JP2937272B2 - Supply / exhaust gas switching system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for switching between supply and exhaust gas.

[0002]

2. Description of the Related Art Generally, various processing gases are used in a semiconductor manufacturing process. When two or more types of processing gases including air (oxygen) are mixed in these processing gases, they explode or spontaneously explode. Even if it does not explode, there is a possibility that it may explode by ignition. For example, nitrogen fluoride (N
A mixture of F ₃ ) gas and a silane-based gas used for film formation on a semiconductor wafer does not spontaneously explode. However, if there is a fire, there is a risk of explosion due to ignition. In addition, when the silane-based gas is mixed (burned) with the atmosphere (oxygen) for some reason and burned (exploded) at the same time as the nitrogen fluoride gas is mixed therein, the burning power (explosive power) is greatly increased. . Therefore, for example, mixing of a nitrogen fluoride gas and a silane-based gas must be avoided under reduced pressure in a reaction vessel or the like, or under atmospheric pressure such as an exhaust port of a pump.

For this reason, in a conventional supply / exhaust gas switching system for a reaction vessel, when, for example, nitrogen fluoride gas is supplied as a supporting gas by computer control, only a supply valve of a supply line for this gas is opened. On the other hand, in the exhaust system, only the exhaust valve of the exhaust line for the supporting gas is opened to allow the exhaust gas to flow to the exhaust duct dedicated to the supporting gas, and the processing gas containing, for example, a silane-based gas as the combustible gas. When supplying the process gas, contrary to the above, only the supply valve of the supply line of these processing gases is opened, while in the exhaust system, only the discharge valve of the exhaust line of the flammable gas that discharges the processing gas is opened, It is controlled so that it flows to the exhaust duct dedicated to combustible gas, and a certain level of safety is ensured by preventing gas from mixing in the reaction vessel and the exhaust system. Sex is maintained.

[0004]

However, since these gases are very dangerous when mixed as described above, the supply valve and the discharge valve may malfunction even if the control device is in any situation. Although it should not be done, for example, in the event of a sudden power failure, the computer may issue an incorrect command, which may result in the mixing of dangerous gases. there were. The present invention has been devised in view of the above problems and effectively solving them. An object of the present invention is to provide a supply / exhaust gas switching system in which a supply valve can be switched based on a state of a discharge valve.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to supply two or more kinds of gases which must not be mixed to a gas use section via a supply valve, respectively. In a gas use system that discharges exhaust gas from a part to a different exhaust system according to a supply gas through a discharge valve, the supply valve and the discharge valve are changed according to a gas required in the gas use part. A control means for switching, and an interlock mechanism for determining whether or not to switch the supply valve based on a state of the discharge valve regardless of a command from the control means.

[0006]

Since the present invention is constructed as described above, a discharge valve which is normally opened according to the kind of gas supplied to the gas use section is selected by the operation of the control means, and an appropriate exhaust gas is selected. Exhaust gas is discharged to the system. Here, if the control means issues an erroneous command for some reason, regardless of this command, whether or not the supply valve can be switched is determined by the interlock mechanism based on the state of the discharge valve. The operation of the supply valve and the discharge valve in such a direction that the dangerous gas is mixed is prevented.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a system for switching between supply and exhaust gas according to the present invention will be described below in detail with reference to the accompanying drawings. As shown in the drawing, a load lock chamber 4 is connected to a reaction vessel 2 which is a gas use part of a cold wall CVD apparatus via a gate valve 6, and semiconductor wafers carried in / out via the load lock chamber 4. A film forming process or the like is performed on the object to be processed under a predetermined pressure, a predetermined temperature, and a predetermined processing gas atmosphere. In addition, the reaction vessel 2 is provided with a susceptor 10 for heating the semiconductor wafer by the high frequency power supply 8 while holding the semiconductor wafer. The reaction vessel 2 has a supply system 12 for supplying a processing gas or the like thereto.
And an exhaust system 14 for discharging the treated gas or residual gas in the reaction vessel 2. In the present embodiment, for example, a case in which a thin film of a compound of tungsten and silicon is formed will be described. Therefore, the supply system 12 includes a tungsten fluoride (WF ₆ ) supply line 12.
a, a silane (SiH ₄ ) supply line 12b, an argon (Ar) supply line 12c as a diluting gas, and a fluorine gas supply line 12d for supplying an etching gas used during the etching process, for example, nitrogen fluoride. In FIG. 2, an argon supply line is omitted for simplification of the description.

Each supply line has a flow controller 14a, 14b, 14c, 14d and a supply valve 16
a, 16b, 16c and 16d are interposed. on the other hand,
After passing through an exhaust pump 18, the exhaust system 14 is branched into a combustible line 20 through which a combustible gas such as silane, tungsten fluoride, and argon flows, and a combustion support line 22 through which a support gas such as nitrogen fluoride flows. Each of the lines is connected to a combustible duct 24 and a supporting duct 26, and the exhaust gas is rendered harmless by an abatement device (not shown). Each of the combustible line 20 and the combustion support line 22 has a discharge valve 2
Check valves 30a and 30b are provided to prevent the exhaust gas from flowing back to both sides when the two discharge valves 28a and 28b are simultaneously opened. The gas use system configured as described above is provided with the supply / exhaust gas switching system according to the present invention. The switching system includes a control means 32 for switching the supply valves 16a, 16b, 16c, 16d and the discharge valves 28a, 28b according to the gas required in the reaction vessel 2,
Regardless of the command from the control means 32, the supply valves 16a, 1
6b, 16c, and 16d. The control unit 32 includes a main processing unit 32a in which processing conditions (temperature, pressure, time, etc.) of a semiconductor wafer, a valve switching command, and the like are input in advance and a control unit that issues an opening / closing operation command to each valve. 32b and the discharge valves 28a, 28b
And a switching pneumatic circuit section 32c that switches between the two.

The switching pneumatic circuit section 32c has a delay section 38 composed of a mechanical valve operated by a compressed gas. The delay unit 38 is provided with the combustible delay unit 3.
8a and a support delay section 38b.
8a and 38b are driving air sources 40a and 40b, respectively.
These are connected in series with throttle valves 42a and 42b, respectively, to which check valves for backflow prevention are connected in parallel, and air tanks 44a and 44b for generating a delay time of 30 seconds, for example. The outputs of the air tanks are output from delay valves 46a and 46
b, so that the cylinder in the valve can be switched when the air pressure reaches a predetermined pressure. The output port of the combustible delay valve 46a is connected to the open side of the combustible cylinder 50a that drives the valve element of the combustible discharge valve 28a and the combustion support side that drives the valve element of the combustion support side discharge valve 28b. It is connected to the closed side of the cylinder 50b. On the other hand, the output port of the support delay valve 46b is connected to the open side of the support cylinder 50b and the close side of the combustible cylinder 50a, and air is supplied into any of the cylinders. Also, the pistons 52a and 52b in the cylinders 50a and 50b are configured to operate in opposite directions like a seesaw. The pistons 52a and 52b are connected to drive shafts 54a and 54b for opening and closing valve bodies (not shown) of the discharge valves 28a and 28b, respectively, and open / close positions of the drive shafts 54a and 54b. Is detected by an open / closed state detection valve described later. In the illustrated example, the combustible discharge valve 28a is open, and the combustion supporting discharge valve 28b is closed.

On the other hand, the interlock mechanism 34 comprises a compressed gas, for example, compressed air, and a number of mechanical valves operated by the compressed gas. In particular,
The interlock mechanism 34 is provided with the flammable discharge valve 2.
Combustible open state detecting valve 56a and combustible closed state detecting valve 56b for detecting the open state and closed state of 8a, respectively.
And a combustion support open state detection valve 58a and a fuel support closed state detection valve 58b that detect the open state and the closed state of the combustion support discharge valve 28b, respectively. It is configured to be mechanically movable by drive shafts 54a, 54b attached to the valve bodies of the discharge valves 28a, 28b. The output port of the combustion support closed state detection valve 58b is connected to the input port of the combustible open state detection valve 56a.
The output port 6a is connected to the air signal 62 via the monitoring unit 60.
It is sent to the supply system 12 side as a. That is, the air signal 62a is ANDed between the valve 58b and the valve 56a, and is output when the fuel discharge valve 28b is closed and the combustible discharge valve 28a is open.

On the other hand, the flammable closed state detection valve 56b
The output port is connected to the input port of the open state detection valve for combustion 58a, and the output port of the valve 58a is sent to the supply system 12 as the air signal 62b via the monitoring unit 60. That is, the air signal 62b is ANDed between the valve 56b and the valve 58a, and is output when the combustible discharge valve 28a is closed and the combustion supporting discharge valve 28a is open. Each supply valve 16a, 16b, 16 of the supply system 12
c and 16d include interlock valves 66a and 66b for shutting off the supply of the driving compressed air for opening and closing.
66c and 66d (66c is omitted) are provided. The input ports of these valves 66 are connected to a drive compressed air source (not shown) for opening / closing commands supplied under the control of the control means 32, and the output ports are connected to the corresponding supply valves 16. The opening and closing command signal and the air signal 62 are ANDed to drive the valve element. And, among the interlock valves 66, interlock valves 66 for combustible gas, that is, silane, tungsten fluoride, and argon are used.
The air signal 62a is supplied to each cylinder side of the cylinders a, 66b, 66c, and 66c (not shown).
When a is open and the fuel discharge valve 28b is closed, the cylinder can be operated in the opening direction.

The air signal 62b is supplied to the cylinder side of an interlock valve 66d for a combustion supporting gas, that is, nitrogen fluoride.
b, that is, the cylinder can be operated in the opening direction when the combustible discharge valve 28a is closed and the combustion supporting discharge valve 28b is opened. The monitoring unit 60 performs matching between a signal output from the computer of the control means 32 and the actual opening / closing state of each of the discharge valves 28a and 28b. It is made as shown. Further, the combustible duct 24 and the support duct 26 are provided with a plurality of gas use systems having the same configuration as described above.

Next, the operation of this embodiment configured as described above will be described. First, the main processing device 32a of the control means 32 supplies processing contents, for example, processing temperature, processing pressure, processing time, processing gas to be supplied and its flow rate, corresponding opening / closing command of the supply valve 16 and the discharge valve 28, and A cleaning operation and the like are programmed and stored in advance as a recipe, and various controls are performed based on the program. A semiconductor wafer (not shown) is carried into the load lock chamber 4, and the inside thereof and the inside of the reaction vessel 2 are also evacuated to a predetermined pressure. Thereafter, the exhaust pump 18 always operates to exhaust air. Then, the semiconductor wafer is accommodated in the reaction vessel 2 via the gate valve 6, and the gate valve 6 is closed. Then, the semiconductor wafer is heated and maintained at a predetermined temperature by the high-frequency power supply 8, and tungsten fluoride, silane, and argon are flown as combustible gases into the reaction vessel 2, and a film forming process is performed at a predetermined pressure and a predetermined temperature for a predetermined time. It is.

In the meantime, the cylinders of the interlock valves 66a, 66b, 66c for supporting gas are, of course, located above the illustrated example, and the corresponding supply valves 16a, 16b, 16c are opened by driving compressed air. The interlock valve 66 for combustible gas
Since d is located below the illustrated example and the drive compressed air is not supplied unless a failure occurs, the supply valve 16d is in a closed state, and the supply of nitrogen fluoride is completely shut off. On the other hand, in the exhaust system 14, the flammable cylinder 5
0a and the pistons 52a, 5a of the combustion supporting cylinder 50b.
2b is located as shown in FIG.
a is opened and the combustion supporting discharge valve 28b is closed,
The exhaust gas is discharged to a combustible duct 24. When the film forming process is completed in this way, the supply of the processing gas is stopped, the gate valve 6 is opened, and the processed semiconductor wafer is carried out to the load lock chamber. And the same processing as described above is repeated. In this way, processing of a predetermined number of sheets, for example, 25 or 100 sheets is performed. During this time, the supply system and the exhaust system on the combustible side are always used. When a predetermined number of processes have been completed, the process moves to a cleaning operation for removing the film adhering to the inside of the reaction vessel 2.

First, the main processing unit 32a includes the exhaust system 1
The control unit 32b outputs a signal for supplying the drive air 40b to the delay valve 46b of the fuel-supply delay unit 38b, and outputs the signal to supply the drive air 40b to the delay valve 46b of the fuel-supply delay unit 38b. A signal for opening the drive air 40a of the delay valve 46a at 38a is output. in this case,
A semi-automatic operation may be adopted, the operator confirms a command from the main processing unit 32a, and the operator may manually input a switch for performing the valve operation. In this way, even when the driving air 40b is supplied, the discharge valve 28b does not open immediately. That is,
The flow rate of the drive air 40b is reduced by the throttle valve 42b and gradually stored in the air tongue 44b.
After a lapse of a predetermined time, for example, 30 seconds, after the start of the supply, a certain pressure is reached and the cylinder of the delay valve 46b is pushed down. That is, by the function of the delay valve 46b, a delay operation of, for example, 30 seconds is performed, and during this time, the combustible gas remaining in the reaction vessel 2 and the exhaust system is reliably discharged to the outside. Become. The delay time of 30 seconds can of course be set arbitrarily.

When the cylinder of the delay valve 46b moves downward after the elapse of the delay time of 30 seconds, the compressed air from this output port moves the piston 52b of the combustion supporting cylinder 50b in the open direction. To move the piston 52a of the combustible cylinder 50a in the closing direction at the same time.
a, thereby opening the supporting-side exhaust valve 28b and closing the combustible-side exhaust valve 28a. That is, the pistons 52a and 52b of the respective cylinders are in a state opposite to the illustrated side. Then, by the action of each of the drive shafts 54a and 54b, the state of the cylinder of the open state detection valve 56b on the combustible side is reversed from that shown in the figure, and at the same time, the state of the cylinder of the open state detection valve 58a and the closed state detection valve 58b on the combustion support side. The state is reversed from the illustrated side. Therefore, the air signal 62a that has been supplied through the combustion supporting closed state detection valve 58b and the flammable open state detecting valve 56a is no longer released. In contrast, the flammable closed state detecting valve 56b and the fuel supporting Air signal 62b through the use open state detection valve 58a
Is sent to the supply system 12.

Therefore, the cylinder of the interlock valve 66d which has received the air signal 62b is pushed upward to enable the supply of the driving compressed air to the combustion support system, that is, the supply valve 16d of the nitrogen fluoride. Since the previous air signal 62a has been extinguished, the other combustible interlock valves 66a, 66b, 66c are depressed, and supply of the drive compressed air to the supply valves 16a, 16b, 16c is not possible. Making it possible. On the other hand, an air signal 62b indicating that the combustion supporting side discharge valve 28b is open and the combustible side discharge valve 28a is closed.
Is transmitted also to the control unit 32b side (the transmission path is not shown), and upon receiving this signal, the main processing device 32a issues a supply instruction of nitrogen fluoride to perform a cleaning process,
The corresponding drive compressed air is supplied to the supply valve 16d. At this time, as described above, the cylinder of the interlock valve 66d is pushed upward, and the driving compressed air is in a flowable state.
6d is immediately opened, nitrogen fluoride is supplied into the reaction vessel 2, and the cleaning process is performed under a predetermined condition, for example, N 2.
F ₃ of the flow rate 300SCCM, pressure 300mmTorr,
This is performed in a high-frequency power of 300 W and a processing time of 20 minutes. As described above, the exhaust gas at this time is supplied to the combustion support line 22 because only the discharge valve 28b of the combustion support system is open.
Through the support duct 26. Therefore, the combustion supporting gas does not mix with the combustible gas.

When the cleaning process for a predetermined time is completed in this way, the supply of nitrogen fluoride is stopped, the same delay operation as described above is performed, and the process returns to the normal semiconductor processing process. Will go. Here, for example, in a state where a combustible gas such as silane is supplied to process a semiconductor wafer as shown in the drawing, the control means 32 erroneously supplies nitrogen fluoride as a support gas due to some error. Assume that a power signal is output. When this signal is output, the drive compressed air is supplied to the corresponding supply valve 16d. However, the cylinder of the corresponding interlock valve 66d is kept down by the operation of the interlock mechanism 34. The supply of air to the supply valve 16d is shut off, and the supply valve 16d is shut off.
d does not work at all. That is, the supply valve 16d is not opened unless at least the air signal 62d indicating that the combustion supporting discharge valve 28b is open and the combustible discharging valve 28a is closed is output.

Therefore, the control means 32 prevents the supply of the supporting gas by the operation of the interlock mechanism 34 even if it issues a command for supplying the supporting gas by mistake. It is possible to reliably prevent the gas and the supporting gas from being mixed. Even if a cleaning operation command is erroneously output during processing of a semiconductor wafer, the discharge valves 28a and 28b are not operated for 30 seconds after the command is issued by the above-described 30-second delay operation. Instead, the discharge valves 28a and 28b are switched after 30 seconds have elapsed. Therefore, even if a cleaning gas (nitrogen fluoride) is subsequently introduced, the previous 30
Since flammable gas is discharged out of the system every second,
There is no risk that these gases will mix. As described above, in the present embodiment, the interlock mechanism is configured not by electrical control but by mechanical control that is safe and secure using a mechanical valve, so that the interlock function can be reliably executed. it can.

Even if the command is issued by mistake, a delay of a predetermined time, for example, 30 seconds, always occurs after the command is issued, so that the combustible gas and the supporting gas are mixed in the reaction vessel or in the exhaust system. This can be reliably prevented. still,
At the time of gas discharge, each gas is actually safer because each gas is sufficiently diluted to the explosion limit by N ₂ gas. Further, in the above embodiment, the case where the present invention is applied to a CVD apparatus has been described. However, the present invention is not limited to this. Of course, it is also applicable. Further, the interlock mechanism may be constituted by an electric circuit instead of the compressed air. Furthermore, in the above embodiment, two types of gas, that is, the supporting gas and the flammable gas, have been described. However, the present invention is not limited to this, and three or more types of gas that must not be mixed with each other may be used. Can be applied.

[0021]

As described above, according to the present invention, the following excellent functions and effects can be exhibited. An interlock mechanism is provided to determine whether the supply-side valve can be switched based on the state of the discharge-side valve. Therefore, even if the control unit issues an erroneous command due to an error, or the operator issues an erroneous command. In addition, mixing of two or more gases that are dangerous when mixed can be prevented beforehand. Therefore, the safety of the gas use system can be further improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a supply and exhaust gas switching system according to the present invention by CVD
It is a block diagram showing the state applied to the device.

FIG. 2 is a detailed view showing details of an interlock mechanism of the supply / exhaust gas switching system according to the present invention.

[Explanation of symbols]

 2 Reaction vessel (gas use part) 12 Supply system 14 Exhaust system 16a, 16b, 16c, 16d Supply valve 18 Exhaust pump 20 Combustible line 22 Combustion line 24 Combustible duct 26 Combustion duct 28a, 28b Exhaust valve 32 Control means 34 Inter Lock mechanism 38 Delay unit

Claims (3)

(57) [Claims] 1. A method for supplying two or more types of gases which must not be mixed to a gas use part via respective supply valves,
In a gas use system that discharges exhaust gas from the gas use unit to a different exhaust system according to a supply gas via a discharge valve, the supply valve and the exhaust gas may be used according to a gas required in the gas use unit. Control means for switching between the valve and, regardless of a command from the control means,
A supply / exhaust gas switching system, comprising: an interlock mechanism for determining whether or not the supply valve can be switched based on a state of the discharge valve. 2. The switching system according to claim 1, wherein the control unit includes a delay unit that executes a switching operation of the discharge valve after a predetermined time has elapsed after recognizing the switching command of the discharge valve. . 3. The switching system according to claim 1, wherein the interlock mechanism uses a compressed gas and a mechanical valve operated by the compressed gas.