JP2776441B2 - Process gas supply device and supply method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a process gas supply device for a process of forming various thin films and a dry etching process of a fine pattern, and particularly to a desired balance gas which enables high quality film formation and high quality etching. The present invention relates to an apparatus and a method for supplying a process gas to a process apparatus by mixing the raw material gas with a desired raw material gas concentration in situ.

BACKGROUND ART In recent years, in processes such as formation of high-quality thin films and dry etching of fine patterns, the technology of ultra-cleaning a process atmosphere, that is, a technology of supplying an ultra-high-purity gas to a process apparatus has become very important.

For example, in the case of semiconductor devices, the size of unit elements is decreasing year by year in order to improve the degree of integration of integrated circuits, and semiconductor devices having a size of 1 μm to submicron or even 0.5 μm or less are practically used. It is actively researched and developed for realization. The manufacture of such a semiconductor device is performed by repeatedly forming thin films or etching these thin films into a predetermined circuit pattern. Such a process is usually performed in a reduced-pressure atmosphere in which a silicon wafer is placed in a process chamber and a predetermined gas is introduced. The purpose of reducing the pressure is to increase the mean free path of gas molecules for etching and filling of through holes and contact holes having a high aspect ratio, and to control the gas phase reaction.

If impurities are mixed in the reaction atmosphere of these processes, problems such as deterioration of film quality of the thin film, inability to obtain etching processing accuracy, deterioration of selectivity, and insufficient adhesion between the thin films are caused. Is generated. In order to produce submicron and lower submicron integrated circuits on a large-diameter wafer with high density and high yield, the reaction atmosphere that contributes to film formation, etching, and the like must be completely controlled. This is the reason why the technology for supplying ultra-high purity gas is important.

The gases used in semiconductor manufacturing equipment include relatively stable general gases (N ₂ , Ar, He, O ₂ , H ₂ ) and special material gases (eg, highly toxic, natural, corrosive, etc.) AsH _3, PH _3, Si
_{H 4, Si 3 H 5,} HCl, NH 3, Cl 2, CF 4, SF 6, NF 3, WF 6, F
₂ etc.).

Since general gas is relatively easy to handle, it is almost always pumped directly from the refining equipment to the semiconductor manufacturing equipment. Due to the development and improvement of storage tanks, refining equipment, piping materials, etc., ultra-high-purity gas is used. (Tadahiro Omi, "Challenge to ppt-Gas piping system for semiconductors to challenge ppt impurity concentration", Nikkei Microdevices, July 1987, pp.98- 119).

On the other hand, special material gases require careful handling and use less gas than ordinary gases. In most cases, it is pumped to the equipment.

However, in the case of a special material gas, the process gas supplied to a cylinder is usually filled with a gas (process gas) diluted to a low concentration with a diluting gas (balance gas), and the process gas is supplied from the cylinder to a process device. The device is configured. For this reason, cylinders are frequently replaced once a month or once a week, and even if a cylinder improved in terms of internal contamination is used, the gas supply piping system is contaminated by air. However, no matter how ultrapure gas filling technology has been established, the gas charged into the cylinder will be lower in purity than before filling. Furthermore, the work of exchanging cylinders also requires manpower, which causes an increase in cost.

If the process gas supplied to the process device is contaminated, the process gas is seriously affected. For example
Al film formation technology (T. Ohmi, H. Kuwabara, T. Shibata and T. Kiyo
ta, “RF DC coupled mode biassputtering for ULSI me
talizatioan ".S.Broydo and CMOsburn, Ed.," ULSI Sc
ience and Technology / 1987 ", The Electrochemical Soc
society Inc., Philadelphia 1987.Proc. Vol. 87-11, pp. 574
-592. And Tadahiro Omi, "Thoroughly remove impurities, grasping Al film formation conditions without hillocks", Nikkei Microdevices, October 1987, pp.109-111), in Ar sputtering atmosphere. If water contains 10 ppb or more, the morphology of the Al film surface deteriorates. In this case, the resistivity
It is impossible to optimize Al deposition parameters equal to Al and without hillocks by heat treatment. further,
When this film formation technique is applied to Si film formation, even if other film formation conditions are kept exactly the same, only an amorphous film can be obtained if the process atmosphere is contaminated by gas released from the chamber inner surface ( T. Ohmi, T. Ichikawa, T. Shibata, K.
Matsudo and H. Iwabuchi, “In Situ Substrate-Surfac
e Cleaning for Very Low Temperature Silicon Epitax
y by Low-Kinetic-Energy particle Bombardment ".Ap
pl.Phys. Lett. 53, 4 July (1988) and T. Ohmi, T. Ich
ikawa, T. Shibata, K. Matsudo and H. Iwabuchi, “Low-Te
mperature Silicon Epitaxy by Low-Energy Bias-Spu
ttering ", Apple.Phys.Lett.1 Augusta (1988)).

When forming a Si thin film by low-pressure CVD, if the water content exceeds 10 ppb, selective growth and epitaxial growth are not performed. (Junichi Murota, Naoto Nakamura, Manabu Kato, Nobuo Mikoshiba, and Tadahiro Omi. “Highly Selective Ultra Clean CVD Technology”, Proceedings of the 6th Super LSI Ultra Clean Technology Symposium, “High Performance Process Technology III”, 1
Jan. 988, pp. 215-226).

Further, the conventional process gas supply device adjusts the gas amount by, for example, switching some of the capillaries and selecting the number of flowing gas, or mixing by two floater flow meters or mass flow controllers. Methods such as adjusting the flow rates of two types of gases are used.These methods have dilution rates as low as several hundredths at most, and the gas contact parts are too dirty to supply ultra-high-purity gas. There were many things. For example, several ppm to process equipment
When a gas having a concentration of about 1 to several tens of ppm is to be supplied, if a 100% raw material gas is to be supplied from a cylinder, it must be diluted with a balance gas by a factor of about 10,000 to 100,000.

The present invention has been made in view of the above points, and it is possible to easily supply a process gas without being affected by air pollution, and to generate a gas such as moisture or an organic substance that has almost no released gas that adversely affects the process. An object of the present invention is to provide a supply system and provide a high-purity, high-performance process gas supply device.

DISCLOSURE OF THE INVENTION According to the configuration of claim 1, a raw material gas and a diluent gas are separately supplied and mixed to become a process gas in the vicinity of a process apparatus, and the process gas generation process is performed by each flow rate adjusting unit. Is diluted to a desired concentration.

Further, by providing at least two branch pipes and the exhaust gas pipe, the process gas can be diluted efficiently and stepwise as desired.

According to the second to fourth aspects of the present invention, it is possible to reduce impurities due to gas released from the surface of the gas contact portion and supply an ultra-clean and high-performance process gas to the process apparatus.

According to the configuration of claim 5, the raw material gas and the diluent gas are separately supplied and mixed to become the process gas in the vicinity of the process device, while the raw material gas in the process of generating the process gas is produced by each flow rate adjusting means. And the balance gas is diluted to the desired concentration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a piping system of a process gas supply device according to the present invention, FIG. 2 is a diagram showing a flow of gas being purged by the device shown in FIG. FIG. 3 is a view showing a gas flow when the source gas is diluted at a low magnification, and FIG.
The figure shows the gas flow when the source gas is diluted at a high magnification, FIG. 5 shows the gas flow when the mass flow controller is calibrated, and FIG. 6 shows the calibration of the other mass flow controllers. 7 (A), (B), (C), and (D) are graphs showing the amounts of moisture detected when different types of sheet portions are used, respectively. (A), (B), (C), (D) are graphs showing the amount of moisture detected when each of the sheet portions is heated,
9 (A), 9 (B), 9 (C), and 9 (D) are graphs showing spectra at the time of the heating, and FIG. 10 is a graph showing ionic strength with respect to moisture concentration.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 101 denotes a gas diluting unit, and 102 denotes a cylinder cabinet unit for supplying an ultra-high purity source gas. Note that only the minimum necessary members of the cylinder cabinet 102 are illustrated in order to simplify the description.
It is desirable that the cylinder cabinet 102 be provided with a gas purge system from the standpoint of high purification of the gas supply system. 103, 104, 105, 106, 107, 108, and 110 are stop valves, and the stop valves 103, 104, the stop valves 105, 106, and the stop valves 107, 108 are each a double valve integrating two valves. Reference numeral 109 denotes a three-way valve, and reference numeral 109 denotes a branch valve. Also, these valves 10
Reference numerals 3, 104, 105,... Are all-metal diaphragm valves containing no organic material.

Reference numerals 111, 112, 113, and 114 denote mass flow controllers as flow regulators, which are preferably provided with a purging means in consideration of startability after installation of the piping, gas replacement, and the like. Reference numerals 115 and 116 denote mass flow meters. The mass flow controllers 111, 112, 113 and 114 and the mass flow meters 115 and 116 are high-performance devices having, for example, an accuracy of ± 0.1% or more of full scale and a response time of 0.3 seconds or less. It is desirable that

Reference numeral 117 denotes a pressure gauge for checking the supply pressure of the diluent gas (balance gas) and as a reference when adjusting the supply pressure of the source gas. However, from the standpoint of high purification of the gas supply system, it is desirable to employ a pressure gauge 117 having a diaphragm type pressure sensor having no stagnation portion. Reference numeral 118 denotes a pipe for uniformly mixing the gas, and reference numeral 119 denotes a gas cylinder. This gas cylinder 119 is an ultra-clean gas cylinder of internal composite polishing for storing a high-concentration source gas. 120, 1
21 is a main valve of a gas cylinder 119 in which two valves are integrated, 120 is a purge valve for purging the inside of the main valve with a purge gas, and 121 is a gas supply for supplying a source gas in the gas cylinder. It is a valve. Here, the purge gas is preferably a gas of the same type as the balance gas (for example, Ar, H ₂ , N ₂ , He, etc.). Reference numeral 122 denotes a pressure regulator, which is installed to regulate the supply pressure of the raw material gas in the cylinder, and is made of an all metal using a diaphragm type pressure sensor from the viewpoint of gas-cleaning. 123, 123 'is a balanced gas supply pipe for supplying the balance gas (e.g. Ar, etc. _{H 2, N 2, He)} . 124 is a process gas supply pipe,
The process gas supply pipe 124 is for supplying a process gas obtained by diluting a source gas to a predetermined concentration to a process device. Reference numeral 125 denotes a balance gas branch pipe, which is a first communication pipe for performing dilution first when diluting at a high magnification. 126 is for supplying a high-concentration raw material gas in the case of low-magnification dilution or a gas subjected to the first-stage dilution in the case of high-magnification dilution to the balance gas supply pipe 123 'for performing the second-stage dilution. It is a dilution gas supply pipe. That is, the dilution gas supply pipe 126 is connected to the balance gas supply pipe 1.
23 'is a second communication pipe connected to the process gas supply pipe 124 through the valve 109 and for supplying the process gas to the process gas supply pipe 124. 127 is a purge gas (eg, Ar, H ₂ , N ₂ , He, etc.)
And a gas pipe for purging the inside of the source valve of the gas cylinder and the source gas supply pipe of the cylinder. 128 is a cylinder gas supply pipe, and 129 is an exhaust pipe. This exhaust pipe 129 is for exhausting the raw material gas that has been subjected to the first stage dilution and the gas that has become excessive to perform the second stage dilution when performing high-magnification dilution, for example, 0.5% or less. This is a pipe that discharges the diluted raw material gas into the atmosphere after treating it with an exhaust treatment device.

Next, the function and operation method of the process gas supply device configured as described above will be described with reference to the drawings. In addition,
In the figure, the pipe through which the gas flows is indicated by a thick solid line.

FIG. 2 shows a gas flow when the entire piping system is purged. Valve 103, 104, 105, 106, 10
8, 109, 110, 120 are opened, and the gas supply valve 121 is closed, and the secondary pressure of the pressure regulator 122 is increased from the indicated value of the pressure gauge 117, for example, from 0.5 [kg / cm ² ] to 1.0 [kg / cm ² ]. ] About high. The mass flow controllers 111, 112, 113, and 114 are set in a purge mode, and a purge gas (N ₂ , Ar) or a balance gas (for example, 1 [l / min] or more)
Ar, H ₂ , N ₂ , He, etc.) are flowed, and the entire piping system is purged.

FIG. 3 shows a gas flow when a raw material gas is supplied to a process device at a low dilution ratio. Valve 103, 10
6, 107, 109, 110, 121 open, valves 104, 105, 108, 12
In a state where 0 is closed, the balance gas 123 flows through the pipe 123 ′, and the raw material gas flows through the pipes 128 and 126 at the flow rates set by the mass flow controllers 111 and 112, respectively, to the process gas supply pipe 124 at a predetermined concentration. Supply diluted process gas. The dilution rate is set by setting the flow rate of the mass flow controller 111 to Q ₁ [l / min], the flow rate of the pressure regulator 122 to Q ₂ [l / min], and the flow rate of the mass flow meter 116 (process gas supply flow rate) to Q _T [ l / min] and the dilution ratio is A%
Then, Q ₁ + Q ₂ = Q _T (1) 100 · Q ₂ / (Q ₁ + Q ₂ ) = A (2) Q ₁ and Q ₂ can be calculated from the above equations (1) and (2). .

FIG. 4 shows a gas flow when a raw material gas is supplied to a process device at a high dilution ratio. Valve 103, 10
4, 105, 106, 107, 108, 109, 110, 121 open, valve 12
With the 0 closed, supply the balance gas to the supply pipe 123 and the branch pipe.
125, the raw material gas is supplied to a pipe 128, and diluted with a balance gas (for example, Ar, H ₂ , N ₂ , He, etc.) from the pipe 125,
The gas flows into the dilution gas supply pipe 126 and the exhaust pipe 129 at a predetermined flow rate. Further, the gas supplied from the dilution gas supply pipe 126 is supplied to a balance gas (eg, Ar, H ₂ , N ₂ , He, etc.) of the supply pipe 123 ′.
After that, the process gas diluted to a predetermined concentration is supplied to the process gas supply pipe 124 at a predetermined flow rate. The dilution ratio and the process gas supply flow rate are set by setting the mass flow controllers 111, 112, 113, and 114 so that the flow rates become predetermined. The dilution ratio is set by setting the flow rate of the mass flow controller 111 to Q ₁ [l / min], the flow rate of the mass flow controller 122 to Q ₂ [l / min], the flow rate of the mass flow controller 113 to Q ₃ [l / min], the mass flow controller 114 flow rate Q ₄ [l / min], mass flow controller
Assuming that the flow rate of 116 (process gas supply flow rate) is Q _T [l / min] and the dilution ratio is A%, Q ₁ + Q ₃ = Q _T … (3) 100 · Q ₂ · Q ₃ / (Q ₃ + Q) ₄ ) · (Q ₁ + Q ₃ ) = A (4) The flow rate of the mass flow controller 111 is Q ₁ , the flow rate of the mass flow controller 112 is Q ₂ , the flow rate of the mass flow controller 113 is Q ₃ , and the flow rate of the mass flow controller 114 is Q ₄ Then, assuming that the concentration at the first confluence 118 at the point of Q ₁ + Q ₃ = Q _T is A ′, Q ₂ / (Q ₃ + Q ₄ ) = A ′ Then, the raw material gas concentration A at 116 is A ′・ Q ₃ / (Q ₃ + Q ₁ ) = A By substituting the above A 'into this equation, {Q ₂ / (Q ₃ + Q ₄ )} ｛{Q ₃ / (Q ₃ + Q ₁ )} = A The above equation (4) is obtained.

If Q ₂ = Q ₃ and Q ₄ is set arbitrarily, Q ₁ ,
Q ₂ and Q ₃ can be calculated.

5 and 6 illustrate a mechanism for confirming the accuracy of the mass flow controller of the dilution device of the present invention, and FIG. 5 illustrates mass flow controllers 111 and 11.
4 and 6 show the gas flows for confirming the accuracy of the mass flow controllers 112 and 113.

In FIG. 5, the valves 103, 104, 105 and 108 are opened and the valves are opened.
With the 106, 107, 109, 110, 120, 121 closed, the balance gas (eg, Ar, H ₂ , N
₂ , He, etc.), and compare the indicated values of the mass flow controller 111 and the mass flow meter 116 to confirm the accuracy of the mass flow controller. Further, the accuracy of the mass flow controller 114 is confirmed by comparing the indicated values of the mass flow controller 114 and the mass flow meter 115.

In FIG. 6, the valves 106, 107, 109, 110 and 120 are opened,
The valve 103,104,105,108 in the closed state, the purge gas from the purge gas supply pipe 127 (e.g. Ar, etc. N ₂₎ supplying a mass flow by comparing the instruction value of the mass flow controllers 112, 113 and a mass flow meter 116 Check the accuracy of the controllers 112 and 113.

In the above embodiment, the gas supply from the gas cylinder has been described. However, the present invention can be applied to a system in which a method of supplying a diluted gas is different. It is also effective to use it as a process gas supply device as a standard gas generation device used when calibrating a gas analyzer, creating a calibration curve, and the like.

FIGS. 7 (A), (B), (C) and (D) show changes in the amount of water contained in the purge gas when metal diaphragm valves of different types of seats are purged at room temperature. In the experiment, Ar gas was flowed through the metal diaphragm valve at a flow rate of 1.21 / min, and the amount of water contained in the Ar gas at the outlet was measured by APIMS (atmospheric pressure ionization mass spectrometer). FIG. 8 shows the results of APIMS MID mode measurement (a method of simultaneously measuring several types of ion behaviors). When the water content increases, M / Z = 18 (H ₂ O ⁺ ), 19 (H ₃ O ⁺ ). ⁺ ) Increases the ion intensity of the host gas, argon (M / Z = 40; Ar
⁺ ) The ionic strength decreases. The rate of increase or decrease in the ionic strength completely depends on the amount of water. Each measurement was started two minutes after the sample device. The types of metal diaphragm valves tested were the conventional product using polyimide resin for the seat part (hereinafter referred to as Case 7A), and the product using the polyimide resin for the seat part that minimized the dead space (hereinafter referred to as Case 7B). , A product obtained by coating the polyimide resin on the sheet portion of the product with a metal by sputtering (hereinafter referred to as Case 7C), and a product obtained by removing the resin of the sheet portion to obtain an all metal (hereinafter Case 7D)
). Each metal diaphragm valve was left in a clean room at a relative humidity of 50% and a temperature of 20 ° C. for about one week, and then the present experiment was performed.

It can be seen that a large amount of water is detected in each of (A), (B) and (C) of FIG. Even after passing gas for about 1 hour, in case 7A and case 7B, about 200 ppb, case
In 7C, as much as 150 ppb of water was detected, indicating that the amount of water does not easily decrease. On the other hand, when the resin was removed from the gas contact part (Case 7D), one hour after gas passage,
The water content decreased to 16 ppb. Thus, it can be seen that case 7D is superior to the valves of the other cases 7A, 7B, 7C by more than one order of magnitude in moisture removal performance and has extremely excellent adsorption gas degassing characteristics.

FIGS. 8 (A), (B), (C), and (D) show the change in the amount of water when these valves are heated to 130 ° C. with a heater in terms of relative ionic strength. (A)
(Case 8A), (B) (Case 8B),
(C) (Case 8C), (D) (Case 8D)
Respectively correspond to FIGS. 7A, 7B, 7C and 7D. FIG. 10 is a simple graph for easily explaining the behavior of water in APIMS. APIMS
In the case, when the water content in the system increases, the ionic strength of the host gas (in this case, argon) decreases, and the water ion H ₂ O ⁺ (M / Z
= 18) increases. When the water increases further, water ions
H ₂ O ⁺ (M / Z = 18) begins to decrease, and water cluster ions H ₂ O · H ⁺ (M / Z = 19) increase. When the water content further increases, the water cluster ion H ₂ O · H ⁺ (M / Z = 19) decreases, and the water dimer cluster ion (H ₂ O) ₂ · H ⁺ (M / Z = 3)
7) increases.

As is clear from FIGS. 8 (A), (B) and (C),
It can be seen that a large amount of water was detected in each of the cases 8A, 8B, and 8C. About 15 minutes after the start of heating, these valves released water in the order of several thousand ppb to%, and this state was maintained even after heating was continued for one hour. On the other hand, case 8D
Even after heating, the amount of released water is 100 ppb or less, which is as small as one or two digits.

Fig. 9 (A) (Case 9A), (B) (Case 9B)
(C) (Case 9C), (D) (Case 9C)
9D) shows a typical spectrum during this heating. Case 9A, Case 9B, Case 9C, Case 9A
9D corresponds to FIG. 8 cases 8A, 8B, 8C and 8D, respectively.
In the cases 9A, 9B and 9C, due to the effect of a large amount of released water, not only the peak of the host gas (argon) but also a substance considered to be an organic compound such as M / Z = 43,45,59,61,71. Has been detected. In contrast, case 9D
Means that the peak (M / Z = 40,80) of the host gas (argon) is detected, and a small amount of atmospheric components (for example,
CO of Z = 44 ₂₎ only it was detected. It has been found that when no organic compound is present in the gas contact portion as in Case 9D, not only is the release of moisture small, but also there is no release of any organic substance that adversely affects the semiconductor process.

Regarding filters, ceramic filters using ceramics, which are inorganic substances, have been developed for the elements.The gasket can be made of nickel packing, and the resin, which is an organic compound used in the past, is brought into contact with the gas. Can be removed from the department. Further, an all-metal filter made entirely of stainless steel has been developed by manufacturing the element from stainless steel and connecting the housing to the housing by welding.

INDUSTRIAL APPLICABILITY As described above, according to the first aspect of the present invention, the opportunity of air pollution can be eliminated, the source gas can be diluted to a desired concentration with a diluent gas, and the stepwise dilution of the source gas can be efficiently performed. Well done.

According to the second to fourth aspects of the present invention, the influence of the gas emitted mainly from the organic substance is eliminated, and the process gas can be supplied to the process apparatus while maintaining high purity.

According to the invention of claim 5, the opportunity of air pollution is eliminated,
The source gas can be diluted to a desired concentration with a diluent gas.

In addition, by forming the gas supply system of the present invention entirely from metal or ceramic, the metal passivation treatment (oxidation passivation,
Fluoride passivation) can be performed, the purge time of the pipe after the application is shortened, and a high-purity process gas can be supplied to the process apparatus in a short time. Here, the thermal oxidation passivation treatment is particularly effective for forming the oxide passivation film. In this case, for example, it is more preferable to perform electrolytic polishing so as to obtain a predetermined flatness and to perform the treatment in a high-purity oxygen atmosphere.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B01F 15/04 B01F 3/02 C23C 16/00-16/56 C23F 4/00-4/04 C30B 25 / 00-25/22 B01J 4/00-4/04 H01L 21/205 H01L 21/31 H01L 21/365 H01L 21/302

Claims (5)

(57) [Claims] In a process gas supply device having a gas supply system for supplying a process gas obtained by mixing a source gas and a dilution gas to a process device, at least one gas for flowing the source gas is provided. A source gas supply pipe, at least one dilution gas supply pipe for flowing the dilution gas, and at least two communication pipes connecting the source gas supply pipe and the dilution gas supply pipe at respective downstream sides; A source gas supply pipe, the dilution gas supply pipe, and at least one flow controller provided in each of the communication pipes, and a downstream side of a connection portion between the source gas supply pipe and the dilution gas supply pipe. At least one exhaust pipe is provided on the side, and at least one of the process devices is provided at least downstream of a connection portion between the communication pipe and the dilution gas supply pipe. Gas supply equipment . 2. The process gas supply apparatus according to claim 1, wherein the gas supply system is made of a material that does not emit at least an organic substance at a gas contact portion that comes into contact with the various gases. 3. The process gas supply device according to claim 2, wherein the material that does not release the organic substance is a metal. 4. The process gas supply device according to claim 2, wherein the material that does not release the organic substance is ceramic. 5. At least one source gas supply pipe for flowing a source gas, at least one dilution gas supply pipe for flowing a dilution gas, and the source gas supply pipe and the dilution gas supply pipe are connected to each other. At least one communication pipe connected at each downstream side, and at least one flow regulator provided at each of the source gas supply pipe and the dilution gas supply pipe, wherein the communication pipe and the dilution gas supply are provided. A process gas supply device having at least one of the process devices at least downstream of a connection portion with a pipe, wherein the source gas is supplied at a flow rate set by a flow rate regulator provided in the source gas supply pipe. The process gas diluted to a predetermined concentration is supplied to the process apparatus by flowing the dilution gas into the dilution gas supply pipe at a flow rate set by a flow controller provided in the dilution gas supply pipe. Process gas supply method comprising and.