JPH03265180A - Gas processor and gas replacement of gas laser oscillator - Google Patents

Abstract

PURPOSE:To make it possible to replace gas in a short time by controlling in good order the process of transfer of the deteriorated gas in a discharge tube stopped from exciting to a gas container and return of the refreshed gas to the discharge tube. CONSTITUTION:When a command to replace the gas in a discharge apparatus 1A stopped from exciting is transmitted from a laser controller 26 to a gas processor controller 15, a valve 3A is opened and the gas in the apparatus 1A is transferred to a gas container 2 with a compressor 5A. A gas refreshing apparatus 7 is operated to remove halide, etc., and halogen gas and rare gas are injected from a gas addition apparatus 8 as required. When the gas in the container 2 is refreshed, a valve 4A is opened to return the refreshed gas to the apparatus 1A with a compressor 5B. The same operation is performed to refresh the gas in a discharge apparatus 1B. Thereby the gas can be replaced in a short time and constant laser output can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas processor for a gas laser oscillation device and a gas exchange method suitable for performing gas exchange of an excimer laser while keeping the output constant.

[Prior Art] Gas laser oscillation devices such as excimer lasers are widely used in optical CVD devices, laser lithography devices, and the like.

First, the gas laser oscillation device will be explained.

As an example of the gas laser oscillation device is shown in FIG. 5, the gas laser oscillation device is constructed by disposing a discharge device 1 within a laser resonator consisting of a total reflection mirror 22 and a semi-transmission mirror 23. Then, a part of the laser output is inputted to the output detector 25 via the reflection plate 24 provided on the laser output optical axis, and the output signal is transmitted to the power supply 27 of the discharge device 1 and the gas processor 9 via the control means 26. is controlled to keep the laser output constant.

FIG. 6(a) shows the laser output characteristics with respect to voltage of a conventional gas laser oscillation device. The laser oscillates above the voltage VSH, which is the oscillation threshold, and the maximum voltage Vm
The laser reaches maximum power at ax. Usually, devices with an oscillation threshold VSH of 15 kV and a maximum voltage Vmax of about 30 kV are often used.

FIG. 6(b) is an example showing the temporal change in laser output when a KrF excimer laser is used to oscillate with the voltage fixed at a certain value. After oscillation of about 2×106 shots, gas deterioration occurs and the laser output becomes about half of the value at the start. This time is about 2 hours and 50 minutes when operated with 2001-1z, which is too short for industrial use.

In order to compensate for such shortcomings of the conventional device, as shown in Fig. 7(a)
As shown in Figure 2, a method has been attempted in which the discharge voltage (2) is increased as the laser output is decreased. In this case, the maximum voltage V
When the maximum value is reached (time To), it is inevitable that the laser output decreases as shown in FIG. 7(b).

Additionally, as shown in Figure 8, a method has been attempted in which halogen gas, which causes severe deterioration, is injected when the laser output drops to a certain value (time Tt); Although the output recovers, it is theoretically impossible to keep the laser output constant, and there is also the problem that the gas pressure inside the device increases.

It is also conceivable to gradually replace the laser gas with new gas, but it is actually cumbersome to perform such control on an operating laser.

Next, a conventional gas processor used in such a gas laser device will be explained. Figure 9 shows JP-A-1-
An example of a discharge device and a conventional gas processor disclosed in Japanese Patent No. 268175 is shown. In this example, the gas processor 9 includes a gas purification device 10, a compressor 5, and a gas container 2. When this gas brosé nosa is operated during laser operation, the amount of laser medium increases by the amount of gas container 2, so the gas life is extended. However, its effectiveness is limited. Moreover, once the laser is stopped, it is possible to exchange the gas stored in the preliminary gas container with the gas in the discharge device in a short time. However, it has the disadvantage that laser output cannot be obtained while it is stopped. Thus, this example does not provide an essential solution to keeping the laser output constant.

[Problems to be Solved by the Invention] The present invention has been made in order to solve the above-mentioned problems, and provides a gas blower and a gas source suitable for a laser oscillation device that maintains a constant laser output for a long time. The purpose is to provide an exchange method.

[Means for Solving the Problems] The present invention provides: (1) A laser device in which a plurality of discharge devices are arranged in parallel, and one of the discharge devices is activated by one power supply device to emit laser output. A gas processor applied to any of the laser devices in which a plurality of discharge devices are arranged in series on a laser output optical axis, and one of the discharge devices is activated by one power supply device to irradiate laser output. and a gas exchange method.

The gas processor of the present invention includes a first compressor for extracting degraded gas from a stopped discharge device;
A gas container that stores the extracted degraded gas, a gas regeneration device that regenerates the degraded gas in the gas container, and a gas addition device;
It is characterized by comprising a second compressor that returns the regenerated gas to the stopped discharge device, and a gas processor controller for controlling each of the devices, and there is no connection between these devices or between these devices. It consists of piping and valves connecting to the discharge device, and a control network for the gas processor controller. Further, a halogen gas sensor and a pressure gauge may be provided as necessary.

Furthermore, the present invention provides a method for exchanging gas in these devices, including (a) a step of transferring gas in a stopped discharge device to a gas container, (b) a step of regenerating this gas, and (c) a step of discharging the regenerated gas in the container. Provided is a gas exchange method for a gas laser oscillation device, characterized in that the step of transferring the discharge device into the device is repeated in sequence for each discharge device.

[Function] According to the present invention, in a laser device in which two or more discharge devices are operated alternately, deteriorated gas in the discharge device in a stopped state is transferred to a gas container by a compressor, and the gas is regenerated by discharge using a gas regeneration device. The generated halides and, if necessary, halogen gas and particles are removed, and then halogen gas is added to form a laser gas with a specified composition, and the gas is returned to the discharge device using a compressor. The laser output loss can be kept to a minimum, and the normal laser output before gas deterioration can be restored when the laser goes from a stopped state to an operating state. Further, these operations can be performed in an orderly manner and in a short time by the gas processor controller.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of a gas processor 9 according to the present invention. In FIG. 1, the same members as in the conventional example are designated by the same reference numerals, and the explanation thereof will be omitted.

As shown in FIG. 1, a gas processor 9 according to the present invention includes a gas container 2. Compressor 5A, 5B, valve 3A, 3B
, -4A, 4B, gas regeneration device 7, gas addition device 8.
It is composed of a gas processor control device 15. The primary purpose of the gas regeneration device 7 is to remove halides, and in some cases halogen gas, but an impurity removal device such as an electrostatic filter or mesh or an oil trap may be incorporated as necessary.

Although FIG. 1 shows a configuration in which there are two discharge devices IA and IB, there may be three or more discharge devices. In that case, the number of vacuum pumps 6, compressors 5, and valves 3, 4 increases in accordance with the number of discharge devices.

An example of a laser device incorporating this gas processor 9 is shown in FIGS. 2 and 3. Examples will be described based on these figures.

Example 1 First, the operation of the laser device will be explained.

In Figure 2, each laser oscillator (discharge device) l
A part of the laser output from A and IB is reflected by the reflection plates 24A and 24A.
4B and irradiates the output monitors 25A and 25B, where it is converted into an electric signal, and the electric signal controls the power supply device 27 and the gas processor 9 via the control means 26. A high voltage switch 2 is connected to the output end of the power supply device 27.
9A and 29B are provided, and alternately apply and stop the application of voltage to the two discharge devices IA and IB via voltage circuits 2OA and 20B, respectively. Note that the laser output from the discharge device IA can directly irradiate the object to be irradiated, but the laser output from the discharge device IB
After the optical axis of the laser output is adjusted by the reflecting mirrors 21A and 21B, it is irradiated onto the object to be illuminated.

Here, to further explain the function of the control means 26, the electric signal of the output monitor 25A (or 25B) is compared with a target value of the laser output given in advance,
The applied voltage of the power supply device 27 is controlled so that the deviation between the two becomes O, and further, just before the applied voltage reaches around the maximum voltage, the voltage circuit 20A (or or 20B) with two high voltage switches A (or 29B), and at the same time open high voltage switch 2
Close 9B (or 29A) and install a new discharge device IB
(or IA), a voltage is applied to the output monitor 25B (or IA), and the output monitor 25B (
or 25 A), and the laser oscillation is sustained.

The control means 26 is also used to drive the gas processor 9 of the present invention and replace the gas in the discharge device IA whose discharge has been interrupted with new gas.

Next, an example of controlling the gas laser oscillation device configured as described above will be explained using FIG. 3. This figure is Kr
Discharge device IA, l when performing F excimer laser oscillation
It shows the time course of the voltage applied to B and the laser output.

In advance, fill both discharge devices 1A and IB with fresh gas, and first repeat the discharge device IA at a frequency of 20.
0. Operated at Hz. In the first period, as the gas in the discharge device IA deteriorates, the voltage (VA) applied to the discharge device IA increases.
After about 2 hours (approximately 1.5 x 1O6 shot), high voltage switch 29A was opened to stop the discharge (first
cycle ends). At the same time, the high voltage switch 29B was closed and the discharge device IB was operated at a repetition frequency of 200Hz (second
cycle start). In this second period, since the discharge device IB was filled with fresh gas, the same applied voltage (v8) and laser output characteristics as in the first period were obtained. On the other hand, in this second cycle, the gas processor 9 of the present invention was driven to replace the degraded gas in the discharge device IA, which had stopped oscillation, with fresh gas, and was placed on standby for the next cycle.

In this control example, by alternately switching the discharge devices IA and IB and exchanging the gas, control was performed up to the 6th cycle, and it was possible to suppress the fluctuation in output to within 1% during approximately 12 hours of operation. .

Among these series of operations, the operation of the gas processor 9 of the present invention will be explained. From the laser control means 26, the second
When the cycle starts, a command is issued to the gas processor controller 15 shown in FIG. 1 to replace the deteriorated gas in the discharge device IA, which has stopped oscillation, with fresh gas. From this point on, a series of operations of the gas processor 9 starts.

First, the valve 3A is opened and the gas in the discharge device IA is transferred to the gas container 2 by the compressor 5A. At this time, the vacuum pump 6A may be used if necessary.

Valve 3A is closed at the time of transfer.

Next, the operation of the gas regeneration device 7 is started in order to regenerate the gas in the gas container 2. The gas regeneration device 7 is a device for removing halides and, depending on the case, halogen gas, O2, oil, and the like. Also, if necessary,
Devices for particle removal can also be added. The device for removing particles is, for example, a transmission filter or an electrostatic filter.

At this time, the concentration of halogen gas is detected, and halogen gas and rare gas are injected from the gas addition device 8 as necessary. When the gas in the gas container 2 is regenerated in this way,
Open valve 4A and supply gas to compressor 5B as necessary.
The regenerated gas is returned from the operated gas container 2 to the discharge device IA. After returning the gas, close the valve 4A. When returning the gas, the pump 6B may be used if necessary.

In this way, the gas processor controller 15
In order to manage the opening and closing of A, 5B, gas regeneration device 7, gas addition device 8, and each valve in an orderly manner, the time required for the series of operations in step 6 is approximately 15 minutes, and the second cycle time is 2 hours and 30 minutes. is sufficiently short compared to . In the third cycle, the gas processor operates in the same manner as above to regenerate the gas in the discharge device IB.

Further, as the role of the gas processor 9, halogen gas can also be supplied to the laser discharge device in operation.

In this case, gas container 12 and valves 13A and 13B are used. Pump 11 is used to evacuate the gas container. Taking the second cycle as an example, the gas in the discharge device 1A (or IB) during discharge is determined in response to the difference between the electrical signal of the output monitor 25A (or 25B) and the target value of the laser output to the gas processor 9. It may be used to control the system and adjust the gas supply so that the laser output is constant.

Vacuum pumps 6A, 6B, and 14.11 in FIG. 1 are used to evacuate the discharge device and gas container.

Although the above embodiment describes the case where two discharge devices are arranged in parallel, the present invention is not limited to this, and two discharge devices are arranged in parallel.
Needless to say, any number of devices may be used as long as the number of devices is greater than one.

Example 2 Another example is shown in FIG. First, the operation of the laser will be explained. In the embodiment shown in FIG.
Two discharge devices 1A and 1B are arranged in series in a resonator consisting of a mirror 2 and a semi-transparent mirror 23, and this configuration prevents the optical axis of the laser beam from being deviated. The reflecting mirrors 2LA and 21B shown in FIG. 2 indicated by 1 are no longer necessary.

Furthermore, when applied to a laser lithography apparatus, it is necessary to narrow the wavelength band, and in that case, a band narrowing element such as an etalon plate is often installed inside the laser resonator. Since it becomes possible to use the six band narrowing elements in common, the cost can be lowered compared to the first embodiment.

The operation of the gas processor 9 is similar to that in the first embodiment.

In addition, although the above embodiment shows a case where two discharge devices are arranged in parallel, the present invention is not limited to this, and it goes without saying that any number of discharge devices may be used as long as there are two or more discharge devices.

[Effects of the Invention] According to the present invention, a plurality of discharge devices are used, and deteriorated gas is transferred to a fixed gas container for the stopped discharge devices, and halides contained in the gas are removed as necessary. The laser output is kept constant by removing halogen gas, 02, and impurities, then adding halogen gas and rare gas as the case requires, regenerating the gas, and then transferring it to the discharge device again. became possible. These series of operations can be performed in an orderly manner by the gas processor controller.

Further, since the buffer gas such as He or Ne, which occupies most of the volume, is not consumed while only consuming some halogen gas, running costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIGS. 2 and 4 are block diagrams of a laser device operated using the present invention,
Fig. 3 is a chart showing an example of laser output control, Fig. 5 is a block diagram showing an example of a conventional laser device, Figs. 6, 7, and 8 are examples of conventional laser output, and Fig. 9 is a chart showing an example of laser output control. FIG. 1 is a block diagram showing an example of a conventional laser device. IA, IB...Discharge device 2...Gas containers 3A, 3B...Valves 4A, 4B...Valves 5A, 5B...Compressors 6A, 6B...Vacuum pump 7...Gas regeneration device 8...Gas addition device 9...Gas processor 11...-Vacuum pump 12...Gas container 15...Gas processor controller

Claims (1)

[Scope of Claims] 1. A gas processor for a gas laser oscillation device that operates a plurality of discharge devices by switching them alternately or sequentially, comprising: a first compressor for extracting degraded gas from a discharge device that has stopped oscillation; and the compressor. a gas container that stores the degraded gas extracted by the gas container, a gas regeneration device that regenerates the degraded gas in the gas container, a gas addition device, and a second compressor that returns the recycled gas to the stopped discharge device. , and a gas processor controller for controlling each of the devices. 2. A gas exchange method for a gas laser oscillation device in which a plurality of discharge devices are operated by switching them alternately or sequentially, which includes a step of transferring gas in a stopped discharge device to a container, a step of regenerating the gas in the container, and a step of regenerating the gas in the container. 1. A gas exchanging method for a gas laser oscillation device, characterized in that the step of transferring gas in a container into a discharge device is repeatedly performed for each discharge device in sequence.