8 * {1+ (R11 / R10)}. Since R10 is equal to R11 as described above, V10 = 2 * V8 (15) is obtained. .

Next, V7 = 10 * (V2 + V4) is obtained from the equations (10) and (12), and V7 and V7 are obtained from the equations (6) and (9).
The relational expression with 1 is as follows: V7 / V1 = 9 / {1+ (10 / s)} (16) On the other hand, from the expressions (13) and (15), when V8 is deleted, the following expression is obtained: V10 = V1 + V7. Then, according to this equation and equation (16), V7
Is eliminated, V10 / V1 = (1 + s) / {1+ (s / 10)} (17), which is the transfer function of the delay compensation circuit 5, that is, G
(s) is shown.

Therefore, it can be seen from the comparison between the equations (3) and (17) that τ ₁ = 1 (18) τ ₂ = 1/10 (19). Here, equation (1) is replaced with equation (4),
By substituting the equations (5), (18), and (19), the equation (17) is obtained, and thus it can be seen that the equation (17) is correct.

As described above, the delay compensation circuit 5 compensates for the response delay of the output of the flow control circuit 25 and feeds it back to the solenoid valve drive circuit 26. The curve b in FIG. 8 shows the output in which the response delay is compensated by the delay compensation circuit 5 using a first-order delay function of τ ₁ = 1.22 sec. It can be understood that the response is settled to a constant value with a much shorter response time than the curve a in FIG. 8 in which the response delay is not compensated. For this reason, in the flow control valve 1 with the delay compensation function, the rise at the start of gas supply is much faster than in the conventional flow control valve without the delay compensation circuit.

Therefore, by using the flow control valve 1 with the delay compensation function of the present embodiment in a system using many kinds of gases, as shown in FIG. And reduce the response waiting time. In FIG. 9, all the gas flow values have reached the predetermined values within one second.

In the curve b of FIG. 8, after the output value reaches the predetermined value early (point Q), the output value slightly decreases for a while. This is because the actual rise of the flow rate cannot be completely corrected. This will be described with reference to the graph of FIG. A curve f shows an actual output from the mass flow sensor (flow meter unit 2) of the flow control valve 1 with the delay compensation function. On the other hand, curve g is τ
₁ shows a first-order lag function of 1.22 sec. Immediately after the rise, the curve g and the curve f agree well, but j
There is a difference in the part. This is the cause of the output decrease after the point Q in the curve b in FIG.

When a time constant is set so as to approach the vicinity of the convergence portion of the curve f (τ ₁ = 1.76 sec: curve h), the stability becomes faster. However, the compensated output at this time is shown in FIG.
Overshoot (n) as shown by curve m in FIG. Note that curve a in FIG. 12 is the same as curve a in FIG. This can be solved by the second embodiment described below.

Next, a second embodiment of the present invention will be described. The second embodiment has substantially the same configuration as the first embodiment, except that a delay compensation circuit performs compensation approximated by a first-order parallel delay function. Therefore, only the delay compensation function will be described. First, the first-order parallel delay is a delay that is expressed as a result that an input signal is bisected in parallel as shown in FIG. 13, receives first-order delays having different time constants, and combines them. The transfer function J (s) of the first-order parallel delay is expressed by the following equation. J (s) = α / (1 + s * τ ₃ ) + β / (1 + s * τ ₄ ) (21) Here, α and β are distribution ratios to respective components and are both positive.
Also, α + β = 1. τ ₃ and τ ₄ are time constants of each component.

Therefore, in order for the delay compensating circuit to completely cancel this, the transfer function of the delay compensating circuit is expressed by J (s) ⁻¹ = {(1 + s * τ ₃ ) * (1 + s * τ ₄ )} / { 1 + s *
(α * τ ₄ + β * τ ₃ )}, but complete cancellation is not possible due to the difficulty of complete differentiation. Therefore, the transfer function of the delay compensation circuit is set to K (s), and when J (s) is canceled by K (s), the transfer function becomes a first-order delay function having a very small time constant. That is, J (s) * K (s) = 1 / (1 + s * τ ₀ ) (22) Here, it is assumed that the time constant τ ₀ is sufficiently smaller than τ ₃ and τ ₄ .

Here, if α * τ ₄ + β * τ ₃ = τ ₅ , J (s) in the equation (21) is as follows. J (s) = (1 + s * τ 5) / {(1 + s * τ 3) * (1 + s *
τ ₄ )} When this is used to represent K (s) in equation (22), K (s) = {(1 + s * τ ₃ ) * (1 + s * τ ₄ )} / {(1 + s * τ)
₅ ) * (1 + s * τ ₀ )} is obtained. For convenience, K (s) = K ₁ (s) * K ₂ (s), and K ₁ (s) = (1 + s * τ ₃ ) / (1 + s * τ ₅ ) (23) K ₂ (s) = ( 1 + s * τ ₄ ) / (1 + s * τ ₀ ) (24)

Next, this is shown in a block diagram. K ₁ (s)
Since K ₂ (s) is formally the same as K ₂ (s), K ₁ (s) will be considered. Assuming that the input is X and the output is Y, Y = {(1 + s * τ ₃ ) / (1 + s * τ ₅ )} * X, which is transformed as in the following equation. Y = [{(XY) / s} + τ ₃ * X] / τ ₅ Thus, the block diagram of FIG. 14 is obtained. K ₂ (s)
Therefore, if the input is Y (the output of K ₁ (s)) and the output is Z, a block diagram of the entire K (s) is as shown in FIG. To realize this as an analog circuit,
For example, the one shown in FIG. 16 can be considered.

In this circuit, a portion corresponding to K ₁ (s) mainly composed of an operational amplifier A4 and a portion equivalent to K ₂ (s) mainly composed of an operational amplifier A5 are connected in series. The input signal X is input to the + input terminal of the operational amplifier A4 via a parallel connection of the resistor R12 and the capacitor C3. The + input terminal of the operational amplifier A4 is grounded via the resistor R13. In the operational amplifier A4, the output terminal and the − input terminal are connected via the resistor R15.
The input terminal is grounded via a resistor R14.

The output of the operational amplifier A4 is connected to the resistor R1.
6 and a capacitor C4 in parallel with an operational amplifier A5
Is input to the + input terminal. The + input terminal of the operational amplifier A5 is grounded via the resistor R17. Operational amplifier A
In 5, the output terminal and the -input terminal are connected via a resistor R19, and the -input terminal is grounded via a resistor R18. Then, the output of the operational amplifier A5 becomes the output signal Z.

The relationship between input and output signals of a portion corresponding to K ₁ (s) of this circuit is obtained. First, the following equations hold for the potential V11 of the + input terminal of the operational amplifier A4. X-V11 = I4 * R12 (25) X-V11 = (1 / C3) * ∫I5dt (26) Here, I4 is a current flowing through the resistor R12, and I5 is a current flowing through the conductor of the capacitor C3. When the equation (26) is rewritten using the Laplace operator s, (X−V11) = (1 / C3) * I5 * (1 / s) (27)

The sum of I4 and I5 becomes the current I6 flowing through the resistor R13, and I6 = V11 / R13 holds, so the following equation holds from the equations (25) and (27). V11 / R13 = (X−V11) / R12 + s * C3 *
(X-V11) From this, V11 is obtained. _{V11 = (R M / R12)} * {(1 + s * C3 * R12) / (1 + s * C3 * R M)} * X (28) where and a _{= R M (R12 * R13)} / (R12 + R13).

On the other hand, the potential V12 of the negative input terminal of the operational amplifier A4 is expressed by the following equation, with the current flowing through the resistors R14 and R15 being I7. V12 = I7 * R14 (29) And the following relationship holds for the potential V13 of the output terminal. V13 = V12 + I7 * R15 From this equation and equation (29), V13 = {(R14 + R15) / R14} * V12 is derived. Since V12 is equal to V11 due to the imaginary short, V13 = {(R14 + R15) / R14} * V11 is obtained.

By substituting equation (28) into this, the following equation is obtained. V13 = B * {(1 + s * C3 * R12) / (1 + s * C3 *)
In R _M)} * X here was B = {(R14 + R15) / R14} * (R M / R12) = {(R14 + R15) / R14} * {R13 / (R12 + R13)}. The necessary and sufficient conditions for B to be 1 are R13 and R14
Is equal and R12 and R15 are equal, so if such a circuit is constructed, V13 will be as follows: V13 = {(1 + s * C3 * R12) / (1 + s * C3 * _RM )} * X (30) Becomes

Based on the same considerations for the portion corresponding to K ₂ (s), if a circuit is formed so that the resistors R17 and R18 and the resistors R16 and R19 are equal, Z = {(1 + s * C4 * R16) / (1 + s * C4 * R _N )} * V13 (31) is obtained. Here, an _{R N = (R16 * R17)} / (R16 + R17).

From equations (30) and (31), (23)
Τ ₃ and τ _{5 in} the equation and τ ₄ and τ _{0 in the} equation (24) are obtained as follows. τ ₃ = C 3 * R 12 τ ₄ = C ₄ * R 16 τ ₅ = C 3 * R _M τ ₀ = C 4 * R _N By compensating for the first-order parallel delay by selecting each element and forming a circuit so as to satisfy these. A circuit is realized.

Here, α = 0.06, β = 0.94, τ ₃
= 7.8 sec, τ ₄ = 1.1 sec, τ ₀ = 0.01 sec
c and τ ₅ = α * τ ₄ + β * τ ₃ = 7.398 sec. A circuit is created and the result of delay compensation is shown in FIGS. 18 and 19. FIG. 19 is an enlarged view of the time axis of FIG. The output after the compensation rises quickly and the output after the rise does not decrease. This is shown in FIG.
This is because, as shown in the graph, the actual output value (solid line) of the mass flow sensor and the waveform of the first-order parallel delay (broken line) match very well. Therefore, by applying this to a gas using device, the flow rate can be raised and stabilized in a short time after the start of gas supply.

As described in detail above, in the flow control valve 1 with the delay compensation function of the present embodiment, the delay compensation circuit 5 compensates for the response delay of the output of the flow meter unit 2 at the start of gas supply, and The flow rate is stabilized in a short time after the start of gas supply. For this reason, unnecessary gas outflow during the stabilization waiting time immediately after the start of gas supply can be significantly reduced. Thereby, productivity can be improved and the load on the gas exhaust system can be reduced. In particular, when the present invention is applied to a gas supply system to a process apparatus that performs a single-wafer processing in which the frequency of the gas supply start operation is high, the effect is large.

The above embodiments are not intended to limit the present invention in any way, and within the scope not departing from the gist of the present invention.
Of course, various modifications and improvements are possible. For example, in the flow control valve 1 with the delay compensation function shown in FIG. 1, the flow control circuit 25 and the delay compensation circuit 5 are separate circuits, but they may be integrated circuits. Also,
In the second embodiment, two types of first-order lag functions are arranged in parallel, but three or more types of first-order lag functions may be arranged in parallel.

In each of the above embodiments, the delay compensation circuit 5
However, when a microcomputer or the like is incorporated in the flow control valve, the same delay compensation function can be included in the software of the microcomputer to replace the analog circuit. Further, in each of the above embodiments, the portion for adjusting the flow rate is constituted by the solenoid valve, but may be constituted by something other than the solenoid valve. Further, the flow meter section is constituted by the heat-sensitive coil, but may be constituted by other means.

[0065]

As apparent from the above description, according to the present invention, in the flow control valve for controlling the flow according to the output value of the flow meter, the delay compensation for compensating the response delay of the flow meter at the start of gas supply. Means, it is possible to supply a predetermined gas accurately without wasting response stabilization waiting time and gas consumption, and therefore, the flow rate with an excellent delay compensation function that is high in productivity and does not impose an extra burden on the gas exhaust system A control valve can be provided.

In particular, since the delay is compensated by using the first-order lag function, it is possible to provide a flow control valve with a delay compensation function which is excellent in the rise of the gas flow after the start of gas supply. Further, if the compensation is performed by paralleling a plurality of first-order lag functions having different time constants, it is possible to provide a flow control valve with a delay compensation function which is excellent in the rise of the gas flow rate and the stability of the gas flow rate thereafter. The present invention is particularly effective when applied to a gas supply system for an apparatus that uses many types of gases simultaneously or an apparatus that performs single-wafer processing.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a flow control valve with a delay compensation function of the present invention.

FIG. 2 is a conceptual diagram showing a configuration of a gas supply system using a flow control valve with a delay compensation function of the present invention.

FIG. 3 is a circuit diagram showing an example of a delay compensation circuit used in the flow control valve with a delay compensation function of the present invention.

FIG. 4 is a block diagram derived from the circuit diagram shown in FIG. 2;

FIG. 5 is a conceptual diagram showing signal transmission in a flow control valve with a delay compensation function.

FIG. 6 is a conceptual diagram showing signal transmission in a flow control valve with a delay compensation function.

FIG. 7 is a conceptual diagram showing signal transmission in a flow control valve with a delay compensation function.

FIG. 8 is a graph showing changes over time of output values of a flow meter and a delay compensation circuit.

FIG. 9 is a graph showing a change over time in a gas flow rate in a system using various kinds of gases by the flow control valve with a delay compensation function of the present invention.

FIG. 10 is a graph showing a change over time of a gas flow rate in a system using various kinds of gases by a conventional flow control valve.

FIG. 11 is a graph illustrating compensation of the output of a mass flow sensor by a first-order lag function.

FIG. 12 is a graph illustrating overshoot when a next-order constant is set so as to be stabilized early by a first-order lag function.

FIG. 13 is a conceptual diagram illustrating compensation by a first-order parallel delay.

FIG. 14 is a block diagram showing all stages of a first-order parallel delay compensation circuit;

FIG. 15 is a block diagram illustrating a first-order parallel delay compensation circuit.

FIG. 16 is an analog circuit that realizes a first-order parallel delay compensation circuit.

FIG. 17 is a graph showing a result of delay compensation by a primary parallel delay compensation circuit.

FIG. 18 is a graph showing a result of delay compensation by a primary parallel delay compensation circuit.

FIG. 19 is a graph showing a result of delay compensation by a primary parallel delay compensation circuit.

FIG. 20 is a conceptual diagram showing a conventional gas supply system.

FIG. 21 is a graph showing an overshoot of an actual gas flow rate in a conventional gas supply system.

[Explanation of symbols]

 1 Flow control valve 2 Flow meter section 3 Solenoid valve section 5 Delay compensation circuit

Continuing from the front page (72) Inventor Shinichi Nitta 3005 Hayasaki, Kogai-shi, Aichi Prefecture Inside Hayasaki Shikadi Co., Ltd. (56) References JP-A-1-196609 (JP, A) JP-A-6-318102 ( JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G05D 7/06 G05B 11/36 501

Claims (1)

(57) [Claims] 1. A flow rate adjusting means for adjusting a flow rate of a gas,
A flow meter that measures the actual flow rate of the gas, and a flow control valve that controls the flow rate adjusting means based on the output value of the flow meter, in order to compensate for a time delay of a change in the output value of the flow meter ,
1 in which a plurality of first-order lag functions with different time constants are connected in parallel
Using the secondary parallel lag function, when the output value of the flow meter changes
A flow control valve with a delay compensation function, comprising a delay compensation circuit for compensating for an inter-delay .