JPH07306720A - Method and device for producing mixed gas of specific concentration - Google Patents

Abstract

PURPOSE:To obtain the device and method which mixes >=2 kinds of gas at a specific ratio from cylinders which are filled with them independently by controlling the gas flow rate of a 2nd liquid on the basis of the flow rate of a 1st liquid in real time. CONSTITUTION:This device has a 1st flow passage l where the 1st liquid flows, a 2nd flow passage 2 where the 2nd liquid flows, a means 6 which detects the gas flow rate of the 1st liquid, a means which generates a signal based upon the flow rate of the 1st liquid, and a means which controls the gas flow rate of the 2nd liquid by the signal from the above means in real time. The two liquids are mixed at the specific ratio while the flow rate of the 2nd liquid is controlled according to y=aX<b>+c. In the equation, X is the flow rate of the 1st liquid, (y) is the flow rate of the 2nd liquid, and (a), (b), and (c) vary with the ratio of the 1st liquid to the 2nd liquid, but are experimentally found constants at the certain ratio of the two liquids. Consequently, the mixed gas of invariably constant concentration can be produced following up the demanded flow rate at a use point.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an apparatus and method for mixing two or more gases to a given concentration.

[0002]

BACKGROUND OF THE INVENTION In the semiconductor industry, SiH ₄ , PH ₃
And other special material gases are used. These SiH
₄ , PH ₃ gas is usually diluted with a balance gas such as H ₂ , N ₂ , He, Ar, etc. and filled in a cylinder container for use. In this case, in order to keep the supply quality of the obtained semiconductor constant without changing the conditions of the manufacturing process, the fluctuation of the mixing ratio of the two gases must be suppressed to 0 or within the minimum allowable range at a predetermined concentration. . For example H
When an attempt is made to obtain a mixed gas containing PH ₃ 1 parts by volume with respect to ₂ 10 parts by volume, always PH _3: H ₂ is 10: 1 is that it must be mixed with (volume basis).

Conventionally, for example, a dopant such as PH ₃ and H ₂
Was mixed in a device as shown in FIG. However, the conventional method cannot always obtain a mixed gas of a dopant gas and a diluent gas having a constant concentration. For example, even if an attempt is made to obtain a mixture of 1 liter of the dopant gas with respect to 10 liters of the diluent gas, the mixture having a volume ratio of 10: 1 is not always obtained.

Therefore, conventionally, semiconductors have been manufactured by using a cylinder filled with a gas mixture having a predetermined ratio in advance. However, in this case, a plurality of mixed gas cylinders had to be prepared in order to obtain mixed gas of various ratios of the dopant gas and the diluent gas. In addition, since the cylinder must be changed relatively frequently in order to use the mixed gas, the fluctuation of the mixed gas concentration occurs within ± 5% of the relative concentration each time the cylinder container is replaced. It was

[0005]

SUMMARY OF THE INVENTION The present invention is directed to an apparatus and method for mixing two or more gases, each of which is individually filled, in a predetermined ratio.

The present invention is a device for mixing a second fluid with a first fluid at a predetermined ratio, and a first fluid through which the first fluid flows.
A flow path, a second flow path through which the second fluid flows, a means for detecting the gas flow rate of the first fluid, a means for generating a signal based on the flow rate of the first fluid, and a gas flow rate of the second fluid by a signal from the means The flow rate of the second fluid is y = ax ^b + c including a control means for controlling in real time, where x is the flow rate of the first fluid, y is the flow rate of the second fluid, and a
And b and c vary with the ratio of the second fluid to the first fluid, but for a given ratio of the two fluids, the two fluids controlled according to Regarding a mixing device.

Further, the present invention is a method of mixing a second fluid with a first fluid at a predetermined ratio, by detecting a gas flow rate of the first fluid and using a signal based on the flow rate of the first fluid, an equation y = ax ^b + C (where x is the flow rate of the first fluid, y is the flow rate of the second fluid, a
And b and c change depending on the ratio of the second fluid to the first fluid, but are constants experimentally obtained at a constant ratio of the two fluids), and the gas flow rate of the second fluid is calculated in real time. The present invention relates to a method of mixing a first fluid and a second fluid in a predetermined ratio, which is characterized by controlling.

The present invention will be described with reference to the drawings. In FIG. 2, a diluting gas such as H ₂ and He is caused to flow from the first flow passage, a dopant gas such as SiH ₄ and PH _{3 is} caused to flow from the second flow passage, and y = ax ^b + c (equation Where x is the flow rate of the first fluid, y is the flow rate of the second fluid, and a
And b and c vary according to the ratio of the second fluid to the first fluid, which is an experimentally determined constant for a constant ratio of the two fluids) to control the dopant gas flow rate in real time.

For example, when one wants to obtain a mixture in which the diluent gas is H ₂ and the dopant gas is PH ₃ and the Dopane gas concentration is 10%, for example, a =
It becomes 0.992 and b = 0.995. When the concentration becomes 20%, for example, a = 0.823, b = 0.854, c = 0
Becomes Since this data changes little by little as time passes, it is preferable to perform the zero point check every 1 to 2 hours. The zero point check is a signal from the means for stopping the supply of gas and generating a signal based on the flow rate of the first fluid,
The above a and / or b and / or c is corrected.

A more detailed description will be given with reference to FIG. 1
Is the first flow path for the diluent gas, 2 is the second flow path for the dopant gas
Flow path, 3 valves, 4 filters, 5 valves, 6 MFM
(Mass flow meter), 7 is a valve, 8 is a valve, 9 is a filter, 10 is a valve, 11 is a mass flow controller, 12 is a valve, 13 is a purge gas valve, 14 is a pressure gauge for measuring internal pressure, and 15 is a buffer tank. , 16 are electronic pressure regulators for adjusting the pressure of the mixed gas.

The dilution gas passes through the valve 3, the filter 4 and the valve 5, and the flow rate is measured by the MFM 7. On the other hand, the flow rate of the dopant gas is controlled by the MFC 11 through the valve 8, the filter 9 and the valve 10. These diluent gas and dopant gas pass through the valve 11 and the valve 12, respectively, are mixed and stirred at the confluence of the valves, and are introduced into the buffer tank.
In this case, the flow rate in the MFM 12 of the dilution gas line is input as an output voltage to the arithmetic circuit, the MFC of the dopant gas line calculates a voltage corresponding to the flow rate to be added, and the voltage is input to the MFC. With this control method, it is possible to constantly generate a mixed gas of a constant concentration by following the demand flow rate at the use point (semiconductor manufacturing apparatus side). The pressure of the mixed gas from the buffer tank 15 is adjusted by the electronic pressure regulator 16, and the mixed gas is sent to the use point through the valve 17. When the apparatus is stopped, a purge gas is introduced to expel the dopant gas remaining in the system.

The present invention also includes a mode in which two or more kinds of gases are mixed with one kind of gas. This becomes the mode shown in FIG. The device shown in FIG.
Gas B and gas C are mixed uniformly. In this case, the relationship between the gas A and the gas B is expressed by the following equation: y = ax ^b + c (where x is the flow rate of the gas A, y is the flow rate of the gas B, and a, b and c are changed depending on the ratio of the gas B and the gas A). But 2
It is an experimentally determined constant for a given ratio of two fluids). Further, the relationship between the gas A and the gas C is expressed by the following equation: y '= a'xb' + ^c '(where x is the flow rate of the gas A, y'is the flow rate of the gas C, a'
And b'and c'depend on the ratio of gas C to gas A, but for a given ratio of the two fluids are experimentally determined constants).

No matter how many kinds of gases should be mixed with the first fluid (gas A), the same system as the gas C shown in FIG. 3 may be connected to the first flow path 1. 2 in FIG.
8 is a valve, 29 is a filter, 30 is a valve, 31 is an MFC for gas C, 27 is a valve, and 33 is a purge gas valve for gas C.

The device shown in FIG. 2 has a dopant gas (S
Examples of iH ₄ ) and diluent gas (He) have been shown, but the type of gas does not matter in the present invention.

When the use at the point of use is stopped, the internal pressure of the pipe reaches the upper limit value or the flow rate of the first flow path reaches the lower limit value, at which time the supply of both gases is stopped. When the use of the use point is started, the internal pressure of the pipe reaches the lower limit value, and then supply of both gases is started.

By connecting the reference concentration analyzer every certain period (for example, once a year), the output values of the two flow rate control devices are read and the above a, b and c are calibrated.

Examples of the present invention will be described below. However, this is one example of the content of the invention, and the present invention is not limited to this content.

Example 1 In this example, the flow rate reading of the MFM was carried out in a mixing apparatus of a proportional flow rate control system (a method of controlling the flow rate so that the concentration of MFC of the component gas becomes constant with respect to the MFM flow rate of the diluent gas). This is an example in which the correlation between the flow rate setting value of MFC and the flow rate setting value of MFC was clarified, and the concentration was confirmed to be constant when proportional control was performed using the relational expression.

He as a dilution gas and Si as a component gas
Use H ₄ and adjust the He gas supply pressure to regulator RV
-2 was adjusted to 3.5 kg / cm ² G, and the SiH ₄ gas supply pressure was adjusted to 4 kg / cm ² G with RV-1. The system flow is shown in FIG.

An ultrasonic wave transmission type mixed gas concentration meter was used as an analyzer. Also, the analyzer is always 500c by MFC-2.
It was adjusted so that the mixed gas at a flow rate of c / min was sampled. The mixed gas generation flow rate is set to 0 by MFC-3.
Adjustment was performed at a pitch of 500 cc / min in the range of 7 l / min.

The SiH ₄ gas addition flow rate was adjusted by MFC-1 so that a predetermined generation concentration (20%) was obtained for each mixed gas generation flow rate. The He gas flow rate reading (X) and the SiH ₄ gas flow rate set value (Y) when the generated concentration coincided with the predetermined generated concentration were regressed by the least-multiplication method. Regressed by the number method regression to ^{(Y = ax b + c)} . As a result of regression, a correlation of Y = 0.982 ^{× −0.968} was obtained.

The generated concentration was compared between the method of proportional control using the power number obtained by the above method and the conventional method of proportional control according to the set value of the flow rate.

The flow rate is set to 0 to 7 by the MFC-3 on the rear stage side.
Generated concentration when changing to 1 / min (see Fig. 5)
It has been confirmed that is proportional to the flow rate change in proportional control using a power.

When the concentrations were 10%, 30% and 40%, the generated concentration was confirmed by the same method. FIG. 6 shows the relationship between the flow rate and the generated concentration at each concentration.

Example 2 The flow of the mixing apparatus for automatic operation is shown in FIG.

Automatic operation means that when the use of the mixed gas is stopped at the point of use, the flow rate instruction value of the MFM is 3
When it becomes less than 00cc / min, the pneumatic valve AV-3,
Close 4, 5 and 6 to stop the supply of the mixed gas. Also, when the mixed gas is started to be used at the point of use, the pressure sensor (P) detects that the internal pressure of the pipe has dropped, and when the indicated value becomes less than 3.3 kg / cm ² G. Pneumatic valves AV-3, 4, 5 and 6 are opened to start supply. The supply pressure of the mixed gas was set to 3 kg / cm ² G by an auto pressure regulator (UR), and the generated concentration set value was set to 20%.

He was used as a dilution gas and the supply pressure was set to 3.
It was adjusted to 5kg / cm ² G, to adjust the supply pressure using SiH ₄ as a component gas to 4.0kg / cm ² G.

An MFC is installed at the outlet of the apparatus to simulate the flow rate fluctuation at the point of use, and the mixed gas generation flow rate of the mixing apparatus is changed to 7 → 5 → 3 → 1 → 0.5 → 0 → 0.5.
→ 1 → 3 → 5 → 7 l / min. It was confirmed that the generated concentration was constant regardless of the change in flow rate. (See Figure 8).

Example 3 MFM and MFC when obtaining the power relation in Example 1
The zero point output (output voltage in the state where there is no gas flow) is set to 0 mV.

The output at the zero point at this time is set as a reference voltage,
When the voltage value changes with time and the output voltage of the MFM becomes emV and the output voltage of the MFC becomes dmV in a state where there is no gas flow, the calculation formula of Y = ax ^b , which is the original exponent, is Y Rewrite as −d = a (x−e) ^b to make a new arithmetic expression and calibrate the zero point.

Y = ax ^b + c → Y = ax ^b + c ′ Using the conventional method and the control by the above-mentioned method, the time-dependent change in the generated concentration was confirmed.

As a confirmation method, He was used as a diluting gas and SiH ₄ was used as a component gas, the generation concentration was set to 20%, and the generation flow rate was adjusted to 3 l / min.

When the density of generation was confirmed every two months for 12 months, a deviation of 1.2% was generated even if the density of generation was set to 20% if the zero point was not calibrated. did. However, with the control method by rewriting the arithmetic expression calibrating the zero point with the change of the zero point, the generated concentration during this period did not change. (See Figure 9)

[Brief description of drawings]

FIG. 1 is a schematic view of a conventional two-gas mixing device.

FIG. 2 is a schematic view of the mixing apparatus of the present invention.

FIG. 3 is a schematic view of a mixing apparatus according to another aspect of the present invention.

FIG. 4 is a schematic diagram of a system flow for carrying out the first embodiment.

FIG. 5 is a graph showing the relationship between flow rate and generated concentration.

FIG. 6 is a graph showing the relationship between flow rate and generated concentration at various concentrations.

FIG. 7 is a schematic view of an apparatus for automatic driving according to the present invention.

FIG. 8 is a graph showing the relationship between time, flow rate, and generated concentration.

FIG. 9 is a graph showing the relationship between time and generated concentration.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiko Kurushima 75-1 Shingo, Higashimatsuyama City, Saitama Prefecture, Osaka Oxygen Industry Co., Ltd. (72) Inventor Shigeki Hayashi 75-1 Shingo, Higashimatsuyama City, Saitama Prefecture Osaka Oxygen Industry Co., Ltd. In the development center

Claims (7)

[Claims] 1. A device for mixing a second fluid with a first fluid at a predetermined ratio, wherein a first flow path through which the first fluid flows, a second flow path through which the second fluid flows, and a first fluid The flow rate of the second fluid is y = ax, including a means for detecting the gas flow rate, a means for generating a signal based on the flow rate of the first fluid, and a control means for controlling the gas flow rate of the second fluid in real time by the signal from the means. ^b + c (where x is the flow rate of the first fluid, y is the flow rate of the second fluid, a
And b and c vary with the ratio of the second fluid to the first fluid, but for a given ratio of the two fluids are experimentally determined constants) 2
A device that mixes two fluids at a specified ratio. 2. When the internal pressure of the pipe reaches the upper limit or when the flow rate of the first flow path reaches the lower limit, the supply of both gases is stopped, and when the internal pressure of the pipe reaches the lower limit, both The apparatus according to claim 1, wherein the supply of gas is started. 3. The apparatus according to claim 1, wherein said a and / or b and / or c is calibrated by a signal from a means for generating a signal based on the flow rate of the first fluid when the supply of gas is stopped. . 4. The method according to claim 1, wherein the output values of the two flow rate control devices are read by connecting the reference concentration analyzer at every certain period to calibrate the a and / or b and / or c. apparatus. 5. A method of mixing a second fluid with a first fluid at a predetermined ratio, wherein the gas flow rate of the first fluid is detected,
A signal based on the flow rate of the first fluid yields the equation y = ax ^b + c, where x is the flow rate of the first fluid, y is the flow rate of the second fluid, and a and b and c are the ratio of the second fluid to the first fluid. However, the constant flow rate of the two fluids is a constant obtained experimentally), and the gas flow rate of the second fluid is controlled in real time.
A method of mixing a fluid and a second fluid in a predetermined ratio. 6. A method of mixing two or more kinds of second fluids with a first fluid at a predetermined ratio, wherein a gas flow rate of the first fluid is detected, and a signal based on the flow rate of the first fluid is detected.
Sending to respective means for controlling the flow rate of the second fluid,
For each fluid, wherein ^{y = ax b + c, y} '= a'x b' + c'─── ( wherein x is the first fluid flow, y, Y'── the respective second fluid flow, a , A '-and b, b'-and c,
c '-varies depending on the ratio of each of the second fluids to the first fluid, but at a constant ratio of the two fluids, it is an experimentally determined constant). Is controlled in real time, and the first fluid and the second fluid are mixed at a predetermined ratio. 7. An apparatus for mixing two or more kinds of second fluids at a predetermined ratio with respect to a first fluid, wherein a first flow path through which the first fluid flows, and a plurality of second fluids through which each flows. Two flow paths, means for detecting the gas flow rate of the first fluid, means for generating a signal based on the flow rate of the first fluid, and control means for controlling the gas flow rate of each of the plurality of second fluids in real time by the signal from the means. And the flow rate of each second fluid is y = ax ^b + c, y ′ = a′x ^b ′ + ^c ′ ── (where x is the flow rate of the first fluid, y and y ′ ─ are the respective second fluids) Flow rate, a, a '-and b, b'-and c,
c '-varies depending on the ratio of each of the second fluids to the first fluid, but for a given ratio of the two fluids is a constant determined experimentally)
Device for mixing fluid and second fluid at a predetermined ratio