JPH0697541A - Gas purifying apparatus for excimer laser and gas purifying method - Google Patents

Abstract

PURPOSE:To use rare gas like Kr without waste which gas is previously adsorbed by adsorbent, prior to laser operation. CONSTITUTION:Considering that, before a laser 1 is practically operated, so- called shakedown is performed wherein the laser 1 is oscillated with operating gas composition called passivation, or the total exchange of gas is performed after some operation time. The title gas purifying apparatus 4 for an excimer laser which oscillates while circulating gas medium for laser oscillation which contains rare gas through a laser tube 2 and an adsorbing tower 9 containing adsorbent. Prior to laser oscillation, rare gas can be previously adsorbed by adsorbent contained in the adsorbing tower. As the rare gas to be previously adsorbed, the rare gas in the gas medium for laser oscillation which has been used in the preceeding laser oscillation is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excimer laser gas purifying apparatus and a gas purifying method, and particularly to purifying a multi-component gas which is circulated and used while purifying a gas medium such as a laser gas medium. The present invention relates to a gas purification apparatus and a gas purification method for an excimer laser that are made possible.

[0002]

2. Description of the Related Art The technology of a conventional gas purifying apparatus for an excimer laser will be described below by taking a KrF excimer laser as an example.

The KrF excimer laser has a laser tube made of glass or the like and has a gas medium for laser of about 98% neon gas (Ne) (buffer gas), about 2%.
% Krypton gas (Kr) and about 0.1% fluorine gas (F2) are contained, mirrors are arranged at both ends, and a laser gas medium is caused to discharge and emit light to cause resonance. To operate.

Since the above-mentioned fluorine gas is highly reactive and the fluorine gas excited by the discharge is particularly reactive, the fluorine gas reacts with the impurities and other constituent materials in the laser gas medium by the discharge. As a result, there is a problem that impurities such as CF4, HF and SiF4 are generated in the laser tube, and the laser output of the KrF excimer laser decreases as the number of discharges increases.

As a gas purification method for such a KrF excimer laser, there is a cold trap method that utilizes the difference in the boiling point temperature of the gas. However, depending on the type of gas, it is difficult to use it if the boiling point temperatures are close to each other. There is.

A method using an adsorbent has also been proposed, and there are Japanese Patent Application No. 3-132913 and Japanese Patent Application No. 3-132914 by the applicant of the present invention. First, it is necessary to adsorb Kr on the adsorbent in advance.

That is, before being connected to the laser tube, Kr is adsorbed to the adsorbent so that it has the same equilibrium with the Kr composition (2%) of the gas medium for laser, and Ne of the buffer gas is operated at an operating pressure (4 It is necessary to adjust to atmospheric pressure).

However, in such an adsorption method before the operation, the Kr to be adsorbed on the adsorbent is used excessively or in vain, and some measures have been demanded.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and purifies the gas by removing the impurities of the multi-component gas medium in which impurities are generated, while maintaining a constant value for a long period of time. A gas purification apparatus and a gas purification method for an excimer laser, which can easily obtain a laser output and can use a rare gas such as Kr that is adsorbed in an adsorbent in advance before a laser operation without waste. The challenge is to provide.

[0010]

That is, according to the present invention, before the laser is operated, the laser is oscillated with an operating gas composition called passivation, that is, a so-called run-in operation is performed, or the gas is totally replaced by some operation. The first invention is an excimer laser that oscillates a laser while circulating a gas medium for a laser containing a rare gas between a laser tube and an adsorption tower containing an adsorbent. A gas purifying apparatus for use, wherein the adsorbent accommodated in the adsorption tower is capable of adsorbing the rare gas in advance prior to laser oscillation, and is used as the rare gas to be adsorbed in advance in the previous laser oscillation. A gas purifying apparatus for an excimer laser, characterized by using a rare gas in the laser gas medium.

A halogen removal tower capable of removing the halogen in the laser gas medium can be arranged in front of the adsorption tower.

The rare gas previously adsorbed by the adsorbent may be krypton (Kr).

The halogen removal tower may be a fluorine gas (F2) removal tower.

The adsorption equilibrium pressure of the rare gas previously adsorbed on the adsorbent and the operating pressure of the buffer gas can be filled with a compressor.

A second invention is a gas purification method of an excimer laser in which a laser gas medium containing a rare gas is oscillated while being circulated between a laser tube and an adsorption tower containing an adsorbent. , The adsorbent contained in the adsorption tower, the rare gas in the gas medium for laser is pre-adsorbed to the adsorbent by passing the gas medium for laser used in the previous laser oscillation,
Next, there is provided a gas purification method for an excimer laser, which comprises supplying a fresh laser gas medium to the laser tube to cause laser oscillation.

Next, the present invention will be described more specifically based on various data. FIG. 1 is a graph showing vapor pressure curves of laser gas and impurity gas.

In the KrF excimer laser, the necessary component gases of the laser gas medium are Ne, Kr and F2, and the main impurity gases are CF4, HF and SiF4.

Of these gases, as shown in FIG.
Kr and CF4 have vapor pressure curves that are very close to each other, and the vapor pressure curve of Kr sharply decreases near the liquid nitrogen temperature.

FIG. 2 shows Kr at a temperature of minus 81 ° C.
5 is a graph showing the adsorption amount of CF4 and CF4 on activated carbon (adsorption equilibrium curve).

FIG. 3 is a graph showing an adsorption equilibrium curve of CF4 in the presence of Kr, showing the concentration of Kr which has been saturated and adsorbed at a predetermined concentration under a pressure of the buffer gas Ne of 4 atm. Instead, the amount of CF4 adsorbed is shown.

As shown in the figure, the amount of CF4 adsorbed shows a characteristic that depends on the concentration of Kr. In a KrF excimer laser, the concentration of Kr is usually 2%, so the concentration of CF4 is 100 ppm (0.304 Torr). Then, 0.
8 Ncc / g of CF4 is adsorbed.

FIG. 4 is a graph showing the adsorption of xenon (Xe) and krypton (Kr) on activated carbon (RD Ackley, RE Adams,
W. E. Browning: TID-7593, 1
99-216 (1961)).

FIG. 5 shows K by Columbia CLA activated carbon.
3 is a graph showing adsorption of r (JN Burdic)
k: ORO-118 (1951)).

Based on the above data, in the gas purification apparatus for an excimer laser according to the present invention, a refrigerator (not shown) is used as the exhaust gas at the time of the leveling operation of the laser or the total replacement of the gas in the laser tube. A rare gas such as Kr is saturated and adsorbed on the adsorbent by passing through the adsorbent that has been cooled in advance.

If halogens and halides such as F2 and HF may be harmful to the adsorbent, F
2 The exhaust gas may be passed through the removal tower to remove them and then introduced into the adsorption tower.

The numerical value of each parameter is, for example, KrF.
In the case of an excimer laser, the operating pressure is 4 atm, the buffer gas is Ne, Kr is 1 to 2%, F2 is 0.1%, and the adsorbent temperature is 100 to 200K.

[0027]

In the gas purifying apparatus for excimer laser according to the present invention, the exhaust gas at the time of break-in operation or total replacement is introduced into the adsorption tower in the form of reuse and Kr is adsorbed in advance through the adsorbent. There is.

Therefore, the costly Kr and Ne gases can be saved, and if the pressure in the adsorption tower is raised to the operating pressure of the laser by the compressor, the adjustment of the Kr concentration and the filling of Ne become very easy.

[0029]

EXAMPLE Next, an excimer laser equipped with a gas purifying apparatus according to an example of the present invention will be described.

The excimer laser 1 has a laser main body 2 including a laser tube, a circulation pump 3, a gas purifying device 4 including an adsorption tower, an inlet side valve 5, and an outlet side valve 6, and each component. The members are connected by pipes to form the circulation passage 7.

An exhaust gas supply passage 8 is provided in parallel with the circulation passage 7, and an F2 removal tower 9, a compressor 10 connected to the gas purification device 4, and an opening / closing valve 11 are provided therein.

The circulation pump 3 allows the laser gas medium from the laser body 2 to pass through the circulation passage 7 to the gas purification device 4 and circulates to the laser body 2.

The gas purifier 4 contains an adsorbent and is capable of adsorbing fluorides (impurities) such as CF4, HF and SiF4 and Kr, and is cooled from a temperature of 77K to room temperature by a refrigerator (not shown). The temperature can be adjusted up to.

The F2 removal tower 9 contains a halogen adsorbent such as activated carbon capable of removing halogen, and operates at room temperature.

The exhaust gas of the laser body 2 supplied to the gas purifying device 4 through the exhaust gas supply passage 8 comes into contact with the adsorbent inside and is then exhausted to the outside of the gas purifying device 4. ing.

In the excimer laser 1 having such a configuration, the gas purifying device 4 is set to K before normal laser oscillation.
Saturate adsorption of r.

In this adsorption, the inlet side valve 5 and the outlet side valve 6 are closed, and the opening / closing valve 11 is opened so that the laser body 2 is run-in or the exhaust gas of the previous laser oscillation (inside the laser body 2) Gas) F2
The gas is supplied to the gas purification device 4 via the removal tower 9 and the exhaust gas supply passage 8.

F2 in the exhaust gas is removed in the F2 removal tower 9, and only the inert gas such as Kr and the impurities (fluorides) in the gas medium for laser are supplied to the gas purifying device 4, and Kr is increased. It is saturatedly adsorbed by the adsorbent in the gas purification device 4.

Impurities such as CF4 and HF are also adsorbed at the same time, and gases such as Ne are not adsorbed and are exhausted from the gas purifying device 4 to the outside.

During such supply, if the pressure in the gas purifying device 4 is increased to the operating pressure of the laser by the compressor 10, adjustment of the Kr concentration and filling of Ne becomes very easy.

Next, the inlet side valve 5 and the outlet side valve 6 are opened, the opening / closing valve 11 is closed, and a fresh laser gas medium is supplied to the laser main body 2 to start the operation.

The laser gas medium is circulated in the circulation passage 7 and flows into the gas purification device 4, where impurities are removed and the laser gas medium is returned to the laser body 2.

Since Kr is saturated and adsorbed in the portion of the gas purifying device 4, Kr in the circulating gas is in an almost equilibrium state, and as impurities increase, Kr is replaced by impurities and appears on the outlet side. There is no problem if it is within the range of operating conditions.

Furthermore, if necessary, an F
It is also possible to arrange the 2 removal tower 9 (see the phantom line in FIG. 1).

[0045]

As described above, according to the present invention, instead of newly supplying a rare gas such as Kr which is adsorbed in advance on the adsorbent in order to remove impurities, the previous laser oscillation or break-in operation is performed. Since Kr or the like in the exhaust gas due to is reused, expensive Kr or the like can be used without waste.

[0046]

[Brief description of drawings]

FIG. 1 is a graph showing vapor pressures of a laser gas and impurities for explaining the present invention.

[FIG. 2] Similarly, Kr and C at a temperature of minus 81 ° C.
It is a graph which shows the adsorption amount (adsorption equilibrium curve) of activated carbon on F4.

FIG. 3 is a graph showing an adsorption equilibrium curve of CF4 in the presence of Kr.

FIG. 4 is a graph showing adsorption of xenon (Xe) and krypton (Kr) by activated carbon.

FIG. 5 is a graph showing the adsorption of Kr by Columbia CLA activated carbon.

FIG. 6 is a schematic configuration diagram showing an excimer laser 1 equipped with a gas purification device 4 according to an embodiment of the present invention.

[Explanation of symbols]

 1 Excimer laser 2 Laser body including laser tube 3 Circulation pump 4 Gas purification device including adsorption tower 5 Inlet side valve 6 Outlet side valve 7 Circulation passage 8 Exhaust gas supply passage 9 F2 removal tower 10 Compressor 11 Open / close valve

Claims (6)

[Claims] 1. A laser gas medium containing a rare gas,
A gas purification apparatus for excimer laser that performs laser oscillation while circulating between a laser tube and an adsorption tower containing an adsorbent, wherein the adsorbent contained in the adsorption tower has the above-mentioned properties prior to laser oscillation. A gas purifying apparatus for an excimer laser, which is capable of adsorbing a rare gas and uses the rare gas in the gas medium for laser used in the previous laser oscillation as the rare gas to be adsorbed in advance. 2. The gas purifying apparatus for an excimer laser according to claim 1, wherein a halogen removing tower capable of removing halogen in the gas medium for laser is arranged in front of the adsorption tower. 3. The gas purifying apparatus for an excimer laser according to claim 1, wherein the noble gas previously adsorbed on the adsorbent is krypton (Kr). 4. The gas purifying apparatus for an excimer laser according to claim 1, wherein the halogen removing tower is a fluorine gas (F2) removing tower. 5. The gas purifying apparatus for an excimer laser according to claim 1, wherein the adsorption equilibrium pressure of the rare gas adsorbed in advance on the adsorbent and the operating pressure of the buffer gas are filled by a compressor. 6. A laser gas medium containing a rare gas,
A method for purifying a gas of an excimer laser that performs laser oscillation while circulating between a laser tube and an adsorption tower containing an adsorbent, wherein the adsorbent contained in the adsorption tower was used for the previous laser oscillation. The rare gas in the laser gas medium is pre-adsorbed on the adsorbent by passing through the laser gas medium, and then a fresh laser gas medium is supplied to the laser tube to cause laser oscillation. Characteristic excimer laser gas purification method.