JP2000249298A - Gas supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a unit valve capable of efficiently performing gas replacement. SOLUTION: This gas supply apparatus repeats a designated number of times a pressurizing and charging process of releasing process gas in passages 11, 14 and a chamber 1 to the air to be discharged, and then pressurizing the purge gas to be charged in the passages 11, 12, 14 and the chamber 1, and a normal pressure exhaust process of releasing the mixed gas of process gas and purge gas charged at high pressure in the passages 11, 14 and the chamber to the air to be discharged by controlling valves 3A, 5A, 6A... piped in each of the process gas passage 11 and the purge gas passage 14 and air release valves 8, 10 piped in the exhaust part by a drive control means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve unit used in an industrial manufacturing apparatus such as a semiconductor manufacturing apparatus.
More specifically, the present invention relates to a valve unit capable of efficiently replacing a residual gas in a flow path or the like.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, a process gas such as a corrosive gas, a toxic gas, or a flammable gas has been conventionally used as a supply gas for etching of a photoresist process or the like. Photoresist processing (photoresist coating, exposure,
Development and etching) are repeated a plurality of times in the semiconductor manufacturing process, and a gas supply system that supplies a process gas as needed is used therein. That is, in the photoresist processing, a plurality of types of process gases, or process gases having the same type but different concentrations may be used. Therefore, in a chamber constituting a closed space, a plurality of process gases such as corrosive gases and component gases are mixed, or an inert gas is mixed with the process gas or the like to obtain a predetermined concentration. Supplied.

However, among the process gases, the corrosive gas, if left in the pipe after being supplied, corrodes the metal and the like inside the pipe. Was adversely affected. If a small amount of the corrosive gas remains, the components of the process gas to be used next change, which has a significant adverse effect on photoresist processing and causes deterioration in the quality of semiconductor products. Furthermore, if the process gas used last time is a flammable gas or the like, even if the remaining amount is a small amount, it may be mixed with the next gas depending on the type, and combustion or explosion may occur due to the flammable gas. Was. Therefore, in the gas supply system, a plurality of types of predetermined amounts of process gases are mixed in a chamber to produce a supply gas, which is supplied to a semiconductor process. Gas) is replaced with an inert gas (purge gas) such as nitrogen gas.

Conventional replacement methods include:
(1) A method in which the residual gas in the flow path is suctioned and evacuated by forced evacuation means such as a vacuum pump and an ejector, and then the supply of the purge gas into the flow path and the suction and evacuation by the ejector are repeated. There is known a method in which an inert gas is introduced into a flow path and the remaining process gas is diluted and discharged.

[0005]

However, in the above method (1), in the case of a vacuum pump, the vacuum pump is located away from the chamber and the like due to maintenance management and space problems, so that the inside of the chamber and the like can be efficiently arranged. At the same time, the gas cannot be evacuated, and at the same time, the corrosive gas, which is one of the supply gases, has strong adhesion to the metal. Could not be eliminated. Since the vacuum pump is arranged at a remote position, the vacuum pump is connected to a chamber or the like in which a corrosive gas or the like remains inside by a pipe. For this reason, the elongation of the piping increases the exhaust resistance, which prevents the inside of the chamber or the like from being evacuated, and the remaining supply gas cannot be completely eliminated.

On the other hand, when an ejector is used for suction and exhaust, an inert gas as a working fluid is blown out at a high flow rate, and a process gas remaining at a negative pressure generated by the rapid flow of the inert gas is removed. Since the gas is sucked and discharged, the consumption of the inert gas (purge gas is used) increases, and the economical downside is large. On the other hand, the method (2) has a problem that it takes too much time to dilute the remaining process gas. That is, since a dead space is created in the flow path, which causes stagnation, the flow there is poor, and the time required for dilution to a tentative reference value has been long.

Therefore, an object of the present invention is to provide a unit valve capable of efficiently performing gas replacement in order to solve the above-mentioned problems.

[0008]

According to the present invention, there is provided a gas supply apparatus comprising: a valve and a mass flow controller for controlling a flow of a process gas provided in a process gas flow path for supplying a process gas to a chamber; A valve for controlling a flow of a purge gas connected to the process gas flow path and a purge gas flow path for supplying a purge gas into the chamber, and a flow path connected to an exhaust portion of the chamber and the purge gas flow path. An air release valve for discharging gas in a passage and a chamber under atmospheric pressure, and drive control means for driving and controlling each of the valves and the mass flow controller; Is a valve that is piped to each of the process gas flow path and the purge gas flow path, and a large pipe that is piped to the exhaust part. By controlling the release valve, after the process gas in the flow path and the chamber is released to the atmosphere and exhausted, a pressurizing and sealing step of pressurizing and sealing a purge gas in the flow path and the chamber; A normal pressure exhaust step of releasing a mixed gas of a process gas and a purge gas filled in the chamber at a high pressure to the atmosphere and exhausting the mixed gas is repeated a predetermined number of times.

Therefore, according to the gas supply device of the present invention,
In the gas replacement after the process gas is mixed in the chamber and the gas is supplied, a predetermined cycle purge is performed by the drive control unit. That is, since the process gas remains filled in the process gas flow path and the chamber at a predetermined pressure in the previous step, the process gas is once released to the atmosphere and exhausted, and the pressure in the flow path and the chamber is reduced. Reduce to atmospheric pressure. Thereafter, in a pressurizing and sealing step, a purge gas is pressurized and sealed, and a mixed gas of a process gas and a purge gas is filled into the flow path and the chamber at a high pressure. The mixed gas filled is exhausted by a pressure difference from the atmospheric pressure, thereby diluting the process gas remaining in the flow path and the chamber.
Then, by repeating the pressurizing sealing step and the normal pressure exhausting step a predetermined number of times, the concentration of the process gas remaining in the flow path and the chamber is reduced to a predetermined value. Therefore, by performing such a cycle purge of the normal pressure exhaust, a forced exhaust unit such as an ejector or a vacuum pump is not required, and the configuration of the gas supply system can be simplified. The problem of an ejector that consumes a large amount of purge gas is solved. In addition, since the evacuation time is short according to the normal pressure evacuation, the time required for gas replacement can be shortened even if the number of repetitions increases.

Further, in the gas supply system according to the present invention, the drive control means determines the number of repetitions of the pressurizing / enclosing step and the normal-pressure exhausting step based on the filling pressure of the purge gas filled in the pressurizing / enclosing step. It has a control program. As a result, the process gas remaining in the flow path and the chamber can be accurately diluted to a desired concentration, and the time required for gas replacement can be reduced by performing a necessary and sufficient number of repetitions. . Further, the gas supply system according to the present invention is characterized in that a bypass flow path connecting one side and a secondary side of the mass flow controller provided in the process gas flow path is provided. As a result, the pressurized filling of the purge gas and the exhaust of the mixed gas are efficiently performed without being hindered by the mass flow controller, which contributes to shortening of the time required for gas replacement.

[0011]

Next, an embodiment of a gas supply system embodying the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of the gas supply system. This gas supply system is for supplying a predetermined gas to an etching processing apparatus or the like in a semiconductor manufacturing process, and is configured to supply a plurality of process gases to the chamber 1. In the present embodiment, five types of process gases FA to FE can be transferred to the chamber 1. Therefore, the five process gas flow paths 11A to 11E that transport the five types of process gases FA to FE to the hollow portion 1a of the chamber 1 include mass flow controllers 2A to 2E that adjust the flow rates of the process gases FA to FE. Gas carry-in valves 3A to 3E for controlling carry-in of the flow-controlled process gases FA to FE into the chamber 1 are connected in series, respectively. Further, on the upstream side of the process gas flow paths 11A to 11E, a gas supply valve 5 for controlling the flow of the process gases FA to FE from the gas supply source is provided.
A to 5E are connected in series.

The gas supply system is configured to replace the process gas remaining in the chamber 1 and the flow path. An inert gas such as a nitrogen gas is used as a purge gas at the time of gas replacement. The purge gas is configured to be supplied from the gas supply source through the purge gas supply path 12 to each of the process gas flow paths 11A to 11E, and exhausted through the purge gas discharge path 13. That is, the purge gas supply path 12 and the purge gas discharge path 13 are connected via the connection flow paths 14A to 14E in which the gas replacement valves 6A to 6B and the exhaust valves 7A to 7B are piped. And
The gas replacement valves 6A to 6B and the exhaust valves 7A to 7B
The process gas flow paths 11A to 11E merge with the connection flow paths 14A to 14E. Purge gas discharge path 13
An air release valve 8 is provided in front of a collection container (not shown) for discharging residual gas. The purge gas supply path 12, the purge gas discharge path 13, and the connection flow path 14
A to 14E correspond to the purge gas flow path described in claim 1. Further, the chamber 1 has gas discharge valves 9F to 9H in a discharge path for discharging the mixed process gas to three directions.
And an atmosphere release valve 10 is provided in front of a collection container (not shown) for discharging the residual gas. In addition, an electromagnetic valve is used for each valve constituting the gas supply system.

The gas supply system is controlled by a control device shown in FIG. The control device 20 includes a CPU 21 for controlling the entire system, a ROM 22 storing a control program for controlling supply of a process gas and supply and exhaust of a purge gas of a supply gas system, and a CPU 21.
Is provided with a RAM 23 for temporarily storing data and the like when performing arithmetic processing, and for storing data input from the outside. The CPU 22 includes the valves 3A to 3A.
3E, 5A to 5E, 6A to 6E, 7A to 7E, 8, 9G
Valve control unit 2 for executing opening and closing of ， 9H, 10
4 and a flow controller 25 for controlling the driving of the mass flow controllers 2A to 2E.

The operation of the gas supply system will now be described. The gas supply system uses the R
This is executed according to the control program stored in the OM 22. First, five types of process gases FA to F are input by a command from a computer that controls the entire semiconductor manufacturing process.
When one or more gases are selected from E, the gas supply valves 5A to 5E corresponding to the selected process gases FA to FE are opened. Selected process gas FA
FE flow through the process gas flow paths 11A to 11E to the mass flow controllers 2A to 2E, respectively. Since the corresponding gas carry-in valves 3A to 3E are also opened by the control command, the mass flow controllers 2A to 2E
The flow rates of the process gases FA to FE are adjusted by E and supplied to the chamber 1. On the other hand, on the output side of the chamber 1, only the gas discharge valves 9F to 9H connected to the supply destination are opened. Hollow part 1 of chamber 1
Since gas flows into a at a high flow rate, the gas is sufficiently mixed without attaching a special mixing device to the hollow portion 1a, and is output from the open gas discharge valves 9F to 9H. Then, the mixed process gas is supplied to an etching apparatus or the like in a semiconductor manufacturing process.

When the supply flow rates of the process gases FA to FE reach predetermined values, the gas carry-in valves 3A to 3E and the gas supply valves 5A to 5E are closed, and the gas supply to the chamber 1 is stopped. The value of the supply flow rate that determines the timing for closing the gas carry-in valves 3A to 3E and the gas supply valves 5A to 5E is experimentally determined in consideration of the amount that finally remains in the hollow portion 1a of the chamber 1. And
Gas carry-in valves 3A-3E and gas supply valves 5A-5
Subsequent to the closing of E, the gas discharge valves 9F to 9H are closed. As a result of the opening and closing of each valve as described above, the process gas remains in each of the process gas channels 11A to 11E and the chamber 1, so that gas replacement is performed subsequently.

By the way, as described in the above-mentioned conventional example, the gas replacement is performed by sucking and exhausting a process gas in a flow path by a vacuum pump and an ejector, then supplying a purge gas into the flow path and sucking and exhausting by a vacuum pump and an ejector. repeat,
A method called cycle purging of evacuation (hereinafter, referred to as “vacuum cycle purging”) is generally used. The purpose of forcibly sucking and exhausting the gas using a vacuum pump or the like after supplying the purge gas is to improve the efficiency of exhausting the residual gas in the flow path. And such a method has been performed with common sense. However, from the following, it can be seen that the gas can be sufficiently replaced even by the cycle purge of the normal pressure exhaust (hereinafter, referred to as “normal pressure cycle purge”) in which the high pressure charging of the purge gas and the exhaust by the release to the atmosphere are repeated. Do you get it. The expected results were also obtained from the normal pressure cycle purge test. Therefore, the theory of the normal pressure cycle purge will be described first.

Gas replacement by cycle purge can be performed based on the concept of dilution by pressure ratio. That is,
The concentration of the process gas contained in the space at a certain reference pressure is
The purge gas is diluted according to the ratio of the reference pressure value to the reference pressure value when the pressure of the purge gas is reduced from the raised pressure to the reference pressure by the exhaust gas. Therefore, when vacuum evacuation is performed using an ejector, the ultimate pressure of the vacuum in the flow path is about 1.064 × 10 ⁴ Pa due to the forced evacuation of the ejector, whereas the purge gas sealed in the flow path is about It is assumed that the pressure is 2.969 × 10 ⁵ Pa. Therefore, after the pressure in the flow path is increased by pressurizing and filling the purge gas,
When the pressure is reduced by evacuation by the ejector, the dilution rate by this one cycle purge is 1.06 × 1
Calculated as 0 ⁴ /2.97×10 ⁵ . Therefore, the concentration of the residual gas is diluted to about 1/30 by one cycle purge, and the concentration of the residual gas in the flow path and the like is diluted to (1/30) ⁿ by repeating the cycle purge n times. It will be.

When actually performing gas replacement, it is necessary to dilute the concentration of the residual gas in the flow path to a concentration of, for example, 0.05 ppm or less so as not to adversely affect the next supply gas. It may be a reference value. In order to dilute the concentration of the residual gas to the reference value when performing the vacuum cycle purge by the ejector as described above, (1/30) ⁵ 4.1 × 10 ⁻⁸ (= 0.041 pp)
m), and it is sufficient to repeat five times.

Similarly, the case of normal pressure cycle purge will be considered. Assuming that the atmospheric pressure is about 1.01 × 10 ⁵ Pa and the purge gas sealed in the flow path is about 2.97 × 10 ⁵ Pa, the residual gas in the flow path is removed by one cycle purge. The dilution ratio is 1.01 × 10 ⁵ /2.97×10
Calculated by ⁵ . Therefore, the concentration of the residual gas is diluted to about 1/3 by one cycle purge. If the cycle purge is repeated n times, the concentration of the residual gas in the flow path becomes (1/1).
30) ^Will be diluted to ⁿ . Therefore, in order to dilute the concentration of the residual gas to the reference value, it becomes (1/3) ¹⁶ 2.3 × 10 ⁻⁸ (= 0.023 ppm), and it is sufficient to repeat 16 times. Therefore, if the cycle purge is performed 16 times, which was performed theoretically 5 times when the ejector is used, the process gas can be supplied without leaving the influence of the residual gas in the flow path next. .

Based on this idea, the gas supply system according to the present embodiment adopts the normal pressure cycle purge, and is implemented as follows. As described above, after the supply of the predetermined process gases FA to FE is finished, first, (1) the exhaust valves 7A to 7 which are piped to the atmosphere release valves 8 and 10 and the corresponding process gas channels 11A to 11E.
B can be opened. Then, the process gas flow paths 11A-1A
The process gas filled in the chamber 1E and the chamber 1 at a predetermined pressure is exhausted. However, the flow of the residual gas is small, and the residual gas remains at the atmospheric pressure in the process gas flow paths 11A to 11E and the chamber 1, so that the normal pressure cycle purge is subsequently performed.

(2) After the atmosphere release valves 8 and 10 are once closed, the corresponding gas replacement valves 6A to 6B are opened and the purge gas is pressurized and sealed. Therefore, the process gas flow paths 11A to 11E and the inside of the chamber 1 are filled with the residual gas and the purge gas at a pressure of about 2.97 × 10 ⁵ Pa. Thereafter, (3) the corresponding gas replacement valves 6A to 6B are closed and the atmosphere release valves 8, 10 are opened. Thereby, the process gas flow paths 11A to 11A
E and the high-pressure gas in the chamber 1 are exhausted from the atmosphere release valves 8 and 10 vigorously. Thereby, the residual gas in the process gas flow paths 11A to 11E and the chamber 1 is diluted to about 1/3 based on the above-described theory. Thereafter, the operations of (2) and (3) are repeated a predetermined number of times n
By repeating, the process gas flow paths 11A to 11A
E and the concentration of the residual gas in the chamber 1 are about (1/3)
^It can be diluted by ^{n to} below the desired reference value.

Here, the results of tests performed on the normal pressure cycle purge performed in the gas supply system of the present embodiment and the conventional vacuum cycle purge will be compared. FIG.
FIG. 4 and FIG. 4 are graphs showing test results on gas replacement characteristics. In this test, gas replacement was performed by purging with nitrogen gas in a flow path filled with oxygen instead of corrosive gas. The graph of FIG. 3 shows a comparison of the purge time with respect to the residual oxygen concentration in the flow channel.
In the graph, the comparison of the nitrogen gas consumption with respect to the residual oxygen concentration in the flow path is shown.

Therefore, a comparison is made between the purge time until the oxygen concentration reaches a predetermined reference value and the nitrogen gas consumption by the normal pressure cycle purge (indicated by a solid line) and the vacuum cycle purge (indicated by a dashed line). As shown in FIG. 3, the time required for diluting the oxygen concentration to about 0.05 ppm has almost no difference between the two, and the normal pressure cycle purge has an extra time of about 10 seconds. It only needed. On the other hand, as shown in FIG. 4, as for the nitrogen gas consumption, the consumption of the nitrogen gas used for the gas replacement was much larger in the vacuum cycle purge than in comparison.

As can be seen from the results, the time required for the dilution hardly differs between the two, because the time required for one evacuation is longer than the normal pressure evacuation. That is, when the concentration of the residual gas is diluted to the reference value, the normal pressure cycle purge is only six times while the normal pressure cycle purge is sixteen times from the above calculation example. Should be about 1/3 of However, according to the test, while it took about 10 seconds for the ejector to suction and exhaust the inside of the flow path to the ultimate pressure, it was not possible to release the air to the atmosphere and bring the inside of the flow path to atmospheric pressure. It took about 2 seconds. Therefore, the normal-pressure cycle purge requires much less time for one cycle.
As shown in FIG. 3, there was almost no difference. On the other hand, the result shown in FIG. 4 is that in the case of the normal pressure cycle purge, only the amount of the nitrogen gas pressurized and sealed in the flow path as the purge gas, that is, only the inclusion body integral is consumed, This is because, in the case of vacuum cycle purging, nitrogen gas is used as a working fluid for the ejector, and the amount of consumption for that is significantly large.

Therefore, according to the gas supply system of the present embodiment, the gas replacement in the flow path and the like is performed by the normal pressure cycle purge, so that the difference in the time required for the gas replacement is reduced as compared with the vacuum cycle purge. However, the purge gas consumption was significantly reduced. In addition, since there is no need to provide equipment such as an ejector for forcibly exhausting and exhausting gas in the flow path and piping, the configuration of the gas supply system is simplified, and the equipment cost is thereby reduced. Also, R
In the control program stored in the OM 22, the number of repetitions of the normal pressure cycle purge is set by the pressure of the purge gas, so that the process gas remaining in the flow path and the chamber can be accurately diluted to a desired concentration. By performing the necessary and sufficient number of repetitions, the time required for gas replacement can be shortened.

By the way, in the gas supply system, the mass flow controllers 2A to 2E are factors that hinder the filling of the purge gas and the exhaustion of the mixed gas at the time of gas replacement. These are the mass flow controllers 2A to 2E
Is as small as about 1/10 of the valve. Therefore, it is desired to eliminate the influence of the mass flow controller and to more effectively fill the purge gas and exhaust the mixed gas. Therefore, a bypass flow path as shown in FIG. 5 is configured in the gas supply system shown in FIG. FIG.
FIG. 3 is a circuit diagram showing a part of the gas supply system. That is, the gas supply valves 5 (5A to 5E), the mass flow controllers 2 (2A to 2E), and the gas carry-in valves 3 (3A) are provided in the process gas flow paths 11 (11A to 11E).
To 3E), and a connection flow path 14 (14A) from a purge gas supply path 12 that joins the process gas flow path 11.
To 14E), gas replacement valves 6 (6A to 6E) are piped. Therefore, the bypass flow path 31 is connected to the connection flow path 14 on the secondary side of the gas replacement valve 6 which is the primary side of the mass flow controller 2 and the process gas flow path 11 on the secondary side of the mass flow controller 2 as shown in the figure. Connected.
The bypass flow path 31 is provided with a bypass valve 32.

The bypass flow path 31 is shut off when the process gas is supplied by closing the bypass valve 32, and communicates by opening the bypass valve 32 when replacing the gas. Thereby, at the time of gas replacement, the gas bypassing the mass flow controller 2 is supplied to the bypass passage 31.
Therefore, the filling of the purge gas and the exhaust of the mixed gas can be performed without being affected by the mass flow controller 2. Accordingly, the time for filling the purge gas and the time for exhausting the mixed gas are reduced, and the total time required for gas replacement in the normal pressure cycle purge is reduced.

The present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention. For example, the configuration of the gas supply device shown in FIG. 1 is an example, and there is no problem even if another layout is adopted. In addition, it goes without saying that the charging pressure of the process gas, the number of repetitions of the purge, and the like are changed depending on the process gas used.

[0029]

According to the present invention, in the case of gas replacement, the drive control means controls a valve provided in each of the process gas flow path and the purge gas flow path and an atmosphere release valve provided in the exhaust part. Then, after the process gas in the flow path and the chamber is released to the atmosphere and exhausted, a pressure sealing step of pressurizing and sealing the purge gas in the flow path and the chamber, and the flow path and the chamber are filled with a high pressure. Since the normal pressure exhausting step of releasing the mixed gas of the process gas and the purge gas to the atmosphere and exhausting the same is repeated a predetermined number of times, it is possible to provide a unit valve capable of efficiently replacing the process gas. Was.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an example of a configuration of a gas supply system according to the present invention.

FIG. 2 is a block diagram illustrating an example of a control device of the gas supply system according to the present invention.

FIG. 3 is a diagram showing gas replacement characteristics with respect to a purge time.

FIG. 4 is a diagram showing gas replacement characteristics with respect to purge gas consumption.

FIG. 5 is a circuit diagram showing a part of the gas supply system shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 chamber 2A-2E mass flow controller 3A-3E gas carry-in valve 5A-5E gas supply valve 6A-6E gas replacement valve 8,10 atmosphere release valve 11,11A-11E process gas flow path 12 purge gas supply path 13 purge gas discharge path 14, 14A to 14E Connecting flow path 21 CPU 22 ROM 23 RAM 24 Valve control unit

Claims (3)

[Claims] 1. A valve and a mass flow controller for controlling a flow of a process gas provided in a process gas flow path for supplying a process gas to a chamber; A valve for controlling a flow of a purge gas provided in a purge gas flow path for supplying a purge gas into the chamber, and a gas provided in an exhaust portion of the chamber and the purge gas flow path for controlling a gas in the flow path and the chamber under atmospheric pressure. And a drive control unit for driving and controlling each of the valves and the mass flow controller. In the case of gas replacement, the drive control unit includes the process gas passage and the purge gas passage. By controlling a valve piped to each flow path and an atmosphere release valve piped to the exhaust part, After the process gas in the flow path and the chamber is released to the atmosphere and exhausted, a pressurizing sealing step of pressurizing and sealing a purge gas in the flow path and the chamber; and a process gas filled in the flow path and the chamber at a high pressure. A normal pressure exhausting step of releasing a mixed gas of a gas and a purge gas to the atmosphere and exhausting the gas to the atmosphere a predetermined number of times. 2. The gas supply system according to claim 1, wherein the drive control unit is configured to repeat the pressurizing / enclosing step and the normal-pressure exhausting step in accordance with a sealing pressure of a purge gas sealed in the pressurizing / enclosing step. A gas supply system comprising a control program for determining a gas supply. 3. The gas supply system according to claim 1, wherein a bypass flow path connecting one side and a secondary side of the mass flow controller provided in the process gas flow path is provided. And gas supply system.