JPH0997951A - Excimer laser apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excimer laser apparatus in which the injection interval of halogen gas is expanded, in which the cause of the instability of a laser oscillation is reduced and in which the contamination of an optical system can be discriminated. SOLUTION: In an excimer laser apparatus, the laser output of a laser oscillation container 2 is detected 4, the charging voltage of a high-voltage power supply 10 is controlled 14 so as to obtain a constant laser output, and halogen gas 7 is injected into the laser oscillation container when the charging voltage reaches a predetermined set voltage value by a comparison circuit 17. In the excimer laser apparatus, a second set voltage value which is smaller than the predetermined set voltage value is set, and the injection of the halogen gas is finished when the inversion transition of the charging voltage does no exceed the second set voltage value by comparison circuits 20, 21 in the injection of the halogen gas. In addition, the excimer laser apparatus is provided with the injection control part, of the halogen gas, which finishes the injection of the halogen gas when the inversion transition of the charging voltage exceeds the second set voltage value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excimer laser device, and more particularly to halogen gas supply during long-term operation.

[0002]

2. Description of the Related Art In an excimer laser device, a mixed gas of a rare gas (Ar, Kr, Xe, etc.) and a halogen gas (F2, HCl, etc.) is enclosed in a laser oscillation container, and discharge is performed in the mixed gas. This is a device that excites a mixed gas to oscillate a pulse laser (excimer laser) in the ultraviolet region. The oscillation wavelength of the excimer laser light emitted from the excimer laser device is a combination of a component used as a rare gas and a component used as a halogen gas. It will be different depending on the combination.

By the way, since halogen gas has extremely high reactivity, it reacts with an electrode metal for discharge in the laser oscillation container during operation of the excimer laser device to generate a halogen compound as an impurity. The halogen compound thus generated absorbs the oscillated laser light, adheres to the optical system in the laser oscillation container to stain the optical system, and causes a decrease in halogen itself. As a result, the output of the excimer laser light output from the laser oscillation container is gradually reduced, and the life of the shut-off laser is shortened.

Therefore, as a measure for preventing the occurrence of such an inconvenience, conventionally, the excimer laser device itself is equipped with a gas purifying means and a halogen gas supplying means in advance. . The gas purification means is, for example, an impure gas trap device such as a cooling trap,
It consists of a dust collector such as a filter, and the mixed gas in the laser oscillation container is circulated to this impure gas trap device or dust collector to reduce the concentration of impurities in the mixed gas in the laser oscillation container, halogen compounds, etc. In addition to reducing the absorption of laser light by the impurities, the contamination of the optical system is reduced.

Further, the halogen gas supply means is a halogen gas cylinder with an opening / closing valve, and when the halogen gas concentration in the laser oscillating container is lowered, the opening / closing valve is operated to supply a fixed amount of halogen gas in the laser oscillating container. The halogen gas concentration in the laser oscillation container decreases due to the generation of the halogen compound, and accordingly, the halogen gas is replenished to the laser oscillation container at an appropriate time to prevent the occurrence of inconvenience caused by the decrease in the halogen gas concentration. It is a thing.

In this case, the decrease in the halogen gas concentration in the laser oscillation container is detected by detecting the output of the laser light output from the laser oscillation container, and when the output of the laser light is reduced, a fixed amount is detected. This is supported by so-called halogen gas injection, in which a halogen gas is injected into the laser oscillation container.

Further, in a long-time continuous operation with a constant laser output, the charging voltage of the high voltage power source applied to the discharge electrode in the laser oscillation container is changed according to the fluctuation of the laser output to control the constant laser output. In this case, the charging voltage is raised because the charging voltage decreases the output due to the decrease in halogen gas. When the rise exceeds a predetermined value, a certain amount of halogen gas is injected into the laser oscillation container, the charging voltage is lowered again, and the operation is continued.

[0008]

However, as described above, in the method of injecting a certain amount of halogen gas into the laser oscillation container when the charging voltage value exceeds a predetermined value,
Since the optimum amount of halogen gas cannot be injected, the interval of halogen gas injection becomes short. Therefore, there are many occasions when the halogen concentration in the laser oscillation container becomes excessively non-uniform, which makes laser oscillation unstable, and downtime occurs each time the operation is stopped and halogen gas is supplied. Becomes less efficient. In addition, the laser container is filled with laser gas containing halogen gas at several atmospheres,
In order to inject the halogen gas by frequently opening and closing the valve in such a state, safety measures become complicated.

Further, there is another factor in the reduction of the laser output (mostly considered to be contamination of the optical system), but the above-mentioned method does not take this into consideration. That is, when the laser output is reduced due to other factors, the laser light is similarly supplied, and as a result, the output may not be improved.

The present invention has been made in view of the above situation, and can supply an optimum amount of halogen gas, extend the injection interval of halogen gas to reduce the factor of destabilizing laser oscillation, and at the same time, to provide an optical system. It is an object of the present invention to provide an excimer laser device capable of discriminating the dirt of the.

[0011]

The above object of the present invention is to apply a laser oscillation container having a discharge electrode for forming excimer laser light by performing discharge in a mixed gas containing a halogen gas, and to the discharge electrode. A high-voltage power supply, a laser light detection circuit for detecting the output of the laser oscillation container, and a halogen gas supply means for supplying a halogen gas to the laser oscillation container, according to the detection output of the laser light detection circuit While controlling the charging voltage of the high voltage power supply,
In the excimer laser device which operates the halogen gas supply means and injects halogen gas into the laser oscillation container when the charging voltage reaches a predetermined first set voltage value, Is set in advance, and when the inversion transition of the charging voltage does not exceed the second setting voltage value when the halogen gas is injected, the injection of the halogen gas is terminated and the charging voltage is changed. A halogen gas injection control unit that terminates the injection of the halogen gas when the charging voltage exceeds the second set voltage value when the inversion transition of the above exceeds the second set voltage value. This is achieved by using a characteristic excimer laser device.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An excimer laser device which detects an output laser of a laser oscillation container and controls a charging voltage of a high-voltage power source to obtain a constant laser output has a relationship between a charging voltage and a halogen gas concentration. However, as shown by the curve A in FIG. 2, it has a substantially parabolic characteristic in which the charging voltage becomes minimum when the halogen gas concentration is the optimum value. The present invention utilizes this characteristic, and sets the charging voltage when the halogen gas concentration is lower than the optimum value and the halogen gas needs to be injected, as the first voltage setting value Va. Is set to a (a constant of 0, 9 to 0, 99) and a second voltage setting value aVa is set.

The charging voltage is the first voltage set value Va.
The charging voltage is monitored from the time when the injection of the halogen gas is exceeded, and the reversal transition of the charging voltage, that is, the reversal time point from the decrease to the increase of the charge voltage is the second voltage setting value aVa.
It is determined whether or not it exceeds. When the reversal time does not exceed the second voltage setting value aVa (dotted line curve B in FIG. 2),
It is assumed that the laser oscillation container is deteriorated due to contamination, the injection of halogen gas is completed, and the operation of the excimer laser device is stopped.
When the reversal time exceeds the second voltage set value aVa (curve A in FIG. 2), the halogen gas concentration is decreased until the charging voltage reaches the second voltage set value aVa (point Y in FIG. 2). The injection of halogen gas is continued and the excimer laser device continues to operate.

[0014]

1 is a block diagram of an excimer laser device according to an embodiment of the present invention. The excimer laser device 1 according to this embodiment is shown in FIG.
Is a laser oscillation container 2 that performs laser oscillation by discharging and exciting in a mixed gas of a rare gas and a halogen gas.
A high voltage power supply 10 for applying a high voltage to the discharge electrode 9 in the laser oscillation container 2, a split mirror 12 arranged in the optical path of the excimer laser light 3 output from the laser oscillation container 2, and the split. A laser light output detection circuit 4 that receives a part of the laser light 3 through the mirror 12 and detects the output of the laser oscillation container 2, and a gas purification unit that removes impurities in the mixed gas in the laser oscillation container 2. 6 and
The halogen gas supply means 7 for injecting a halogen gas into the laser oscillation container 2 and the detection signal from the laser light output detection circuit 4 are input to operate the high-voltage power supply 10, the gas purification means 6, the halogen gas supply means 7, and the like. Control unit 1 for controlling
1 is provided.

The gas purification means 6 is, for example, an impure gas trap device such as a cooling trap, a dust collector such as a filter, and a gas circulation device for circulating the mixed gas in the laser oscillation container 2 to the impure gas trap device and the dust collector. Etc., the mixed gas in the laser oscillation container 2 is circulated to an impure gas trap device or a dust collector at appropriate times to reduce the concentration of impurities in the mixed gas in the laser oscillation container 2 and to emit laser light by impurities such as halogen compounds. Of the optical system, and at the same time, reduces the contamination of the optical system. The halogen gas supply means 7 is a halogen gas cylinder with an opening / closing valve, and supplies the halogen gas to the laser oscillation container 2 by opening / closing the opening / closing valve.

FIG. 2 is a diagram showing the relationship between the halogen gas concentration and the charging voltage under a constant laser output. As shown by the curve A, the relationship between the halogen gas concentration and the charging voltage is that the halogen gas concentration is 0. The charging voltage becomes the minimum when the optimum value is in the range of 1 to 0.2%, and the charging voltage becomes higher as the halogen gas concentration becomes lower or higher than the optimum value. Become a state.

In this embodiment, the control section 11 is provided with a charging voltage setting circuit 14 for setting and controlling the charging voltage of the high voltage power source 10, and the high voltage power source 10 is charged according to the decrease in the detection value of the laser light detecting circuit 4. The voltage is set high and the laser oscillation container 2
The laser light 3 output from the device is kept constant.

Further, the control unit 11 is provided with a halogen gas injection control unit 15 for operating the open / close valve of the halogen gas supply means 7 to inject the halogen gas into the laser oscillation container 2.
When the halogen gas amount (concentration) in the laser oscillation container 2 decreases, the halogen gas is injected into the laser oscillation container 2 to maintain the halogen gas amount (concentration) in the laser oscillation container 2 at an optimum value state. ing.

Therefore, the halogen gas injection controller 15
Is the charging voltage value Vx set by the charging voltage setting circuit 14 and a predetermined first value as shown in the block circuit of FIG.
Set voltage value Va (a halogen gas injection start voltage value, FIG.
Va) of the first comparison circuit 17 for comparing the charging voltage value Vx set by the charging voltage setting circuit 14 with the first setting voltage value Va, and the charging voltage value Vx is the first setting voltage. When the value Va is exceeded, the opening / closing valve (halogen gas valve) of the halogen gas supply means 7 is opened to start injecting the halogen gas into the laser oscillation container 2 at a constant flow rate of 1 to 100 torr / min.

Further, the halogen gas injection control unit 15 detects the charging voltage value Vx at regular intervals from the time when the charging voltage value Vx exceeds the first set voltage value Va, and the charging voltage monitor circuit 18 and the charging voltage monitor. The memory circuit 19 that stores the charging voltage value Vx detected by the circuit 18, the charging voltage value Vn at the time of detection by the charging voltage monitor circuit 18, and the memory circuit 1
The charging voltage value Vn and the first set voltage value Va detected at the second comparison circuit 20 and the charging voltage monitor circuit 18 for comparing the immediately preceding charging voltage value Vn-1 stored in 9 with a ( A constant from 0, 9 to 0, 99, 0, 95 in this example.
2) the second set voltage value (aV in FIG. 2)
and a third comparison circuit 21 for comparing with a).

The halogen gas injection controller 15 constructed as described above operates as shown in FIG. That is, when the halogen gas injection into the laser oscillation container 2 is started (step 101), the charging voltage value Vx set by the charging voltage setting circuit 14 is detected by the charging voltage monitor circuit 18 at regular intervals, and the detected voltage at that time is detected. The value Vn is stored in the memory circuit 19 (step 103). Then, the previously detected detection voltage value Vn-1 is read from the memory circuit 19 (step 1
04), the detected voltage value Vn detected this time and the detected voltage value Vn-1 of the previous time are compared by the second comparison circuit 20 (step 105).

When the detected voltage value Vn detected this time is smaller than the detected voltage value Vn-1 detected last time in the comparison of this step 105, the halogen gas injection is continued as it is, and the process returns to step 103 to detect the detection detected this time. Voltage value V
When n is larger than the previously detected detection voltage value Vn−1, the halogen gas valve of the halogen gas supply means 7 is closed to stop the injection of the halogen gas into the laser oscillation container 2 (step 106), and the third The comparison circuit 21 compares the detected voltage value Vn detected this time with the second set voltage value aVa (step 107).

When the detected voltage value Vn detected this time is smaller than the second set voltage value aVa in the comparison of step 107, the halogen gas valve is opened to feed the laser oscillation container 2 at a constant flow rate of 1 to 100 torr / min. Of the halogen gas is started (step 108), the charging voltage value Vx set by the charging voltage setting circuit 14 is detected by the charging voltage monitor circuit 18 at regular intervals (step 109), and the detected voltage value Vn at that time and the The second set voltage value aVa
The comparison circuit is compared (step 110).

When the detected voltage value Vn detected this time is smaller than the second set voltage value aVa in the comparison of step 110, the halogen gas injection is continued as it is, and the process returns to step 109 to detect the detected voltage value this time. When Vn is larger than the second set voltage value aVa, the halogen gas valve is closed to terminate the halogen gas injection into the laser oscillation container 2 (step 111). In this case, the operation of the laser device is continued. This step 109 and 110
By repeating the above procedure, a large amount of halogen gas is injected into the laser oscillation container 2 as indicated by a point Y in FIG. As a result, the halogen gas injection interval is extended to prevent destabilization of laser oscillation.

In the comparison of step 107, when the detected voltage value Vn detected this time is larger than the second set voltage value aVa, the halogen gas valve is closed to complete the injection of the halogen gas into the laser oscillation container 2 ( Step 11
2). In this case, the state of the curve B shown by the dotted line in FIG. 2, that is, the increase of the charging voltage value Vx set by the charging voltage setting circuit 14 is not based on the decrease of the halogen gas concentration, but the window plate of the laser oscillation container 2 becomes dirty. caused by. Therefore,
In this case, the operation of the laser device is stopped and a warning for cleaning the laser oscillation container 2 is given.

In the embodiment of the halogen gas injection controller 15 shown in FIGS. 3 and 4, the halogen gas is injected into the laser oscillation container 2 at a constant flow rate, but it is 1 to 10 torr.
The operation of the embodiment of the halogen gas injection control unit in that case, which can also be configured to inject a fixed amount, will be described with reference to FIG. The block circuit of the halogen gas injection control unit is the same as that shown in FIG.

In the embodiment shown in FIG. 5, the first comparison circuit 1
In step 7, the charging voltage value Vx set by the charging voltage setting circuit 14 is compared with the first setting voltage value Va, and the charging voltage value Vx becomes the first value.
When the set voltage value Va is exceeded, the opening / closing valve (halogen gas valve) of the halogen gas supply means 7 is opened to inject a fixed amount of 1 to 10 torr of the halogen gas into the laser oscillation container 2 (steps 201, 202) and constant. After injecting the amount, the halogen gas valve is closed (step 203).

Then, the charging voltage value Vx set by the charging voltage setting circuit 14 is detected by the charging voltage monitor circuit 18, and the detected voltage value Vn at that time is stored in the memory circuit 19 (step 204). The detected voltage value Vn-1 detected is read (step 205), and the detected voltage value Vn detected this time and the detected voltage value Vn-1 of the previous time are secondly read.
The comparison circuit 20 makes a comparison (step 206).

In the comparison in step 206, when the detected voltage value Vn detected this time is smaller than the detected voltage value Vn-1 detected last time, the process returns to step 202 and a fixed amount of halogen gas is injected. When the detected voltage value Vn detected this time is larger than the detected voltage value Vn−1 detected last time, the detected voltage value Vn detected this time by the third comparison circuit 21 and the second
The set voltage value aVa of the above is compared (step 207).

When the detected voltage value Vn detected this time is smaller than the second set voltage value aVa in this comparison of step 207, the halogen gas valve is opened to inject a fixed amount of halogen gas into the laser oscillation container 2. (Step 20
8) After the injection of a fixed amount, the halogen gas valve is closed (step 209). Then, the charging voltage value Vx set by the charging voltage setting circuit 14 is detected by the charging voltage monitor circuit 18 (step 210), and the detected voltage value Vn at that time and the second set voltage value aVa are detected by the third comparison circuit. The comparison is made (step 211).

If the detected voltage value Vn detected this time is smaller than the second set voltage value aVa in this comparison of step 211, the process returns to step 208 to inject a fixed amount of halogen gas into the laser oscillation container 2, and this time. When the detected detection voltage value Vn is larger than the second set voltage value aVa, the halogen gas injection into the laser oscillation container 2 is terminated (step 212). In this case, the operation of the laser device is continued. Repeating these steps 208 and 211 results in a large amount of halogen gas to be injected into the laser oscillation container 2 as indicated by point Y in FIG. As a result, the halogen gas injection interval is extended to prevent destabilization of laser oscillation.

When the detected voltage value Vn detected this time is larger than the second set voltage value aVa in the comparison of step 207, the halogen gas injection into the laser oscillation container 2 is terminated (step 213). In this case, the state of the curve B shown by the dotted line in FIG. 2, that is, the increase of the charging voltage value Vx set by the charging voltage setting circuit 14 is not based on the decrease of the halogen gas concentration, but the window plate of the laser oscillation container 2 becomes dirty. caused by. Therefore, in this case, the operation of the laser device is stopped, and a warning for cleaning the laser oscillation container 2 is issued.

As described in detail above, in the halogen gas injection control according to the present invention, the charging voltage of the high voltage power supply is monitored while the halogen gas is injected into the laser oscillation container 2, and the charging voltage of the high voltage power supply is monitored. When the charging voltage reverses from the falling state to the rising state at a voltage value that is smaller than the first voltage setting value that is a predetermined halogen gas injection start voltage and that is smaller than the second voltage setting value that is predetermined. Finish the gas injection.

When the charging voltage of the high-voltage power supply changes from the falling state to the rising state at a voltage value smaller than the second voltage setting value, the charging voltage of the high-voltage power source is set to the second voltage setting value. When the value is exceeded, the halogen gas supply is stopped. In this way, it is determined whether the output of the excimer laser device is reduced due to the reduction of the halogen gas concentration or the contamination of the laser oscillation container, and a large amount of halogen gas (halogen gas concentration) is injected at one injection time. are doing.

[0035]

As described above, according to the present invention, it is possible to easily determine the cleaning time or the replacement time of the laser oscillation container, and the halogen gas injection interval is extended so that the laser oscillation during the halogen gas injection can be prevented. The factor of destabilization can be reduced, and long-time continuous operation with a constant laser output becomes possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an excimer laser device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a correlation between a halogen gas concentration and a charging voltage under a constant laser output.

FIG. 3 is a block circuit diagram of a halogen gas injection control unit of the excimer laser device of FIG.

FIG. 4 is a flowchart showing the operation of the halogen gas injection control unit according to the embodiment of the present invention.

FIG. 5 is a flowchart showing the operation of a halogen gas injection control unit according to another embodiment of the present invention.

[Explanation of symbols]

 1 Excimer Laser Device 2 Laser Oscillator 3 Laser Light 4 Laser Light Detection Circuit 6 Gas Purification Means 7 Halogen Gas Supply Means 9 Discharge Electrode 10 High Voltage Power Supply 11 Control Unit 12 Split Mirror 14 Charging Voltage Control Unit 15 Halogen Gas Injection Control Unit 17 First comparison circuit 18 Charge voltage monitor circuit 19 Memory circuit 20 Second comparison circuit 21 Third comparison circuit

Claims (1)

[Claims] 1. A laser oscillation container having a discharge electrode for forming an excimer laser beam by performing discharge in a mixed gas containing a halogen gas, a high voltage power supply applied to the discharge electrode, and an output of the laser oscillation container. Laser light detection circuit for detecting, and a halogen gas supply means for supplying a halogen gas to the laser oscillation container, while controlling the charging voltage of the high-voltage power supply according to the detection output of the laser light detection circuit In the excimer laser device that operates the halogen gas supply means to inject halogen gas into the laser oscillation container when the charging voltage reaches a predetermined first set voltage value, the first set voltage value A second set voltage value smaller than the above is set in advance, and when the inversion transition of the charging voltage does not exceed the second set voltage value when the halogen gas is injected, Ending the injection of the halogen gas,
And a halogen gas injection control unit that terminates the injection of the halogen gas when the charging voltage inversion transition exceeds the second set voltage value and the charge voltage exceeds the second set voltage value. An excimer laser device characterized in that