JPS63288078A - Oscillator for excimer laser - Google Patents

Abstract

PURPOSE:To oscillate an excimer laser at long pulses with high efficiency by composing a secondary side capacitor for a discharge excitation circuit of a plurality of pulse shaping capacitors mutually connected in parallel. CONSTITUTION:When a primary side capacitor C1 is charged by negative high voltage-HV and a trigger Tr is applied to a high-voltage switch SW and the switch SW is closed, high voltage is applied to a main discharge electrode 2 while all pulse shaping capacitors C2p, C2p... for secondary side capacitors C2, C2 are charged simultaneously. Consequently, high voltage is applied to pre-ionization electrodes 3 and discharge is generated, and ultraviolet rays are generated. An excimer laser medium is pre-ionized by the ultraviolet rays, thus generating main discharge in a main discharge section 21. The excimer laser medium is excited by the main discharge, and an excimer laser is oscillated. The secondary side capacitors C2 are composed of pulse shaping circuits having characteristics close to a distributed constant circuit by the four pulse shaping capacitors C2p, C2p..., thus changing the oscillation of the excimer laser into long pulses.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a device for oscillating an excimer laser with high efficiency in one long pulse.

<Prior art> Excimer lasers, which are high-output lasers in the ultraviolet region that use gas as a laser medium, have short pulse oscillations and therefore have low car coloring, and are used, for example, as excitation light sources for isotope separation or semiconductors. It was inconvenient to use for processing. Therefore, various attempts have been made to increase the length of the excimer laser oscillation pulse.

In order to make the oscillation of a discharge-excited excimer laser into a longer pulse, that is, to lengthen the oscillation time, it is sufficient to lengthen the excitation discharge time, but if the pulse is made longer, the oscillation efficiency generally decreases.

Therefore, conventionally, in order to lengthen the excitation discharge time without reducing the efficiency, an oscillating tube as shown in the block diagram of FIG. 3 has been used. That is, this oscillation device is provided with a main discharge electrode 2 and a pair of pre-ionization electrodes 3.3 above and below the main discharge electrode 2 inside a laser tube l which encloses an excimer laser medium of Xecl hg. A discharge excitation circuit EX is connected to the main discharge electrode 2 and the preliminary ionization electrode 3.3. By charging C3 with a positive high voltage +IIV and closing the high voltage switch S+a, the capacitance is transferred from the negative side capacitor C1 to the secondary side capacitors C2, C, and preionization is performed at the preionization electrode 3.3. At the same time, the main discharge is caused to occur at the main discharge electrode 2. This excites the excimer laser medium to oscillate a laser.

In the above oscillation device, the anode '- of the main discharge electrode 2 is
[An additional coil La is connected in series with the pole AE, and the inductance of the additional coil La extends the duration of the main discharge to lengthen the laser oscillation time, that is, to make the pulse longer.

<Problems to be solved by the invention> However, as mentioned above, with the conventional wrinkle generating device provided with the additional coil La, it is not possible to achieve a sufficiently long pulse, and
For fluorine-based excimer laser media such as rF, there is a problem that a main discharge cannot be caused, that is, a laser cannot be oscillated.

Means for Solving the Problems> The present invention is an excimer proposed to solve the above problems.
This laser oscillation device is characterized in that the secondary capacitor of the discharge excitation circuit is composed of a plurality of pulse shaping capacitors connected in parallel with each other.

Effects> The above configuration increases the duration of discharge at the preliminary gI electrode. Therefore, the duration of the main discharge is extended as well as the pre-ionization, and the oscillation of the excimer laser becomes a longer pulse and becomes more efficient.

(Example) Hereinafter, the present invention will be described in detail based on the drawings.The same numbers and symbols will be used for components that are the same as in the conventional example.

FIG. 1 is a block diagram illustrating an oscillation device for an excimer laser according to the present invention, and a laser tube 1 in the figure is shown in a schematic vertical cross-sectional view.

As shown in the figure, this oscillation device is composed of a laser tube l filled with an excimer laser medium such as XeCl, and a discharge excitation circuit EC connected to a high voltage type (not shown). Inside the laser tube l, there are a main discharge electrode 2 consisting of a rod-shaped anode electrode ^E and a cathode electrode E horizontally opposed to each other, and a pair of preliminary ionization electrodes 3.3 above and below the main discharge electrode 2. It is provided. The size of the main discharge part 21 formed between the anode electrode AE and the cathode electrode KE of the main discharge part ai2 is, for example, a radius Q of 6 cm, a height of 2620 mm, and a length of 60 cm. The pre-ionization electrode 3 forms a pin gap PG with a single pin 31 attached above and below the laser tube l and a common pin 2 connected to the cathode electrode KE, and is mainly used for pre-ionization, which will be described later. A plurality of pairs, for example 13 pairs, are provided at equal intervals along the main discharge electrode 2 so that discharge can be performed uniformly in the discharge section 21. Both front and rear ends of the laser tube 1 are closed with fused silica Brewster windows (not shown).

On the other hand, the discharge excitation circuit EC is connected to each of the above-mentioned spare electrodes 3
Each discharge excitation circuit EC has a configuration as shown in FIG. That is, one end of the negative side capacitor CI is connected to a high voltage power supply via a resistor R0, and is also grounded via a high voltage switch SW such as a thyratron. Further, the other end of the next-side capacitor C1 is connected to the anode electrode AE of the main discharge electrode 2, and has a high resistance R2.
is grounded through. The cathode electrode KE of the main discharge electrode 2 is grounded.

And - next side capacitor C1 and upper and lower pre-ionization electrodes 3
, 3 are secondary capacitors C*, C with the same capacity, respectively.
Connected by 2. Furthermore, each secondary side capacitor 0
2 is configured to have characteristics close to a distributed constant circuit by a plurality of, for example, four, pulse shaping capacitors c2p, c, p, . . . connected in parallel with each other. A circuit consisting of these pulse shaping capacitors C29, c2p-, etc. is called a pulse shaping circuit. Also, secondary side capacitor C
2 capacitance, i.e. four pulse shaping capacitors C2p,
The combined capacitance of Czp... is approximately equal to the capacitance of the negative side capacitor C.

With the two-leg configuration, the negative side capacitor C is charged with a negative high voltage of -11V, and the trigger T is applied to the high voltage switch SW.
When r is applied and closed, a high voltage is applied to the main electrode 2, and the charge is transferred to the secondary capacitors C2, C2, and all the pulse shaping capacitors c2p, C2p, etc. of the secondary capacitors C2, C2 are connected.・are charged at the same time. That is, the capacitance is transferred from the secondary capacitor C2 to the secondary capacitors C2, C2.

Then, a high voltage is applied to the pre-ionization electrode 3, causing a discharge, and the discharge generates ultraviolet rays. and excimer
As the laser medium is heated by this ultraviolet ray, a 1-hour sleep occurs in the main discharge section 21. This main discharge excites the excimer laser medium and oscillates an excimer laser.

The above-mentioned oscillation process is intermittently repeated by opening and closing the high voltage switch SW, so that the excimer laser is oscillated in a pulsed manner.

In the above oscillation process, the secondary capacitor 02 or the four pulse shaping capacitors C2p.

Since it is composed of a pulse shaping circuit that has characteristics similar to a distributed constant circuit due to C2p..., the discharge from the four pulse shaping capacitors C29, C29... is not simultaneous, but on the preliminary type a electrode 3 side. The discharge occurs with a slight shift in order from 1 to 3, and as a result, the duration of the discharge at the pre-ionization electrode 3 becomes longer. Therefore, the duration of the main discharge is extended along with pre-ionization, and the oscillation of the excimer laser is made into a long pulse. Moreover, pulse shaping capacitor C21), C2p
Since the pulse shaping circuit consisting of
It can oscillate with high efficiency.

The oscillation device with the above configuration generates an excimer laser using Xecl as a medium with an efficiency of 2% and a pulse width of 68 nsec.
It was possible to oscillate at (full width at half maximum).

Further, as shown in the configuration diagram of FIG. 2, a pulse shaping capacitor Czl) is connected to the preionization electrode 3.

By inserting a pulse shaping coil tp between the first stage and the second stage from the pre-ionization electrode 3 side of the cap...
The duration of f@ionization can be made longer, ie the pulse of oscillation can be made longer. With this configuration, pulse @90
It was possible to oscillate at nsec (full width at half maximum).

Furthermore, by increasing the number of pulse shaping capacitors C2p, C2p, . . . that constitute the secondary side capacitor C2, it is possible to make the oscillation into a longer pulse. Furthermore, the oscillation device of the present invention can oscillate even in a fluorine-based excimer laser medium.

<Effects of the Invention> As described above, according to the oscillation device of the present invention, the excimer
Lasers can be oscillated with long pulses and with high efficiency, and the type of excimer laser medium is not limited. Therefore, excimer lasers can be used as excitation light sources for isotope separation and semiconductor processing, etc. This will greatly contribute to expanding the range of applications.

[Brief explanation of the drawing]

Fig. 1 is a block diagram explaining an excimer laser oscillation device according to the present invention, Fig. 2 is a block diagram explaining another embodiment of the excimer laser oscillation device according to the present invention, and Fig. 3 is a block diagram explaining a conventional oscillation device. FIG. l... Laser tube, 2... Main discharge electrode. 3...T-ionization electrode, EC...discharge excitation circuit. Ct...-Next side capacitor. C2...Secondary side capacitor. C2p--Pulse shaping capacitor. Patent Applicant Kei Sasaki Yasushi Sukehorinouchi Agent Patent Attorney Kuninori Funatachibana Figure 1 Figure 2

Claims (1)

[Claims] A laser tube is provided with a main discharge electrode and a pre-ionization electrode inside which encloses an excimer laser medium, and the capacitance is transferred from a charged primary capacitor to a secondary capacitor, and pre-ionization is performed at the pre-ionization electrode. In an excimer laser oscillation device comprising a discharge excitation circuit that causes a main discharge at the main discharge electrode, a secondary capacitor of the discharge excitation circuit is constituted by a plurality of pulse shaping capacitors connected in parallel with each other. An excimer laser oscillation device characterized by: