JPH0357632B2 - - Google Patents

Description

Detailed Description of the Invention [Object of the Invention] (Field of Industrial Application) The present invention relates to an excimer gas laser oscillation device.

(Prior art) Gas laser oscillation devices include, for example, a rare gas highland excimer laser oscillation device and a CO ₂ laser oscillation device, but the gas laser medium used in these laser oscillation devices generally has several types of gas composition and is used for laser oscillation. Its composition changes each time. For example, Xe: 1% or less, HCl: 0.2% or less, and the rest is He.
Or XeCl using a mixed gas with Ne as the laser medium
In an excimer laser oscillation device that uses a halogen donor as one component in the gas laser medium, the concentration of the halogen donor decreases each time the laser oscillates. When the concentration decreases to 0.1% or less, for example, as shown in FIG. 4, the laser oscillation output sharply decreases. Therefore, in XeCl excimer laser oscillation devices and the like, control is performed so that the halogen donor concentration always remains at a predetermined value in order to reduce the influence of changes in the halogen donor concentration on laser output fluctuations.

Therefore, as a method of controlling output fluctuations due to changes in the halogen donor concentration, a fixed amount halogen injection method and an injection energy increasing method are used.
FIG. 5 is a block diagram of an excimer laser oscillator to which a fixed amount halogen injection method is applied, and a halogen gas cylinder 3 is connected to the excimer laser oscillator 1 via a halogen injection valve 2. Further, an operation shot number counter 4 is provided which counts each time the laser oscillates, and this count value is sent to the injection controller 5. The injection controller 4 has a function of supplying a fixed amount of halogen donor to the excimer laser oscillator 1 by sending an opening operation signal to the halogen injection valve 2 when the number of operating shots reaches a predetermined number. Note that 6 is a high voltage power supply that applies a high voltage between each main discharge electrode of the excimer laser oscillator 1. However, when the halogen donor is not supplied, the halogen donor concentration gradually decreases and the laser output gradually decreases each time the laser oscillates, as shown in FIG.
Then, when the number of operating shots reaches a predetermined value,
The halogen injection valve 2 is opened and halogen donor is supplied to the excimer laser oscillator 1. However,
At this time, as the concentration of the halogen donor increases, the laser output also increases.

FIG. 7 is a block diagram of an excimer laser oscillation device to which the injection energy increasing method is applied, in which the injection controller 7 generates a signal from the high voltage power source 6 between each main discharge electrode in response to an increase in the count value of the operating shot number counter 4. It has a function of highly controlling the applied voltage level. In other words, as shown in FIG. 8, as the number of operating shots increases, the voltage level applied between each main discharge electrode, that is, the injection energy increases.
The laser output is kept constant.

However, each of the above methods has the following problems. First, in the fixed amount halogen injection method, the halogen donor is supplied intermittently, so the halogen donor concentration fluctuates within a certain range, as shown in Figure 6, and as a result, the laser output fluctuates and becomes unstable. There is. Furthermore, in this method, the amount of halogen donor to be injected for each injection is determined by experience, so it cannot cope with large changes in operating conditions, such as when the laser output is changed significantly. In particular, since this method does not directly detect the halogen donor concentration, the reliability of controlling the halogen donor concentration is low.

Furthermore, since the injection energy increasing method forcibly increases the voltage level applied between each main discharge electrode, it is not possible to oscillate laser light under optimal operating conditions. Therefore, as the number of laser oscillations increases, the applied voltage increases, which shortens the life of the laser oscillation device, reduces stability and reliability, and also reduces the efficiency of laser oscillation. descend.

Note that, in practice, the halogen donor concentration and laser output are controlled by combining the above methods, but even if they are combined, the above problems still occur.

(Problem to be Solved by the Invention) As described above, methods have been used to control the halogen toner concentration, that is, the composition of the gas laser medium or the laser output, to a constant value, but as described above, the halogen donor concentration can always be controlled to a predetermined value. Moreover, the life span, stability, and reliability of the laser oscillation device were reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly stable and reliable excimer gas laser oscillation device that can control the composition ratio of a gas laser medium to always be at a predetermined value.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a gas laser oscillation system in which an excimer gas laser medium is sealed in a gas laser tube and a main discharge is generated between main discharge electrodes disposed facing each other in the gas laser tube to oscillate a laser. The device includes a light emitting element that irradiates the inside of the gas laser tube with light of a wavelength in the optical absorption band of the halogen donor that composes the gas laser medium, and a light emitting element that receives the irradiated light and converts it into an electrical signal according to the amount of light received. The above-mentioned device comprises a light receiving element and a gas supply control means for receiving an electric signal from the light receiving element and controlling the amount of halogen donor supplied to the gas laser tube so that the concentration of the halogen donor in the gas laser tube becomes a predetermined value. This is an excimer gas laser oscillation device that aims to achieve this goal.

(Function) By providing such a means, light having a wavelength in the light absorption band of the halogen donor that composes the excimer gas laser medium is emitted from the light emitting element, and this light is received by the light receiving element and is adjusted according to the amount of light received. converted into an electrical signal. Then, in response to the electric signal from the light receiving element, the gas supply control means controls the amount of halogen donor supplied to the gas laser tube so that the concentration of the halogen donor within the gas laser tube becomes a predetermined value.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram of an excimer gas laser oscillation device, in which an excimer having a halogen donor as a part of its composition is sealed inside a gas laser tube 10 as a gas laser medium. Furthermore, main discharge electrodes 11 and 12 are provided inside the gas laser tube 10 and are arranged opposite each other, and an optical resonator is provided at each end of each of the main discharge electrodes 11 and 12 in the longitudinal direction. Total reflection mirror 1
3 and an output mirror 14 are provided. In addition,
A high-voltage power supply 15 is connected between each main discharge electrode 11 and 12 to apply a DC high voltage +HV. Further, a halogen gas cylinder 1 is connected to the gas laser tube 10 via a halogen injection valve 16.
7 is connected.

A diode laser 20 as a light emitting element is provided at one end of the gas laser tube 10 in the longitudinal direction, and its light emission is controlled by a diode laser controller 21. The diode laser 20 has an emission wavelength in the light absorption band of the halogen donor.
When HCl is used as a halogen donor like a XeCl excimer laser, the wave number is set to 5664 to 8347 cm ^-1 . A Pbs semiconductor cell 22 as a light receiving element is provided at the other end of the gas laser tube 10 in the longitudinal direction, that is, at a position facing the diode laser 20. This Pbs semiconductor cell 22 receives diode laser light emitted from the diode laser 20 and traveling through the excimer atmosphere, and outputs an electrical signal of a voltage level corresponding to the amount of received light. This electrical signal is then sent to the concentration controller 23. This concentration controller 23 receives an electric signal from the Pbs semiconductor cell 22, determines the current halogen donor concentration from the voltage level, compares this concentration with a reference concentration, and determines the opening degree so that the halogen donor concentration becomes the reference concentration. It has a function of sequentially sending operation signals to the halogen injection valve 16.

Next, the operation of the apparatus configured as described above will be explained.

A high voltage is applied between each main discharge electrode 11, 12 from a high voltage power supply 15, and these main discharge electrodes 11, 1
When the main discharge occurs between 2 and 2, the total reflection mirror 13
Optical resonance occurs between the output mirror 14 and the output mirror 14, and a laser beam is output from the output mirror 14. When the laser beam is oscillated in this manner, the concentration of the halogen donor gradually decreases as shown in FIG. 4, and the laser output decreases accordingly.

However, in this device, the diode laser controller 21 causes the diode laser 20 to always emit light of the same wavelength as the light absorption band of halogen. However, this diode laser light passes through the gas laser medium and reaches the Pbs semiconductor cell 22. Therefore, while the diode laser light passes through the gas laser medium, a portion of the diode laser light is absorbed depending on the concentration of the halogen donor. However, the Pbs semiconductor cell 22 receives the diode laser light and outputs an electrical signal with a voltage level corresponding to the amount of the received light. This electric signal is sent to the concentration controller 23, which determines the halogen donor concentration from the voltage level of the electric signal, compares it with the reference concentration, and sends an operation signal for the opening such that the halogen donor concentration becomes the reference concentration. It is prepared and sent to the halogen injection valve 16. As a result, the concentration of the halogen donor constituting the gas laser medium is always controlled to a predetermined value. Figure 2 shows the halogen donor concentration and laser output when the halogen donor concentration is controlled as described above.The halogen donor concentration is always constant, and the laser output at that time varies depending on the number of operating shots. It remains almost constant even when the value exceeds ¹⁰⁵ . Furthermore, when looking at the efficiency of laser oscillation, as shown in FIG. 3, it can be seen that the present apparatus is highly efficient compared to the fixed amount halogen injection method and the injection energy increasing method.

In this way, in the above embodiment, the diode laser 20 irradiates light with a wavelength in the optical absorption band of the halogen donor that composes the gas laser medium, and this light is received by the Pbs semiconductor cell 22, and depending on the amount of light received. Since the concentration controller 23 is configured to control the amount of halogen donor supplied to the gas laser tube 10, the halogen donor concentration can be constantly monitored, and when the concentration decreases, halogen donor is supplied to remove the halogen. Donor concentration can be maintained at a predetermined value. Therefore, the laser output can always be kept stable regardless of the number of laser oscillations. Furthermore, since the halogen concentration is measured using the light emitted by the diode laser 20, the measurement does not affect the inside of the gas laser tube 10, such as gas contamination. You can easily prevent problems such as corrosion.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to provide a highly stable and highly reliable excimer gas laser oscillation device that can control the composition ratio of the excimer gas laser medium to always be at a predetermined value.

[Brief explanation of drawings]

1 to 3 are diagrams for explaining one embodiment of an excimer gas laser oscillation device according to the present invention, in which FIG. 1 is an overall configuration diagram, and FIG. 2 is a diagram showing the halogen donor concentration and the number of operating shots. FIG. 3 is a diagram showing the laser output, FIG. 3 is a diagram showing the efficiency with respect to the number of operating shots, FIG. 4 is a diagram showing the laser output with respect to the halogen donor concentration, and FIGS. 5 to 8 are diagrams for explaining the conventional technology. be. 10... Gas laser tube, 11, 12... Main discharge electrode, 13... Total reflection mirror, 14... Output mirror, 15... High voltage power supply, 16... Halogen injection valve, 17... Halogen gas cylinder, 20... Diode laser, 21... diode laser controller, 22... Pbs semiconductor cell, 23... concentration controller.

Claims (1)

[Claims] 1. In an excimer gas laser oscillation device that encloses an excimer gas laser medium in a gas laser tube and generates a main discharge between main discharge electrodes arranged oppositely in the gas laser tube to oscillate the laser, the optical absorption band of the halogen donor that composes the gas laser medium a light emitting element that irradiates light of a wavelength within the gas laser tube; a light receiving element that receives the light irradiated by the light emitting element and converts it into an electrical signal according to the amount of received light; and a light receiving element that receives the electrical signal from the light receiving element. 1. An excimer gas laser oscillation device comprising: gas supply control means for controlling the amount of halogen donor supplied to the gas laser tube so that the concentration of the halogen donor in the gas laser tube becomes a predetermined value.