JPS6327084A - Laser apparatus with differential pressure cell - Google Patents

Abstract

PURPOSE:To reduce the number of stages of a sealing unit by providing a differential pressure cell separately through a partition wall from a laser gas chamber, projecting the driving shaft of a laser gas circulation fan into the cell, and providing a magnetic fluid seal at a part passing the partition wall. CONSTITUTION:A laser gas circulation fan 10 is rotated by a driving system 16 provided in a differential pressure cell 13 to circulate laser gas cooled in a main discharge area. Since the differential pressure between the pressure in a laser gas chamber 11 and the pressure in the cell 13 is smaller than that between the chamber 11 and the atmospheric pressure, a shaft can be sealed with a magnetic fluid sealer 14 of less number of stages. A motor 16 which forms a driving system is provided in the cell 13, and directly coupled with a driving shaft 15 projected from the sealer 14.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Application Field The present invention relates to a laser device, such as an excimer laser device, in which laser gas sealed in a laser gas chamber under high pressure is circulated by a built-in fan. be.

B. Prior Art In FIGS. 2 and 3 showing a conventional excimer laser device, a laser gas circulation fan 2. Heat exchanger 3. Main discharge electrodes 4, 5. A peaking capacitor 6 is built-in. Because laser gas is corrosive.

A driving motor 16 for the laser gas circulation fan 2 is placed outside the laser gas chamber 1, as shown in FIG. That is, the shaft 2a of the laser gas circulation fan 2 protruding to the outside of the laser gas chamber 1 passes through the magnetic fluid sealing device 14 in which multiple stages of pole pieces are built, and connects to the pulley 7 at the tip and the output shaft of the drive motor 16. Boo set up! A timing belt 9 is passed between the timing belt J8 and the laser gas circulation fan 2, thereby driving the laser gas circulation fan 2.

In such a conventional excimer laser device, when a discharge occurs between the main discharge electrodes 4 and 5 due to the high voltage applied from the high voltage control circuit, the laser gas in this region deteriorates, so the laser gas circulation fan 2 While circulating the laser gas, the heat exchanger 3 cools the laser gas whose temperature has increased due to discharge excitation.

In addition, in recent years, laser oscillations have tended to have higher repetition rates, and accordingly, the rotation speed of the laser gas circulation fan 2 has also been increased to 1, for example, 3000 to 4000 rpm for 1007 oscillations.
, and a magnetic fluid feedthrough is essential as a shaft sealing member.

C6 Problems to be Solved by the Invention In a pressurized laser device such as the excimer laser device described above, the differential pressure between the internal pressure of the laser gas chamber 1 and the atmosphere is large, so the magnetic fluid seal group [14 refers to the number of stages of the pole piece set to a vacuum. The magnetic fluid seal device has to be larger than the one for the equipment, and the size of the magnetic fluid seal device increases, and the entire laser device also increases in size.Furthermore, the magnetic fluid seal device has a large torque loss, and if it is multi-staged, the size of the laser device increases. The motor must be large and have a high output, and the magnetic fluid sealing device is expensive, and if it is large and has multiple stages, the cost of the laser device will increase.

Further, since friction powder is generated due to friction between the timing belt and the pulley, it is not desirable to use this type of drive system as a light source for a semiconductor exposure apparatus in a place where dust and the like are not desired, such as a semiconductor manufacturing factory.

An object of the present invention is to solve the above problems and provide a compact laser device having a laser gas circulation fan drive system using a small magnetic fluid seal device with a small number of stages.

Means for solving the D0 problem This problem is solved by the laser gas chamber 11 and the partition wall 12.
A differential pressure cell 13 is provided across the laser gas circulation fan 1.
The drive shaft 15 of 0 passes through the partition wall 12 and protrudes into the differential pressure cell 13, and a magnetic fluid sealing device 14 for sealing the laser gas in the laser gas chamber 11 is provided at the portion where the drive shaft 15 penetrates the partition wall 12. This problem is solved by a laser device in which a drive system 16 for supplying power to a drive shaft 15 is provided inside the differential pressure cell 13.

80 operation laser gas circulation fan 10 is rotated by a drive system 16 provided within the differential pressure cell 13 and circulates cooled laser gas to the main discharge area. Laser gas chamber 11
Since the pressure difference between the pressure inside the laser gas chamber 11 and the pressure inside the differential pressure cell 13 is smaller than the pressure difference between the inside of the laser gas chamber 11 and the atmosphere,
The shaft can be sealed using a magnetic fluid sealing device with fewer stages than conventional ones.

F. Embodiment FIG. 1 shows a driving section of a laser gas circulation fan when the present invention is applied to an excimer laser device.

A differential pressure cell 13 is provided adjacent to a laser gas chamber 11 in which a laser gas circulation fan 10 is built, with a partition wall 12 in between. A magnetic fluid sealing device 14 is provided through the partition wall 12 , and a drive shaft 15 of the laser gas circulation fan 10 passes through the magnetic fluid sealing device 14 and projects into the differential pressure cell 13 . Magnetic fluid seal group [14 is the flange part 1
4a is fixed to the partition wall 12 via an O-ring or the like, and the partition wall through-hole is sealed at that portion.

The built-in magnetic fluid seals the drive shaft 15 in a well-known manner.

A motor 16 constituting a drive system is provided within the differential pressure cell 13, and a drive shaft 15 protrudes from the magnetic fluid sealing device 14.
are directly connected. In this embodiment, in order to achieve miniaturization, a brushless DC motor is used which is thin, capable of torque control, and capable of continuous operation even at high speeds.

Note that the rotational force of the motor 15 may be transmitted to the laser gas circulation fan IO through an appropriate power transmission mechanism such as a gear end. 17 is a bearing.

The laser gas chamber 11 contains an active gas and a rare gas (Ar) in the case of a halide excimer laser.

Kr, Xe) supply pipe 21 and buffer gas supply pipe 22
A branch pipe 22a of the exhaust pipe 23 is connected to the differential pressure cell 13, and a buffer gas supply pipe 22 and a branch pipe 23a of the exhaust pipe 23 are connected to the differential pressure cell 13.
During operation, the laser gas chamber 11 contains an active gas such as F2 and HCI, and a rare gas such as Ar, Kr, and Xs. A buffer gas (rare gas) typified by He''P Ne is sealed under a pressure of 2 to 3 atmospheres, and only the bathophore gas, which is an inert gas, is sealed in the differential pressure cell 13 under a pressure slightly higher than that in the laser gas chamber 11. Note that check valves 28 and 29 are provided in the buffer gas branch pipe 22a and the exhaust branch pipe 23a.

Backflow from the laser gas chamber 11 to the differential pressure cell 13 is prevented (note that the check valve symbol in Figure 1 means that gas flows only towards the top of the triangle). Further, the exhaust branch pipe 23a has a conductance smaller than that of the exhaust pipe 23, so that a pressure difference is formed between the laser gas chamber 11 and the differential pressure cell 13 even during exhaust.

In the excimer laser device having the above configuration, a procedure for filling gas at a predetermined pressure into the laser gas chamber 11 and the differential pressure cell 13 will be explained.

First, the case of evacuating the inside of the laser gas chamber 11 and the differential pressure cell 13 will be explained. When the electromagnetic valve 25 is opened without driving the vacuum pump (not shown), the pressurized gas in the laser gas chamber 11 and the differential pressure cell 13 will be evacuated. It is released using the pressure difference with atmospheric pressure. After that, when the vacuum pump is driven to evacuate the chamber 11 and the differential pressure cell 13, since the conductance of the pipe is smaller in the branch pipe 23a, the ultimate pressure is higher in the differential pressure cell 13, and therefore the differential pressure cell 13 is lowered. The pressure in the pressure cell 13 is higher than the pressure in the chamber 11. This pressure difference is caused by Ar, Kr,
It is set higher than the total gas pressure in the chamber 11 when a rare gas such as Xe is introduced. After completing the predetermined evacuation, the solenoid valve 25 is closed.

Next, the laser gas is supplied, but first the solenoid valve 24 is opened and the active gas supply pipe 21 is supplied to the laser gas chamber 11.
Supply active gas to. Furthermore, in the case of a rare gas halide excimer laser, a rare gas such as Ar, Kr, or Xe is introduced. At this time, the total pressure of the gas introduced into the laser gas chamber 11 is 0, which is smaller than the above pressure difference.
．． 27 is opened, and the buffer 7 gas is supplied to the laser gas chamber 1 from the buffer gas supply pipe 22 and its branch pipe 22a.
1 and the differential pressure cell 13, the solenoid valve 27 is closed, and a small amount of buffer gas is additionally supplied only to the differential pressure cell 13. The pressure in the laser gas chamber II is made slightly higher than the pressure in the laser gas chamber II.

By supplying gas into the chamber 11 and the differential pressure cell 13 in this manner, the interior of the differential pressure cell 13 is filled only with inert gas such as He and Ne, and the number of stages of pole pieces of the magnetic fluid seal device can be reduced. , Moreover, the differential pressure cell 13
The motor 16 and the like inside will not be exposed to corrosive active gas.

Furthermore, in this embodiment, since the drive shaft 15 is directly connected to the motor 16 and no radial force is applied, no radial load is applied to the magnetic fluid sealing device, which reduces the service life, which has often been a problem in the past. It can be made longer.

Note that the present invention can also be applied to pressurized gas laser devices other than excimer laser devices.

As described in detail of the G0 invention, according to the laser device according to the present invention, the internal pressure difference between the laser gas chamber and the differential pressure cell is smaller than the difference between the internal pressure of the laser gas chamber and the atmospheric pressure, and the magnetic fluid seal bag is used. Since the pressure difference for sealing becomes smaller,
The number of pole pieces can be reduced, contributing to cost reduction and downsizing. Furthermore, since the torque loss caused by the magnetic fluid seal device is also reduced, the motor output can be reduced, making it possible to downsize the motor, which further contributes to downsizing the entire mm device.

Furthermore, since the drive system is built into the differential pressure cell, dust and the like are not scattered outside the laser device, and the laser device can be used without any problems in semiconductor manufacturing factories and the like where dust is averse.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of a laser gas chamber of a laser device according to the present invention, FIG. 2 is a schematic diagram of an excimer laser device, and FIG. 3 is a partial cross-sectional view of a laser gas chamber of a conventional laser device, showing the laser gas circulation. FIG. 3 is a diagram illustrating a fan drive system. 10: Laser gas circulation fan 11: Laser gas chamber 12: Partition wall 13: Differential pressure cell 14: Magnetic fluid seal device 15: Drive shaft 16: Motor (drive system)

Claims (1)

[Claims] A laser device in which laser gas in a laser gas chamber is circulated by a built-in fan, wherein a differential pressure cell is provided between the laser gas chamber and a partition wall, and a drive shaft of the fan is passed through the partition wall to circulate the laser gas in the differential pressure cell. A magnetic fluid sealing device that protrudes inside and seals the laser gas in the laser gas chamber at a portion where the drive shaft penetrates the partition wall is provided, and a drive system that supplies power to the drive shaft is provided in the differential pressure cell. A laser device equipped with a characteristic differential pressure cell.