JP2009194063A - Discharge excitation type gas laser apparatus and fault location determination method thereof - Google Patents

Abstract

【Task】
It is possible to safely and quickly determine which of the pulse power module and the laser chamber is malfunctioning.
[Solution]
A current sensor detects a current flowing between a peaking capacitor of a discharge circuit formed in the laser chamber and a magnetic pulse compression circuit formed in the pulse power module.
[Selection] Figure 2

Description

  The present invention relates to a discharge-excited gas laser device in which a current sensor is provided between a peaking capacitor provided in a laser chamber and a magnetic pulse compression circuit provided in a pulse power module, and using a measurement value of the current sensor. The present invention relates to a failure location determination method for determining which of a laser chamber and a pulse power module has failed.

  With the miniaturization and high integration of semiconductor integrated circuits, improvement in resolving power is demanded in the projection exposure apparatus for production. For this reason, the wavelength of the exposure light emitted from the exposure light source is being shortened, and a KrF excimer laser device having a wavelength of 248 nm from a conventional mercury lamp is used as a light source for semiconductor exposure. Further, as a next-generation light source for semiconductor exposure, gas laser devices that emit ultraviolet rays, such as an ArF excimer laser device having a wavelength of 193 nm and a fluorine (F2) laser device having a wavelength of 157 nm, are promising.

  In the KrF excimer laser apparatus, a mixed gas composed of a rare gas such as fluorine (F2) gas, krypton (Kr) gas and neon (Ne) as a buffer gas is used as the laser gas. In the ArF excimer laser device, a mixed gas comprising a rare gas such as fluorine (F2) gas, argon (Ar) gas and neon (Ne) as a buffer gas is used as the laser gas. In the fluorine (F2) laser apparatus, a mixed gas comprising fluorine (F2) gas and a rare gas such as helium (He) as a buffer gas is used as the laser gas. In each laser apparatus, the laser gas is enclosed in a laser chamber at several hundred KPa.

  Inside the laser chamber, a discharge circuit including a pair of main discharge electrodes and a peaking capacitor connected in parallel to the main discharge electrodes is formed. A pulse power module is mechanically connected to the laser chamber, and a magnetic pulse compression circuit electrically connected to the discharge circuit of the laser chamber is formed inside the pulse power module.

  The energy supplied from the charging circuit is pulse-compressed by the magnetic pulse compression circuit, and the energy is transferred to the peaking capacitor of the discharging circuit. When the energy pulse-compressed is transferred to the peaking capacitor, a high voltage is applied to the main discharge electrode. When the voltage applied between the main discharge electrodes reaches a certain value (breakdown voltage), the laser gas between the main discharge electrodes is dielectrically broken to start main discharge, and the laser gas which is a laser medium is excited by this main discharge. Then, a pulsed laser beam is output.

  In such a discharge excitation type gas laser apparatus, when any abnormality occurs in the laser output, for example, when the laser output becomes zero, there is a possibility that either the laser chamber or the pulse power module has failed. is there.

  The pulse power module and the laser chamber handle a very high voltage of several tens of kV and are closely connected so as to have a low inductance, making it difficult to measure a voltage for detecting a failure. If the voltage measuring device is provided inside the laser device, the laser device itself is increased in size. There are many cases where the installation space of a laser device is limited, and a large laser device is not desirable. Therefore, it has been difficult to specify which of the pulse power module and the laser chamber is out of order.

  When the discharge excitation gas laser device operates, a high voltage of several tens of kV is applied to the magnetic pulse compression circuit and the discharge circuit. For this reason, there is a danger in the inspection in which the laser device is operated in a state where a part of the voltage measuring device such as a high voltage probe is protruded from the window of the casing of the pulse power module as in the prior art. There is also a risk that the contact of the voltage measuring device may be connected to a part other than the connection part of the magnetic pulse compression circuit and the discharge circuit. Furthermore, in such a case, a new failure may be caused.

  The present invention has been made in view of such a situation, and an object of the present invention is to make it possible to safely and quickly determine which of the pulse power module and the laser chamber has failed.

In order to achieve the above object, the first invention provides:
A laser chamber having a main discharge electrode and a peaking capacitor connected in parallel to the main discharge electrode; and a pulse power module having a magnetic pulse compression circuit for pulse-compressing pulse energy supplied from a power source, Discharge excitation in which pulse-compressed energy is transferred from the pulse compression circuit to the peaking capacitor and pulse discharge is generated between the main discharge electrodes, thereby exciting the laser gas sealed in the laser chamber and outputting pulse laser light. In a gas laser device,
A sensor for detecting a current flowing between the peaking capacitor and the pulse power supply circuit is provided.

  In the first invention, a current sensor detects a current flowing between a peaking capacitor of a discharge circuit formed in a laser chamber and a magnetic pulse compression circuit formed in a pulse power module. An output terminal is drawn out from the current sensor, so that an apparatus such as an oscilloscope that can observe current can be easily connected.

The second invention is the first invention,
The sensor is immersed in insulating oil.

  When a current sensor is provided in a space, a certain amount of space is required to ensure insulation from the surroundings. On the other hand, if the current sensor is immersed in insulating oil, a space for securing insulation can be reduced, and a space for installing the current sensor can be reduced. In general, a magnetic pulse compression circuit and a peaking capacitor are placed as close as possible to reduce energy loss during energy transfer. If the installation space of the current sensor for detecting the current is small, it is not necessary to widen the gap between the magnetic pulse compression circuit and the peaking capacitor, and the energy loss does not increase. When the magnetic pulse compression circuit is immersed in insulating oil in the pulse power module, the current sensor may be immersed in the insulating oil together with the magnetic pulse compression circuit.

Also, the third invention is
In the failure location determination method of the discharge excitation gas laser device for determining the failure location of the discharge excitation gas laser device that excites the laser gas by generating a pulse discharge between the main discharge electrodes and outputs laser light,
The discharge excitation gas laser apparatus is
A laser chamber having the main discharge electrode and a peaking capacitor connected in parallel to the main discharge electrode;
A pulse power module having a magnetic pulse compression circuit for compressing pulse energy supplied from a power source and transferring the pulse energy to the peaking capacitor;
A sensor for detecting a current flowing between the peaking capacitor and the magnetic pulse compression circuit,
Measure current with the sensor,
If the measured value is a normal value, it is determined that the laser chamber is faulty. If the measured value is an abnormal value, it is determined that the pulse power module is faulty.

  The third invention is a method for discriminating which of the laser chamber and the pulse power module has failed using the current sensor of the first invention.

  If the measured value of the current sensor is within the normal value range, it can be determined that there is no failure in the pulse power module on the upstream side of the current sensor and that the laser chamber on the downstream side of the current sensor has a failure. On the contrary, if the measured value of the current sensor is within the range of the abnormal value, it can be determined that there is a failure in the pulse power module on the upstream side of the current sensor and that there is no failure in the laser chamber on the downstream side of the current sensor.

  According to the present invention, the current sensor is provided between the magnetic pulse compression circuit and the peaking capacitor of the discharge circuit. The current sensor is smaller than a voltage measuring device such as a high voltage probe, and the laser device including the current sensor is not as large as the laser device including the voltage measuring device. If the current sensor is provided in advance in the laser device, the work at the time of failure inspection only needs to confirm the measured value of the current sensor with an external device, the work itself is easy and does not involve dangerous work. .

  Furthermore, according to this invention, the installation space of a current sensor itself and a current sensor can be reduced in size by immersing a current sensor in insulating oil.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a mechanical connection relationship between a laser chamber and a pulse charger. FIG. 2 is a diagram showing a connection relationship between the discharge circuit in the laser chamber and the magnetic pulse compression circuit in the pulse power module.
As shown in FIG. 1, a laser gas is sealed inside the laser chamber 10, and a discharge circuit 11 including a pair of main discharge electrodes 12, 13 and a peaking capacitor Cp is formed. The pair of main discharge electrodes 12 and 13 includes an anode and a cathode, and the anode and the cathode are arranged so that the longitudinal directions thereof are parallel to each other, the discharge surfaces are opposed to each other, and are separated by a predetermined distance. A pulse power module 20 is connected to the laser chamber 10. A tank 23 filled with insulating oil 22 is provided inside the pulse power module 20, and the magnetic pulse compression circuit 21 and the current sensor 42 are immersed in the insulating oil 22. The laser chamber 10 and the pulse power module 20 are modularized.

  The magnetic pulse compression circuit 21 of the pulse power module 20 and the discharge circuit 11 of the laser chamber 10 are configured as shown in FIG. In the circuit shown in FIG. 2, the discharge circuit 11 is provided inside the laser chamber 10, and the magnetic pulse compression circuit 21, the step-up transformer T, the solid state switch SW, the magnetic assist SR1, the main capacitor C0, and the current sensor 42 have pulse power. Provided inside the module 20, the charging circuit 31 is provided inside the charger 30. The discharge circuit 11 is provided with main electrodes 12 and 13 and a peaking capacitor Cp, and the magnetic pulse compression circuit 21 is provided with transfer capacitors C1 and C2 and magnetic switches SR2 and SR3.

A peaking capacitor Cp is connected to the main discharge electrodes 12 and 13 in parallel. A series circuit including a magnetic switch SR3 and a transfer capacitor C2 is connected in parallel to the peaking capacitor Cp. A series circuit including the magnetic switch SR2 and the transfer capacitor C1 is connected in parallel to the transfer capacitor C2. A secondary winding T2 of a step-up transformer T is connected in parallel to the transfer capacitor C1.
On the other hand, a main capacitor C 0 is connected in parallel to the output terminal of the charging circuit 31. A series circuit composed of a magnetic assist SR1, a primary winding T1 of a step-up transformer T, and a solid switch SW is connected to the main capacitor C0 in parallel.

  In the circuit shown in FIG. 2, a current sensor 42 is provided in the wiring 41 that electrically connects the magnetic pulse compression circuit 21 and the discharge circuit 11. The current detection sensor 42 may be any sensor as long as it can detect the current flowing from the magnetic pulse compression circuit 21 to the discharge circuit 11, and the form is not limited. As an example of the current sensor 42, there is a Hall element type current sensor in which a Hall element and a ring-shaped magnetic core having a notch in part are combined. In the present embodiment, the current sensor 42 is provided in such a form that the wiring 41 is inserted through an annular magnetic core. The current sensor 42 is immersed in the insulating oil 22 in the pulse power module 20 together with the magnetic pulse compression circuit 21, but may not be immersed in the insulating oil 22. In this embodiment, the pulse power module 20 is provided, but may be provided in the laser chamber 10. The current sensor 42 has an output terminal 42 a outside the pulse power module 20. A device for observing current, such as an oscilloscope, can be connected to the output terminal 42a.

FIG. 3 is a diagram showing the overall flow of the failure determination process in the present embodiment.
When an abnormality is detected in the laser output and it is determined that the cause is in the circuit system (step 01), laser oscillation for failure determination similar to normal laser oscillation is performed as follows.

  When energy is transferred from the transfer capacitor C2 to the peaking capacitor Cp, the current flowing through the wiring 41 is detected by the current sensor 42 (step 02). The worker checks the measured value of the current sensor 42 with an oscilloscope connected to the output terminal 42a.

  If the measured value of the current sensor 42 is within the normal value range, there is no abnormality in the current flowing through the wiring 41 (YES at step 03). That is, it can be determined that there is no failure in the pulse power module 20 on the upstream side of the current sensor 42 and that there is a failure in the laser chamber 10 on the downstream side of the current sensor 42 (step 04). The operator removes the laser chamber 10 from the laser device, and newly installs a replacement laser chamber 10 to restore the laser device. The removed laser chamber 10 is reused as a replacement laser chamber 10 after repairing the failed part.

  If the measured value of the current sensor 42 is within the abnormal value range, the current flowing through the wiring 41 is abnormal (NO at step 03). That is, it can be determined that there is a failure in the pulse power module 20 on the upstream side of the current sensor 42 and that there is no failure in the laser chamber 10 on the downstream side of the current sensor 42 (step 05). The worker removes the pulse power module 20 from the laser device, and newly installs a replacement pulse power module 20 to restore the laser device. The removed pulse power module 20 is reused as a replacement pulse power module 20 after repairing the failed part.

  According to this embodiment, the current sensor is provided between the magnetic pulse compression circuit and the peaking capacitor of the discharge circuit. The current sensor is smaller than a voltage measuring device such as a high voltage probe, and the laser device including the current sensor is not as large as the laser device including the voltage measuring device. If the current sensor is provided in advance in the laser device, the work at the time of failure inspection only needs to confirm the measured value of the current sensor with an external device, the work itself is easy and does not involve dangerous work. .

  Furthermore, according to this embodiment, the installation space of the current sensor itself and the current sensor can be reduced in size by immersing the current sensor in the insulating oil.

The figure which shows the mechanical connection relationship of a laser chamber and a pulse charger. The figure which shows the connection relation of the discharge circuit in a laser chamber, and the magnetic pulse compression circuit in a pulse power module. The figure which shows the whole flow of the failure judgment process in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Laser chamber, 11 ... Discharge circuit, 12, 13 ... Main discharge electrode groove,
20 ... pulse power module, 21 ... magnetic pulse compression circuit,
30 ... charger, 31 ... charging circuit,
41 ... Wiring, 42 ... Current sensor Cp ... Peaking capacitor

Claims (3)

A laser chamber having a main discharge electrode and a peaking capacitor connected in parallel to the main discharge electrode; and a pulse power module having a magnetic pulse compression circuit for pulse-compressing pulse energy supplied from a power source, Discharge excitation in which pulse-compressed energy is transferred from the pulse compression circuit to the peaking capacitor and pulse discharge is generated between the main discharge electrodes, thereby exciting the laser gas sealed in the laser chamber and outputting pulse laser light. In a gas laser device,
A discharge-excited gas laser device comprising a sensor for detecting a current flowing between the peaking capacitor and the pulse power supply circuit. The discharge excitation type gas laser device according to claim 1, wherein the sensor is immersed in insulating oil. In the failure location determination method of the discharge excitation gas laser device for determining the failure location of the discharge excitation gas laser device that excites the laser gas by generating a pulse discharge between the main discharge electrodes and outputs laser light,
The discharge excitation gas laser apparatus is
A laser chamber having the main discharge electrode and a peaking capacitor connected in parallel to the main discharge electrode;
A pulse power module having a magnetic pulse compression circuit for compressing pulse energy supplied from a power source and transferring the pulse energy to the peaking capacitor;
A sensor for detecting a current flowing between the peaking capacitor and the magnetic pulse compression circuit,
Measure current with the sensor,
If the measured value is a normal value, it is determined that the laser chamber has failed, and if the measured value is an abnormal value, it is determined that the pulse power module has failed. Fault location method.

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