JP2013211406A - Mixed gas supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mixed gas supply system for supplying an using point by a high pressure with a mixed gas composed of a low vapor pressure reactive gas that is liquescent or polymeric and a low-boiling point diluent gas, which can prevent liquefaction and polymerization of the reactive gas, achieve uniform mixing with the diluent gas and increase accuracy of mixture fraction.SOLUTION: A vacuum generator 4 in the system is used to decompress a reactive gas and mix the reactive gas with a diluent gas. The mixed gas from the vacuum generator 4 is compressed by a compressor 51 to be supplied to an using point by pressure of 0.5 MPaG-3.0 MPaG. Then, a reactive gas supply line 2 is decompressed so as to prevent liquefaction and polymerization of the reactive gas, to improve controllability in a first mass flow controller 23 located in the reactive gas supply line 2 and to achieve uniform mixing thereof with the diluent gas. Therefore, the reactive gas and the diluent gas can be mixed in a high-accuracy and predetermined mixture fraction.

Description

  In the present invention, a reactive gas having a low vapor pressure that is easily liquefied or has a physical property to be polymerized and a diluent gas that is inert and has a higher vapor pressure than the reactive gas are mixed in a predetermined ratio. This is a technique related to a mixed gas supply system in which a mixed gas is supplied to a use point at a pressure of 0.5 MPaG to 3.0 MPaG.

Conventionally, a reactive gas such as hydrogen fluoride (HF), which has a property of being easily liquefied or polymerized depending on temperature and pressure, has been used in an etching process and a cleaning process in a semiconductor manufacturing process.
In order to perform an accurate etching process and cleaning process, it is necessary to control the supply amount of the reactive gas with a high degree of accuracy. Therefore, the reactive flow rate is controlled by a mass flow controller without polymerizing the reactive gas. One that controls the amount of gas supply is known (see, for example, Patent Document 1).

Conventionally, there is known a method in which a supply amount of a mixed gas is controlled by a mass flow controller in a state where a partial pressure of the reactive gas is lowered by mixing a diluent gas with the reactive gas (for example, And Patent Document 2).
Furthermore, conventionally, there is known one that makes the concentration of the reactive gas (fluorine gas) in the mixed gas uniform (see, for example, Patent Document 3).

JP 2008-146541 A Japanese Patent No. 4364740 JP 2010-245226 A

In the conventional technique described in Patent Document 1, the pressure of the reactive gas entering the mass flow controller is reduced to a low value at which the reactive gas is not polymerized, and the polymerization of the reactive gas is performed. Although it is a technical feature to avoid, there is a problem that it does not have other special technical features.
In addition, the conventional technique described in Patent Document 2 controls the supply amount of a mixed gas of a reactive gas and a dilution gas by a mass flow controller, and mixes the reactive gas in the mixed gas. There was a problem that the accuracy of the ratio could not be increased.

Furthermore, in the prior art described in Patent Document 3, in order to make the concentration of the reactive gas in the mixed gas uniform, one end of a bypass pipe provided with a circulation pump is connected to the buffer tank of the mixed gas. The other end is connected to the downstream side of the junction of the reactive gas and the inert gas, and the mixed gas in the buffer tank is circulated by the circulation pump and the bypass pipe. In order to make the concentration of the reactive gas in the gas uniform, the bypass pipe and the circulation pump are necessary, and there is a problem that equipment space and equipment cost are required.
In addition, when a circulation pump or a booster is installed after the gas flow control device in this way, in a case where the differential pressure before and after the gas flow control device cannot be sufficiently obtained, such as a low vapor pressure reactive gas, Due to the pulsation of the booster, the controllability of the gas flow rate adjusting device deteriorates, and there is a problem that the accuracy of the mixing ratio of the reactive gas is lowered.

  In the conventional example described in Patent Document 1, the present invention simply reduces the pressure to a low pressure at which the reactive gas is not polymerized, and the accuracy of the mixing ratio of the reactive gas in the mixed gas in the conventional example described in Patent Document 2 The problem that it cannot be increased, the problem that equipment space and equipment costs are required to make the concentration of the reactive gas in the mixed gas in the conventional example described in Patent Document 3 uniform, and the accuracy of the mixing ratio of the reactive gas is high It is intended to solve the problem of lowering all at once, and the mass flow rates of the reactive gas and the dilution gas are controlled by the first mass flow control device and the second mass flow control device, respectively, and the reactive gas is controlled by the vacuum generator. The vacuum gas generator is mixed with the reactive gas and the dilution gas while buffering the pressure fluctuation in the subsequent stage. -The mixed gas supply that pressurizes the mixed gas from the compressor with a compressor and supplies the mixed gas in which the reactive gas and the dilution gas are mixed at a predetermined ratio to the point of use at a pressure of 0.5 MPaG to 3.0 MPaG. It is intended to be a system.

The mixed gas supply system of the present invention according to claim 1 is a low vapor pressure reactive gas that has a property of being easily liquefied or polymerized, and is inert to the reactive gas and has a higher vapor pressure than the reactive gas. In the mixed gas supply system that supplies the mixed gas mixed with the dilution gas at a predetermined ratio to the use point at a pressure of 0.5 MPaG to 3.0 MPaG.
A reactive gas supply line provided with a first mass flow controller for controlling the mass flow rate of the reactive gas to a first set value;
A dilution gas supply line provided with a second mass flow control device for controlling the mass flow rate of the dilution gas to a second set value;
The working gas supply port, the suction port, and the discharge port are connected, and the dilution gas supply line is connected to the working gas supply port, and the reactive gas supply line is connected to the suction port. A vacuum generator that mixes with gas,
A mixed gas supply line provided with a compressor connected to the discharge port of the vacuum generator and pressurizing the mixed gas discharged from the discharge port;
The outlet side of the mixed gas supply line is used as the use point.

  A mixed gas supply system according to a second aspect of the present invention includes a reactive gas that heats at least the reactive gas supply line leading to the inlet of the first mass flow control device in addition to the configuration of the present invention according to the first aspect. A heating device is provided.

  In the mixed gas supply system of the present invention according to claim 3, in addition to the configuration of the present invention according to claim 1 or 2, the reactive gas is hydrogen fluoride or chlorine trifluoride, and the dilution gas is Argon, nitrogen or helium.

In the mixed gas supply system of the present invention according to claim 1, the mass flow rates of the reactive gas and the mixed gas are controlled to predetermined values by the first mass flow control device and the second mass flow control device, respectively, and the vacuum generator generates the Reducing the reactive gas and mixing with the dilution gas, increasing the pressure of the mixed gas from the vacuum generator with a compressor, and mixing the reactive gas and the dilution gas at a predetermined ratio, Since the supply point is supplied at a pressure of 0.5 MPaG to 3.0 MPaG, by using the vacuum generator, the reactive gas supply line is decompressed and the first gas gas is interposed in the reactive gas supply line. Uniform mixing with the dilution gas while preventing liquefaction and polymerization of the reactive gas controlled by the mass flow controller In addition, since the pulsation of the compressor can be buffered and the influence on the first mass flow controller can be reduced, the mixing ratio of the reactive gas and the dilution gas can be accurately mixed at a predetermined ratio. It is.
Also, by using the vacuum generator, the low pressure reactive gas at the outlet of the first mass flow controller and the high pressure dilution gas at the outlet of the second mass flow controller are mixed. The pressure of the mixed gas at the discharge port of the vacuum generator can be set to a relatively high state, the compression ratio in the compressor is reduced, the pressure is efficiently increased, and the pressure at the use point is reduced. A high gas mixture can be supplied.
For example, at the point of use, by uniformly expanding a mixed gas having a pressure of 0.5 MPaG to 3.0 MPaG, uniform reactive clusters can be generated and the substrate surface can be processed with high accuracy.

  The mixed gas supply system of the present invention according to claim 2 has the reactive gas for heating at least the reactive gas supply line leading to the inlet of the first mass flow control device in addition to the effect of the present invention according to claim 1. Since the heating device is provided, the pressure can be increased in a range where the reactive gas entering the first mass flow control device is not liquefied and polymerized, the compression ratio in the compressor is further reduced, and the compressor is downsized. You can also do it.

  In the mixed gas supply system of the present invention according to claim 3, in addition to the effect of the present invention according to claim 1 or 2, the reactive gas is hydrogen fluoride or chlorine trifluoride, and the dilution gas is Since it is argon, nitrogen or helium, it can be widely used for etching in the manufacturing process of a semiconductor substrate or the like at the point of use.

It is a schematic explanatory drawing which shows the outline of the mixed gas supply system of this invention.

Hereinafter, a mixed gas supply system according to an embodiment of the present invention will be described with reference to a schematic explanatory diagram of FIG.
In FIG. 1, reference numeral 1 denotes a mixed gas supply system, which includes a reactive gas supply line 2, a dilution gas supply line 3, a vacuum generator 4, and a mixed gas supply line 5, and the mixed gas supply line 5. The use point 11 is the exit side.

Connected to the reactive gas supply line 2 is a reactive gas container 21 filled with hydrogen fluoride (HF) as a reactive gas.
The hydrogen fluoride in the reactive gas container 21 is adjusted to a pressure of, for example, 50 kPa · abs by the first pressure regulating valve 22, and the first mass flow controller 23 provided in the reactive gas supply line 2. The mass flow rate is controlled to, for example, the first set value of 0.25 SLM, and is sucked into the suction port 41 of the vacuum generator 4.

Further, the reactive gas supply line 2 is provided with a reactive gas heating device 24 for heating the outer periphery, and low vapor pressure hydrogen fluoride having physical properties that liquefy and polymerize depending on temperature and pressure is added to the reactive gas supply line 2. The mass flow rate is accurately controlled to the first set value without being liquefied and polymerized by the first mass flow controller 23.
The reactive gas heating device 24 uses an electric heater to heat hydrogen fluoride flowing through the reactive gas supply line 2 from the outer periphery of the reactive gas supply line 2 by heat conduction. The energization is controlled so that the temperature becomes 120 ° C., for example, and the outside of the electric heater is covered with a heat insulating material.

The dilution gas supply line 3 includes a dilution gas container 31 filled with argon (Ar) as a dilution gas that is inert with the reactive gas (hydrogen fluoride) and has a higher vapor pressure than the reactive gas. It is connected.
The argon in the dilution gas container 31 is adjusted to a pressure of, for example, 0.65 MPaG by the second pressure adjustment valve 32, and the mass flow rate is controlled by the second mass flow controller 33 provided in the dilution gas supply line 3. For example, the second set value is controlled to 4.75 SLM, and is supplied to the working gas supply port 42 of the vacuum generator 4.

The vacuum generator 4 includes a nozzle, a diffuser, and the like, and has the working gas supply port 42, the suction port 41, and the discharge port 43, and the dilution gas supply line 3 is connected to the working gas supply port 42. The reactive gas supply line 2 is connected to the suction port 41 to mix hydrogen fluoride as the reactive gas and argon as the diluent gas.
The pressure of argon at the working gas supply port 42 of the vacuum generator 4 is, for example, 0.55 MPaG, the pressure of hydrogen fluoride at the suction port 41 is, for example, 13 kPa · abs, and the pressure of the mixed gas at the discharge port 43 Is, for example, 100 kPa · abs.

Therefore, by using the vacuum generator 4, the hydrogen flow having physical properties to be liquefied and polymerized can be reduced in pressure and the mass flow rate can be controlled without being liquefied and polymerized by the first mass flow controller 22, and Hydrogen fluoride and argon can be mixed uniformly.
The mixed gas supply line 5 is connected to the discharge port 43 of the vacuum generator 4, and has a compressor 51 that pressurizes the mixed gas discharged from the discharge port 43.

The compressor 51 boosts the pressure of the mixed gas to, for example, 0.5 MPaG to 3.0 MPaG by compressing the sucked mixed gas.
Thus, by using the vacuum generator 4, the low pressure reactive gas at the outlet of the first mass flow controller 23 and the high pressure dilution gas at the outlet of the second mass flow controller 33. And the pressure of the mixed gas at the discharge port 43 of the vacuum generator 4 can be made relatively high, and the compression ratio in the compressor 51 is reduced to efficiently increase the pressure. Thus, the mixed gas having a high pressure can be supplied to the use point 11.

The outlet side of the mixed gas supply line 5 is used as the use point 11, and the use point 11 is provided with a reservoir tank 6 for storing the mixed gas discharged from the compressor 51.
The reservoir tank 6 is connected to a use line 7 in which a flow meter 71 and a third pressure regulating valve 72 are interposed, and the mixed gas stored in the reservoir tank 6 is supplied to the flow meter 71, Through the third pressure regulating valve 62, for example, after being cooled, it is blown into the vacuum processing chamber while being adiabatically expanded by a nozzle and polymerized to generate a reactive cluster, and the substrate surface is etched.

In FIG. 1, 8 is an exhaust line, 25, 34, 73, 81 and 82 are on-off valves. The exhaust line 8 opens the on-off valves 81 and 82 when the mixed gas supply system 1 is not operated for a long period of time. Then, the gas in the system is detoxified by a vacuum pump or the like and exhausted.
In the above embodiment, the first mass flow control device 23, the second mass flow control device 33, and the vacuum generator 4 are used. All of these are commercially available in various specifications. Among the products, those having specifications suitable for the above embodiment are selected.

In the above embodiment, hydrogen fluoride is used as the reactive gas, but chlorine trifluoride may be used.
In the above embodiment, argon is used as the diluent gas. However, a diluent gas that is inert with the reactive gas and has a higher vapor pressure than the reactive gas can be used. For example, helium (He ), Neon (Ne), krypton (Kr), xenon (Xe) and the like, nitrogen (N ₂ ), carbon dioxide (CO ₂ ), and the like can be used.

In the above embodiment, the reactive gas heating device 24 is provided on the entire outer periphery of the reactive gas supply line 2 from the outlet of the reactive gas container 21 to the suction port 41 of the vacuum generator 4. However, by providing only in the outer peripheral part of the reactive gas supply line 2 reaching the inlet of the first mass flow control device 23, the liquefaction and polymerization of the reactive gas are prevented by the first mass flow control device 23. Alternatively, the reactive gas heating device 24 can be omitted by reducing the pressure of the reactive gas at the inlet of the first mass flow control device 23 to a pressure that does not cause liquefaction and polymerization.
In the above embodiment, the reservoir tank 6 is provided at the use point 11 on the outlet side of the mixed gas supply line 5. However, if the use of the mixed gas at the use point 11 is continuous, The reservoir tank 6 may be omitted.

  In the above embodiment, the mixing ratio of the mixed gas at the use point 11 is 5% for the reactive gas and 95% for the dilution gas. However, the reactive gas in the mixed gas is not liquefied at the supply pressure ( In the first mass flow controller 23, the first mass flow rate can be adjusted from the required mass flow rate of the reactive gas and the required differential pressure at the inlet / outlet. It is necessary to set the reactive gas so as to have a pressure and temperature at which the reactive gas is not liquefied and polymerized at the inlet of the flow control device 23.

If the supply pressure exceeds 3.0 MPaG, reactive gases such as hydrogen fluoride are liable to be liquefied, so it is necessary to keep the mixing ratio of reactive gases low, which hinders cluster generation and substrate surface processing. Therefore, the supply pressure is preferably 3.0 MPaG or less.
Furthermore, if the pressure of the dilution gas and the mixed gas is less than 1 MPaG, it is out of the scope of application of the high-pressure gas safety method, and therefore, restrictions such as management are eased, which is more preferable. Furthermore, many measuring instruments such as pressure gauges have a pressure resistance and a display range of 1 MPaG, and in order to use them effectively, operation at 0.95 MPaG or less is more desirable.

  In the above embodiment, the mixing ratio of the mixed gas is not monitored. However, the mixed gas supply system 1 is installed and the mixing ratio of the mixed gas is analyzed during the trial operation at the use point 11 to obtain a predetermined value. By calibrating the first mass flow control device 23 and the second mass flow control device 33 so as to achieve a mixing ratio, the accuracy of the mixing ratio of the mixed gas can be increased.

DESCRIPTION OF SYMBOLS 1 Mixed gas supply system 2 Reactive gas supply line 3 Dilution gas supply line 4 Vacuum generator 5 Mixed gas supply line 11 Use point 23 1st mass flow control apparatus 24 Reactive gas heating apparatus 33 2nd mass flow control apparatus 41 Suction port 42 Working gas supply port 43 Discharge port 51 Compressor

Claims (3)

A mixed gas obtained by mixing a reactive gas having a low vapor pressure that has a property of being easily liquefied or polymerized, and a reactive gas and a diluent gas that is inert and has a higher vapor pressure than the reactive gas at a predetermined ratio, In the mixed gas supply system that supplies the use point at a pressure of 0.5 MPaG to 3.0 MPaG,
A reactive gas supply line provided with a first mass flow controller for controlling the mass flow rate of the reactive gas to a first set value;
A dilution gas supply line provided with a second mass flow control device for controlling the mass flow rate of the dilution gas to a second set value;
The working gas supply port, the suction port, and the discharge port are connected, and the dilution gas supply line is connected to the working gas supply port, and the reactive gas supply line is connected to the suction port. A vacuum generator that mixes with gas,
A mixed gas supply line provided with a compressor connected to the discharge port of the vacuum generator and pressurizing the mixed gas discharged from the discharge port;
And the outlet side of the mixed gas supply line is the point of use.   The mixed gas supply system according to claim 1, further comprising a reactive gas heating device that heats the reactive gas supply line that reaches at least an inlet of the first mass flow control device.   3. The mixed gas supply system according to claim 1, wherein the reactive gas is hydrogen fluoride or chlorine trifluoride, and the diluent gas is argon, nitrogen, or helium.

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