JPH07106257A - Gas flow rate controller and gas flow rate controlling method using same - Google Patents

Abstract

PURPOSE:To enable controlling gas flow rate while maintaining the constant flow rate ratio of two or more kinds of gas. CONSTITUTION:When SiH4 gas and N2 gas are introduced, while maintaining a constant flow rate ratio, into a treatment equipment with a first MFC(mass flow controller) 31 and a second MFC 32, the flow rate is controlled in the first MFC 31 by comparing a flow rate detection signal A1 obtained by detecting the flow rate of the SiH4 gas with a flow rate setting signal B outputted from a potentiometer 10 for flow rate setting. In the second MFC 32, the flow rate of the N2 gas is controlled by comparing a detection operation signal A'2 calculated on the basis of the flow rate detection signal A1 and a specified flow rate ratio with a flow rate setting signal B2 outputted from a potentiometer 18 for flow rate setting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas flow controller for controlling the flow ratio of each process gas to a constant value when introducing two or more process gases into a processing apparatus. The present invention relates to a gas flow rate control method used.

[0002]

2. Description of the Related Art For example, in the process of manufacturing a semiconductor device, when supplying a process gas into a processing apparatus,
It is necessary that the flow rate of the supplied process gas is always properly controlled. For example, by the CVD method, epitaxial single crystal Si, polycrystalline Si, Si
When forming various thin films of O ₂ , phosphorus glass, Si ₃ N _4, etc., the flow rate of the raw material gas supplied to the processing apparatus determines the characteristics and uniformity of the thin film to be formed.

Therefore, it has been conventionally practiced to use a gas flow rate control device in order to sufficiently control the flow rate of the process gas and then supply the process gas into the processing apparatus. As the gas flow rate control device, for example, a mass flow controller is used. (Mass
Flow Controller, hereinafter referred to as MFC) is used.

The MFC is a gas flow rate control device that captures the flow rate of the process gas by a mass flow rate which is not affected by temperature and pressure. For example, as shown in FIG.
The FC 101 includes a flow rate detection unit 102 that detects the flow rate of the process gas flowing into the FC 101, and a flow rate control unit 103 that controls the flow rate of the gas based on the detection result.

In the flow rate detecting section 102, the MFC
The flow rate of the portion of the process gas flowing into 101 that passes through the detection line 104 is detected. Here, the process gas passing through the detection line 104 and the heating resistors 105, 10 held at a constant temperature are used.
Since heat exchange occurs with each of the heat exchangers 6 and 6, and this appears as a temperature difference between the two that is proportional to the mass flow rate, it can be detected as a voltage signal by the bridge circuit 107. The voltage signal is amplified by the amplifier circuit 108, is displayed on the display 109, and is input to the flow rate control unit 103 as the flow rate detection signal A.

In the flow rate control section 103, the flow rate setting signal B output from the potentiometer 110 for flow rate setting and the flow rate detection signal A are compared by the comparison control circuit 111, which is necessary for equalizing them. Control current I
Are supplied to the thermal valve 112. The thermal valve 112 is, for example, a heater 113.
The valve body 114 is configured to be lowered by supplying an electric current to the valve body 114. Therefore, the comparison control circuit 11
1, the valve body 1
14 moves up and down to open and close the gas flow path.

Each of the circuits described above has a power supply 11
The power supplies 115 supply the necessary electric power.

As described above, in the MFC 101,
By detecting the flow rate of the process gas that has passed through the detection line 104 and comparing this with a set flow rate, flow rate control is performed and a desired flow rate of the process gas can be discharged.

In reality, since two or more kinds of process gases are often introduced into the processing equipment, the respective flow rates are controlled by using the above MFC for each gas species. It will be installed in the processing equipment.

FIG. 5 shows a systematic diagram of a system in which, for example, SiH ₄ gas and N ₂ gas are introduced into the processing apparatus.
The flow paths of the first MFC 131 to the third MFC 133 are connected to the inside of the processing device 135 or the exhaust duct, respectively, and the flow rate of each gas is controlled to flow into the processing device 135 or the exhaust duct. There is.

Specifically, the first MFC 131 and the second MFC 132 control the flow rates of the SiH ₄ gas and the N ₂ gas, respectively, and the flow paths are connected to the inside of the processing device 135 to introduce the gas. You can do it. The flow path of the first MFC 131 is also connected to an exhaust duct so that SiH ₄ gas can flow into the exhaust duct without passing through the processing device 135. The third MFC 134 controls the flow rate of the N ₂ gas, and allows the N ₂ gas to flow into the exhaust duct without passing through the processing device 135.

When the above gas is introduced into the processing device 135, the first MFC 131 and the second MFC 1
By using 32, the SiH ₄ gas and the N ₂ gas are introduced while controlling the flow rates thereof. Similarly, in the exhaust duct SiH
_{When the 4} gas is flowed in, the SiH ₄ gas and the N ₂ gas are introduced while controlling the flow rates by the first MFC 131 and the third MFC 133, respectively.

[0013]

By the way, the above SiH
_{Since the 4} gas has a spontaneous ignition property, when the SiH ₄ gas is introduced into the processing device 135 or the exhaust duct, it is diluted with an inert gas such as the N ₂ gas in advance so that its content is 1% by volume. Must be less than.

For example, S at a flow rate of 100 ml / min
When introducing iH ₄ gas into the exhaust duct, the first MFC
Si controlled to a flow rate of 100 ml / min from 131
The H ₄ gas was allowed to flow out, and the third MFC 133 controlled the flow rate to, for example, 20000 ml / min.
₂ gas outflow, 1st MFC131, 3rd MFC
The flow paths are merged on the downstream side of 133 and mixed gas is introduced. At this time, since the SiH ₄ gas content in the mixed gas is 0.5% by volume, spontaneous ignition does not occur.

[0015] Then, by changing the flow rate of the SiH ₄ gas for various tests, for example when introducing 500 ml / min made flow SiH ₄ gas, SiH ₄ gas 500 ml / min made flow to flow out from the first MFC131 It is assumed that the flow rate of N ₂ gas flowing out from the third MFC 133 is unchanged at a flow rate of 20000 ml / min, while the flow rate is changed to 3. At this time, the first MFC13
1, the mixed gas merged on the downstream side of the third MFC 133 has a SiH ₄ gas content of 2.5% by volume,
If it comes into contact with air, it becomes a dangerous gas that may ignite spontaneously. Therefore, if the flow rate of SiH ₄ gas is increased, it is necessary to increase the flow rate of N ₂ gas in order to dilute it.

[0016] Conversely, for example, if you want the flow rate of SiH ₄ gas and 0 ml / min, since the N ₂ gas is not required for dilution, the flow rate of N ₂ gas also may be 0 ml / min. Here, if the N ₂ gas flowing out from the third MFC 133 is not changed at a flow rate of 20000 ml / min, a large amount of N ₂ gas will be wasted.

As described above, when the flow rate of the SiH ₄ gas is changed, if the flow rate of the N ₂ gas for dilution is also not changed accordingly, the SiH ₄ gas will spontaneously ignite or unnecessary N ₂ gas will not be emitted. Will be leaked in large quantities.

Even when a toxic gas is allowed to flow out, it is necessary to dilute the gas to a permissible concentration or less with a diluting gas as in the case of the SiH ₄ gas.
If the flow rate of the toxic gas is changed, the flow rate of the diluting gas also needs to be changed. Further, even when two or more kinds of gases are flown out while maintaining a constant flow rate ratio, if the flow rate of one gas is changed, it is necessary to change the flow rates of other gases accordingly. .

However, in the system shown in FIG. 5, when the flow rate of a certain gas is changed, in order to keep the flow rate ratio of the remaining gases constant, the flow rates of the other gases are reset. The flow rate must be controlled again. Therefore, for example, when the flow rate of a certain gas fluctuates during the process, the information cannot be reflected in the flow rate control of another gas, and the flow rate ratio also fluctuates.

Therefore, the present invention has been proposed in view of the above conventional circumstances, and when introducing two or more kinds of gases into a processing apparatus, a gas flow rate control apparatus capable of efficiently controlling the flow rate ratio of each gas. The purpose is to provide. Moreover, it aims at providing the gas flow rate control method which can control the flow rate ratio of each gas similarly similarly.

[0021]

The present invention has been proposed to achieve the above object. That is, in a gas flow rate control device for a processing device that uses n kinds of gas (n is an integer of 2 or more) supplied at a predetermined flow rate ratio, a flow rate for detecting the flow rate of the first gas. Detection means and flow rate detection signal A ₁ output from the flow rate detection means
First flow rate control means for controlling the flow rate of the first gas based on the above, and each flow rate of the remaining (n-1) types of gas based on the flow rate detection signal A ₁ and a predetermined flow rate ratio. a detecting arithmetic circuit for calculating the output from the detecting arithmetic circuit (n-1) number of detection calculation signal a _'2 ~A' _n remains based on the (n-1) types of flow individually controllable gas And second to nth flow rate control means.

That is, the gas flow rate control device of the present invention is the first
Although the flow rate detecting means for detecting the flow rate of the gas is included, the flow rate detecting means for detecting the flow rates of the second to nth gases is not included. However, the flow rate control means for each of the second to nth gases calculates the flow rate to be achieved based on the flow rate detection signal A ₁ output from the flow rate detection means for the first gas and a predetermined flow rate ratio. It has a detection calculation circuit, and it is possible to control the flow rates of the second to nth gases by the detection calculation signals A ′ _{2 to} A ′ _n output from this detection calculation circuit.

In the gas flow rate control device of the present invention, the flow rate detection signal A ₁ or the (n-1) number of detection calculation signals A ′ ₂ to
A 'and _n, first to n first through n comparison control circuit of the n-number of the flow rate setting signal B ₁ .about.B _n outputted from the flow rate setting means for determining a control amount by comparing discrete May be provided respectively.

In this case, the flow rate control of the first gas is performed by the flow rate detection signal A ₁ output from the flow rate detection means and the flow rate setting signal B ₁ output from the first flow rate setting means, and the second flow rate control is performed. Through the flow rate control of the nth gas, the (n-1) number of detection calculation signals A ′ ₂ calculated in the detection calculation circuit based on the flow rate detection signal A ₁ and a predetermined flow rate ratio.
Performing A 'and _n, the n number of the flow rate setting signal B ₁ .about.B _n output from the flow rate setting means of the second to n.

Alternatively, in the gas flow rate control device of the present invention, the first flow rate control means is set to the flow rate detection signal A ₁
And the flow rate setting signal B ₁ output from the first flow rate setting means
And a first comparison control circuit for determining a control amount by comparing
Wherein the (n-1) and the detection calculation signal A _'2 ~A' _n, the flow rate setting signal B ₁ and calculated on the basis of the predetermined flow rate ratio (n-1) number of setting operation signal B ' ₂ .about.B _'n and may be used as one with each comparison control circuit of the second to n for determining a control amount compared separately.

In this case, the flow rate control of the second to nth gases is performed by individually calculating each flow rate of the gas based on the flow rate detection signal A ₁ and a predetermined flow rate ratio, and the detection calculation signals A ′ _{2 to} A ′. 'in addition to the detection calculation circuit for outputting a _n, setting operation signal B each flow rate of the gas is calculated separately on the basis of the flow rate setting signal B ₁ and a predetermined flow ratio' setting for outputting the ₂ .about.B _'n It will be performed using an arithmetic circuit. Then, the detection calculation signals A ′ _{2 to} A ′ _n output from the detection calculation circuit and the setting calculation signals B ′ _{2 to} B ′ _n output from the setting calculation circuit are sent to the second to nth comparison control circuits. And individually comparing them, the second to nth
The gas flow rate may be controlled.

In the above gas flow rate control device, the mass flow rate is measured as the flow rate.

The gas flow rate control method according to the present invention uses the gas flow rate control device as described above, and the flow rate ratio of n kinds of gas (where n is an integer of 2 or more) is always constant. It is introduced into the processing apparatus while maintaining the above.

[0029]

The gas flow rate control device of the present invention does not have flow rate detection means for detecting the flow rates of the second to nth gases. However, the flow rate control means for each of the second to nth gases are the same as those for the first
Flow rate detection signal A ₁ output from the gas flow rate detection means
And a predetermined flow rate ratio, the detection calculation circuit calculates a flow rate to flow out, and each detection calculation circuit outputs the detection calculation signals A ′ _{2 to} A ′ _n, thereby the second to nth It is possible to control the flow rate of the gas.

For example, each of the first to nth flow rate control means is provided with a flow rate setting means and a comparison control circuit, so that the flow rate detection signal A ₁ or the detection calculation signals A ′ _{2 to} A ′ _n , The control amount can be determined by individually comparing the flow rate setting signals B _{1 to} B _n output from each flow rate setting means.

Alternatively, in the second to nth flow rate control means, the flow rate setting signal B output from the first flow rate setting means
A setting calculation circuit for calculating the flow rate to be achieved based on ₁ and a predetermined flow rate ratio, and a comparison control circuit are provided, so that the detection calculation signals A ′ _{2 to} A ′ _n and the setting flow rate are calculated. set output from the arithmetic circuit calculating the signal B _'2 ~B' _n
And can be compared individually to determine the controlled variable.

By using the gas flow rate control device as described above, it becomes possible to introduce two or more kinds of gas into the processing device while keeping the flow rate ratios constant. Further, even when the flow rate of the first gas fluctuates, the information is reflected in the flow rate control means of the second to nth gases, so that a constant flow rate ratio can always be maintained.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described below with reference to the drawings. In the present embodiment, the gas flow rate control device according to the present invention is used in a processing device for semiconductor manufacturing (for example, a CVD device, a dry etching device, etc.) so as to maintain a constant flow rate ratio of two or more process gases. It was used to control the flow rate.

As shown in FIG. 1, the outline of the system of the gas flow rate control device according to this embodiment is, for example, the first MFC.
The gas flow rates of the conventional gas flow rates shown in FIG. 5 are that the flow paths of the third to third MFCs 33 are connected to the inside of the processing device 35 or to the exhaust duct, respectively, and the flow rate of each gas is controlled. It is similar to the control device. However, in the gas flow rate control device according to the present embodiment, the first MFC 31 to the third MFC 33 are not independent of each other, and for example, the second MFC 32 connected to the processing device 35 is also connected to the processing device 35. A flow rate detection signal A ₁ detected by the first MFC 31 and a detection calculation signal A ′ ₂ calculated based on a predetermined flow rate ratio are supplied.

Example 1 In the gas flow rate control device of this example, the first MFC 3
The first, second MFC 32, and third MFC 33 are, for example,
SiH ₄ gas introduced into the processing apparatus 35 or the exhaust duct, the N ₂ gas is introduced into the processing apparatus 35, is a flow rate control of the N ₂ gas is introduced into the exhaust duct performs respectively.

[0036] Then, the first connected to the processing unit 35 MFC31, the flow control of the second MFC32, the flow rate detection signal A ₁ or detection calculation signal A _'2, a first flow rate setting means or the second The flow rate setting signals B ₁ and B ₂ output from the flow rate setting means are individually compared and performed. Also, the first MFC 31 and the third MFC 3 connected to the exhaust duct
The flow rate control of No. 3 is individually compared with the flow rate detection signal A ₁ or the detection calculation signal A ′ ₃ and the flow rate setting signals B ₁ and B ₃ output from the first flow rate setting means or the third flow rate setting means. Then do.

Specifically, for example, as shown in FIG. 2, a first MF including a flow rate detector 2 and a flow rate controller 3 is provided.
C31, a second MFC 32 that does not have the flow rate detection unit 2 and is composed only of the flow rate control unit 3 ′, and a third MFC 33 (not shown) that does not have the flow rate detection unit 2 either.

The flow rate detection unit 2 in the first MFC 31 detects the flow rate of the SiH ₄ gas passing through the detection line 4. Here, the above-mentioned detection line 4
Heat exchange occurs between the SiH ₄ gas passing through the inside and the heating resistors 5 and 6 held at a constant temperature,
Since this appears as a temperature difference between the two that is proportional to the mass flow rate, it can be detected as a voltage signal by the bridge circuit 7. The voltage signal is amplified by the amplifier circuit 8, is displayed on the display 9, and is input to the flow rate control unit 3 as the flow rate detection signal A ₁ .

The flow rate control unit 3 in the first MFC 31 compares the flow rate setting signal B ₁ output from the flow rate setting potentiometer 10 with the flow rate detection signal A ₁ in the comparison control circuit 11, and compares them. The control current I ₁ required to make them equal is supplied to the thermal valve 12. The thermal valve 12 is configured such that the valve body 14 is lowered by supplying a current to the heater 13, for example. Therefore, the comparison control circuit 11
Along with the change of the control current I ₁ sent from the valve body 1,
4 moves up and down to open and close the gas flow path.

Each of the circuits described above has a power supply 15
And the necessary power is supplied from the power supply 15.

As described above, in the first MFC 31, the flow rate detection signal A ₁ obtained by detecting the flow rate of the SiH ₄ gas that has passed through the detection line 4 is compared with the flow rate setting signal B ₁ . Flow rate is controlled and SiH of desired flow rate
It is designed so that ₄ gases can be discharged.

On the other hand, a second M for controlling the flow rate of N ₂ gas
The FC 32 does not have the flow rate detection unit 2 but has a detection calculation circuit 16 in the flow rate control unit 3 ′. The detection calculation circuit 16 uses the second MFC 31 based on the flow rate detection signal A ₁ generated in the first MFC 31 and a predetermined flow rate ratio.
The flow rate to be flown out in the FC 32 is calculated and displayed on the display unit 17 as the detection calculation signal A ′ _{2 and} output to the comparison control circuit 19. Then, in the comparison control circuit 19, the detection calculation signal A ′ ₂ is compared with the flow rate setting signal B ₂ output from the flow rate setting potentiometer 18,
The control current I ₂ necessary for equalizing the _two is supplied to the thermal valve 20 to open / close the gas flow path.

As described above, in the second MFC 32, the N ₂ gas having a desired flow rate ratio to the flow rate of the SiH ₄ gas can be introduced into the processing apparatus 35 without detecting the flow rate. it can. Therefore, the first MFC 31 and the second MFC 32 cause SiH ₄ to enter the processing device 35.
When introducing the gas and the N ₂ gas, a mixed gas having a constant flow rate ratio can be introduced.

Further, the first MFC 31 and the third MFC 3
In the case where SiH ₄ gas and N ₂ gas are introduced into the exhaust duct by the method 3 as well, they are similar to the case where they are introduced into the processing device 35. That is, although not shown, the third MFC 33 has the same configuration as the second MFC 32, and the first MFC 31
In the comparison control circuit, the detection calculation signal A ′ ₃ calculated based on the flow rate detection signal A ₁ generated in step ₁ and a predetermined flow rate ratio, and the flow rate setting signal B ₃ output from the potentiometer for flow rate setting. As a result of comparison, the flow rate is controlled by supplying the control current I ₃ required for equalizing the two to the thermal valve. At this time, the flow path of the first MFC 31 is naturally connected to the exhaust duct side.

Therefore, the first MFC 31 and the third MFC
By the FC 33, even when introducing SiH ₄ gas and N ₂ gas into the exhaust duct, it is possible to introduce a mixed gas having a constant flow rate ratio.

[0046] By using the gas flow control device as described above, it is possible to the flow ratio of N ₂ gas to SiH ₄ gas to a predetermined flow rate ratio, also, SiH ₄
Even when the gas flow rate changes, the information is reflected in the N ₂ gas flow rate control means, so that a constant flow rate ratio can always be maintained. Therefore, the concentration of SiH ₄ gas can be kept within the safe permissible concentration, and spontaneous ignition does not occur. Also, the second MFC 32 and the third MFC
By simplifying the configuration of (1), the system of the gas flow rate control device can be downsized as compared with the conventional system.

Embodiment 2 In this embodiment, in the system shown in FIG. 1, the first MFC 31 and the second MF connected to the processing device 35.
C32 flow control, the flow rate detection signal A ₁ or detection calculation signal A _'2, on the basis of the first flow rate setting signal B ₁ or the flow rate setting signal B ₁ is outputted from the flow rate setting means and a predetermined flow rate ratio The calculation is performed by individually comparing with the calculated B ′ ₂ .
Also, the first MFC 31, the third connected to the exhaust duct
Based of the flow control MFC33, the flow rate detection signal A ₁ or detection calculation signal A _'3, the first flow rate setting signal B ₁ or the flow rate setting signal B ₁ is outputted from the flow rate setting means and a predetermined flow rate ratio It is performed by individually comparing with B ′ ₃ calculated as above.

The gas flow rate control device of this embodiment has the first M
FC31, 2nd MFC32, 3rd MFC33 are respectively introduced into the processing unit 35 or the exhaust duct SiH ₄
Gas, N ₂ gas introduced into the processing apparatus 35, that control the flow rate of N ₂ gas introduced into the exhaust duct, as shown in FIG. 3, the first MFC31 flow rate detector 2 and the flow control unit 3 and has a second MFC 32 and a third MFC 33
(Not shown) does not have the flow rate detection unit 2, and the flow rate control unit 3 '
It is similar to the first embodiment in that it is composed of only.

The structure of the first MFC 31 is as follows.
This is exactly the same as the first MFC 31 shown in the first embodiment. That is, in the first MFC 31, by comparing the flow rate detection signal A ₁ obtained by detecting the flow rate of the SiH ₄ gas passing through the detection line 4 with the flow rate setting signal B ₁ ,
The flow rate is controlled so that a desired flow rate of SiH ₄ gas can be flown out.

On the other hand, the second MFC 32 has a setting calculation circuit 21 in addition to the detection calculation circuit 16 in the flow rate control section 3 '.
Is different from the first embodiment. Detection arithmetic circuit 16
Calculates the flow rate that should flow out in the second MFC 32 based on the flow rate detection signal A ₁ generated in the first MFC 31 and a predetermined flow rate ratio, and displays it on the display 17 as a detection calculation signal A ′ _2. The comparison control circuit 19
Output to. Further, the setting arithmetic circuit 21 uses the second MF based on the flow rate setting signal B ₁ generated by the potentiometer 10 of the first MFC 31 and a predetermined flow rate ratio.
Calculating the flow rate to be achieved in the C32, and outputs it to the comparison control circuit 19 as the set operation signal B _'2.

[0051] In the comparison control circuit 19, the detection operation signal A _'2 is the set operation signal B' is compared to _2, the control necessary to equalize both current I ₂ Thermal valve 2
0 to open and close the gas flow path.

As described above, in the second MFC 32, N ₂ gas having a desired flow rate ratio with respect to the flow rate of SiH ₄ gas can be introduced into the processing apparatus 35 without detecting the flow rate. it can. Therefore, the first MFC 31 and the second MFC 32 cause SiH ₄ to enter the processing device 35.
When introducing the gas and the N ₂ gas, a mixed gas having a constant flow rate ratio can be introduced.

Further, the first MFC 31 and the third MFC 3
In the case where SiH ₄ gas and N ₂ gas are introduced into the exhaust duct by the method 3 as well, they are similar to the case where they are introduced into the processing device 35. That is, the detection calculation signal A ′ ₃ calculated based on the flow rate detection signal A ₁ generated in the first MFC 31 and the predetermined flow rate ratio, and the flow rate setting signal B ₁ and the predetermined flow rate ratio. By the comparison with the set calculation signal B ′ ₃ thus set, the control current I ₃ necessary for equalizing the two is supplied to the thermal valve to open / close the gas flow path.

At this time, the flow path of the first MFC 31 is naturally connected to the exhaust duct side.

Therefore, the first MFC 31 and the third MFC
By the FC 33, even when introducing SiH ₄ gas and N ₂ gas into the exhaust duct, it is possible to introduce a mixed gas having a constant flow rate ratio.

[0056] By using the gas flow control device as described above, it is possible to the flow ratio of N ₂ gas to SiH ₄ gas to a predetermined flow rate ratio, also, SiH ₄
Even when the gas flow rate changes, the information is reflected in the N ₂ gas flow rate control means, so that a constant flow rate ratio can always be maintained. Therefore, the concentration of SiH ₄ gas can be kept within the safe permissible concentration, and spontaneous ignition does not occur. Also, the second MFC 32 and the third MFC
By simplifying the configuration of (1), the system of the gas flow rate control device can be downsized as compared with the conventional system.

In the above-described embodiment, an example in which the SiH ₄ gas and the N ₂ gas are introduced into the processing device 35 and the exhaust duct has been described, but the introduced gas is not limited to the above. For example, a toxic gas such as PH ₃ gas or B ₂ H ₆ gas may be used at a certain safe allowable concentration (for example, PH ₃
The gas flow rate control device of the present invention is also effective when gas is introduced while maintaining 0.5 ppm or less). In this case, the flow rates of the PH ₃ gas and the B ₂ H ₆ gas are controlled by the first MFC, and the introduction of the diluting gas and other necessary gases is controlled by the 2nd to nth MFCs. In the second to nth MFCs, the flow rate control is performed by calculating the flow rate of the diluting gas or other necessary gas to be introduced based on the flow rate detection signal output from the first MFC and a predetermined flow rate ratio. I do. As a result, PH ₃ gas and B ₂ H ₆ gas always flow out at a constant flow rate ratio, ensuring safety.

Furthermore, even if the gas introduced into the processing device or the exhaust duct is a gas that is not pyrophoric or toxic,
The gas flow rate control device of the present invention is suitable for introducing a gas of at least one type into a processing device or an exhaust duct while maintaining a constant mixing ratio.

[0059]

As is apparent from the above description, by using the gas flow rate control device according to the present invention, the flow rate ratio of two or more kinds of gases can be set to a predetermined flow rate ratio. Even when the flow rate of gas changes, the information is reflected in the flow rate control means of other gas, so that it is possible to always maintain a constant flow rate ratio.

Therefore, the gas flow rate control method ensures the safety even when introducing the gas having spontaneous combustion and toxicity. Further, since the second to n-th MFCs do not require a flow rate detection unit, the configuration thereof is simplified, and the system of the gas flow rate control device can be downsized as compared with the conventional system.

That is, the gas flow rate control method according to the present invention is
The method is efficient and highly reliable as a method of introducing two or more kinds of gases while maintaining a predetermined flow rate ratio.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an outline of a system of a gas flow rate control device according to an embodiment.

FIG. 2 is a configuration diagram schematically showing a main part of a gas flow rate control device according to an embodiment.

FIG. 3 is a configuration diagram schematically showing a main part of a gas flow rate control device according to another embodiment.

FIG. 4 is a configuration diagram schematically showing a main part of a gas flow rate control device according to a conventional example.

FIG. 5 is a schematic diagram showing an outline of a system of a gas flow rate control device according to a conventional example.

[Explanation of symbols]

2 ... Flow rate detection unit 3 ... Flow rate control unit 4 ... Detection line 5, 6 ... Heating resistor 7 ... Bridge circuit 8 ... Amplification circuit 9, 17 ... Indicator 10,18 ... potentiometer 11, 19 ... comparison control circuit 12, 20 ... thermal valve 13 ... heater 14 ... valve body A ₁ ... flow rate detection signal A _'2, A' ₃・ ・ ・ Detection calculation signal B _{1 to} B ₃・ ・ ・ Flow rate setting signal B ′ ₂ , B ′ ₃・ ・ ・ Setting calculation signal

Claims (5)

[Claims] 1. A gas flow controller for a processing apparatus using n kinds of gases (n is an integer of 2 or more) supplied at a predetermined flow rate ratio, wherein the flow rate of the first gas is Based on the flow rate detection means for detecting, the first flow rate control means for controlling the flow rate of the first gas based on the flow rate detection signal output from the flow rate detection means, and based on the flow rate detection signal and a predetermined flow rate ratio. Remain (n
-1) A detection arithmetic circuit that individually calculates the flow rate of each type of gas, and the remaining (n-1) types of gas based on the (n-1) number of detection arithmetic signals output from the detection arithmetic circuit. A gas flow rate control device comprising second to nth flow rate control means for individually controlling the flow rate. 2. The first to nth flow rate control means,
A first control amount is determined by individually comparing the flow rate detection signal or the (n-1) detection calculation signals and n flow rate setting signals output from the first to nth flow rate setting means. 2. The gas flow rate control device according to claim 1, further comprising first to nth comparison control circuits. 3. The first flow rate control means comprises a first comparison control circuit for comparing the flow rate detection signal with a flow rate setting signal output from the first flow rate setting means to determine a control amount. The second to nth flow rate control means are the same as the (n-1)
The second to n-th to determine the control amount by individually comparing the individual detection calculation signals with the (n-1) setting calculation signals calculated based on the flow rate setting signal and the predetermined flow rate ratio. 2. The gas flow rate control device according to claim 1, wherein each of the comparison control circuits is provided. 4. The gas flow rate control device according to claim 1, wherein the flow rate is a mass flow rate. 5. The gas flow rate control device according to any one of claims 1 to 4, wherein n types of gas (where n is an integer of 2 or more) are always kept in a flow rate ratio to each other. A method for controlling gas flow rate, characterized in that the gas is introduced into the processing apparatus while being kept constant.