JPS6232675A - Laser oscillator - Google Patents

Abstract

PURPOSE:To obtain a pulse laser oscillator characterized by a high output and high efficiency, by inserting a charge current bypass circuit having a switching function in parallel with a preliminary-ionization-electrode pair, which is inserted in a charging circuit for a capacitor. CONSTITUTION:A pulse charging circuit 12, which is driven by a high voltage power source 11, charges a peaking capacitor 3 in a pulse mode. A current bypass circuit 13 acts as a delay circuit for delaying preliminary ionization discharge 5. When the preliminary ionization is started in the charging process of the peaking capacitor in this way, time is required until the main discharge with preliminary ionized electrons as a core is formed. the charging voltage is increased during this period and the charge starting voltage is increased. When the charging voltage to the peaking capacitor 3 is increased, energy inputted to a discharge exciting part 7 is increased, the laser output becomes high and high efficiency is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a laser oscillator, and particularly to a laser oscillator that achieves high output and high efficiency.

[Conventional technology]

Figure 4 shows the conventional excimer tape (for example, ArF,
It is a vertical cross-sectional view showing the configuration of a short pulse laser such as KrF', XeF,
11 is the first main electrode, (2) is the second main electrode, (31 is the peaking capacitor N (4a
), (4b) are a pair of pre-ionizing electrodes for stimulating the pre-ionizing discharge, (5) is the pre-ionizing discharge, (6) is the ultraviolet light emitted from the pre-ionizing discharge, and (7) is the main discharge [therefore, the laser Excited discharge excitation part, (8) laser oscillation optical axis, (9
) is a laser gas, 101 is a laser housing for enclosing the laser gas, (11) is a high-voltage power supply, and Shino is a pulse charging circuit for pulse-charging the beechima capacitor (3).

Next, the operation will be explained. As an example, the case of a KrF laser will be explained. Kr, Fg, He (or Ne
A laser gas (9) consisting of s i or hr ) is placed between the opposing first main electrode il+ and the second piezo electrode (21).
(as shown by the arrow in the figure). In this state, the pulse charging is driven by the high voltage power supply (11) w! r
Shino pulse-charges the peaking capacitor (31). At that time, the spare N1 electrode pair (4a) that forms part of the charging path
) and (4b) are connected by a pre-ionization discharge (61). This discharge is an arc discharge, and due to the ultraviolet light (6) emitted from this, the entire area of the discharge excitation part (7) is in a uniform weak ionization state. (the density nθ-10~10).In the charging process of the peaking capacitor (3),
When the voltage between the first main electrode +11 and the second main electrode (2) reaches the discharge starting voltage, the charge stored in the peaking capacitor (31) flows into the main discharge region, and the discharge excitation part 1711r, The main discharge at this time is a uniform pulse discharge because the gas in this region is in a uniform weakly ionized state in advance. KrF in an excited state is formed in the discharge excitation part (7), and the induced Upon emission, laser light is emitted in the direction of the laser oscillation optical axis.

Now, the circuit shown here is called the automatic pre-ionization method,
It is commonly used because its pre-ionization system circuit is extremely simple.

What are the conditions for increasing laser output and efficiency? If you think about it, it is a uniform preliminary type 11i! and uniform excited discharge? Another way to achieve this is to increase the firing voltage of the main discharge and store as much energy as possible in the peaking capacitor before the main discharge starts. The former condition has been achieved to some extent by homogeneous pre-ionization using ultraviolet light. On the other hand, the discharge starting voltage II
It is believed that E is affected by the rate of rise of the voltage applied to the main electrode and the form of pre-ionization, in addition to the generally considered V-de gas type, gas pressure, and main electrode gap length. It became extremely clear. Here, the pre-ionization form refers to the amount of pre-ionization electrons and its change over time until the main discharge is started. K, at which the main discharge is started, uses electrons generated by preliminary ionization as nuclei, and it is necessary to cause electron multiplication by an external electric field to compensate for electrons lost due to electron attachment, recombination, etc. In this discharge initiation process, the amount of pre-ionized electrons and its change over time have a great influence. When pre-ionization is performed at a certain rate at the same time as voltage application starts to the main electrode, electron multiplication occurs from the initial stage 7) 1 according to the voltage rise speed, so the main electrode can be pre-ionized at a relatively low voltage. Discharge begins, making it impossible to achieve high laser output and high efficiency. On the other hand, if pre-ionization is started after a certain period of time has elapsed since the start of voltage application to the main electrode, the pre-ionization (until the JtM ionized electrons are multiplied and a main discharge is formed) Since this requires a certain amount of time, the charging voltage of the peaking capacitor can be increased during that time.It was found that this allows higher output and higher efficiency of the laser to be achieved.

[Problem that the invention seeks to solve]

However, in the conventional automatic pre-ionization method, the pre-ionization discharge is started at the same time as the peaking capacitor is charged, and the pre-ionization electrons are supplied to the discharge excitation section, which lowers the firing voltage of the main discharge and increases the laser output. There was a problem in that it was not possible to achieve high efficiency and efficiency. In addition, the amount of υ pre-ionization is determined by the charging circuit and the peaking capacitor,
Another problem was the lack of controllability regarding optimization of preionization.

This invention was made to solve the above-mentioned problems, and its purpose is to obtain a high-output, highly efficient laser oscillator.

[Means for solving problems]

The laser oscillator according to the present invention has a charging current bypass circuit having a switching function 2 inserted in parallel with a pair of pre-ionizing electrodes inserted in a capacitor charging circuit.

[Effect]

In the present invention, the charging current bypass circuit allows the charging current to flow at the time of starting charging of the peaking capacitor, and stops pre-ionization discharge. After the peaking capacitor has been charged to a certain extent, it acts as if a pre-ionization discharge begins for the first time. That is,
It has the function of delaying pre-ionization discharge.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (13) is a charging current bypass circuit for delaying pre-ionization discharge, and a pre-circuit is inserted in parallel with the pair of mold release poles.

The operation of this invention will be explained below. High voltage power supply (1
The pulse charging circuit (12) driven by 1) fully charges the peaking capacitor (3) in a pulsed manner. At that time, the charging current flows through the charging current bypass circuit θ3),
Preliminary release t(6) is not performed.

When the peaking capacitor (3) reaches a predetermined charging voltage, or (iii) after a certain period of time has passed since the peaking capacitor (3) started fully charging.

A pre-ionization discharge 15) is started, and pre-ionization of the discharge excitation part (7) is started. At this time, the current bypass circuit θ3)
f'i, Preliminary ii*Discharge 16) Acts as a delay circuit for total delay. In this way, when pre-ionization starts during the charging process of the peaking capacitor (31), it takes time to form the main discharge with the pre-charge f11 electrons as the nucleus, so the charging voltage rises during that time and the discharge occurs. The starting voltage increases. When the charging voltage to the peaking capacitor (31) increases, the energy input to the discharge excitation section (7) increases, achieving higher output and efficiency of the laser.

As an example of the current bypass circuit circle in Fig. 2, what is the capacitance of n times (n≧1) the peaking capacitor (3)?
An example is shown in which it is connected to the source bypass capacitor α41'. In this case, at the start of charging, the pulse charging circuit charges a circuit in which the peaking capacitor (3) and the current bypass capacitor α are connected in series. When the charging voltage of the current bypass capacitor 04 reaches the discharge starting voltage of the pre-ionization discharge (6), the pre-ionization discharge +51
is started, and the charging current of the peaking capacitor (3) begins to flow toward the pre-ionization electrode pair (4a) and (4b).

When the pre-ionization discharge (5) is started, a charging voltage equivalent to n times the discharge starting voltage has already been charged across the peaking capacitor +31, and the first main electrode il+ and the first main electrode il+ The discharge starting voltage between the two main electrodes (2) increases according to the delay until the pre-ionization discharge (5) starts, and high output and high efficiency oscillation can be realized. Before the pre-ionization discharge (5) starts, the charge stored in the current bypass capacitor 〇4 is consumed in the pre-ionization discharge [t51, but if ni is increased more than necessary, the charge stored in the current bypass capacitor 〇4 is consumed in the pre-ionization discharge (5). The energy consumed in
On the contrary, it reduces efficiency. Although it depends on the gap length of the pre-ionization electrode pair (5), it is appropriate to set nwl to 0 to 8.0.

In FIG. 8, in a different circuit position from that in FIG. 1,
An example is shown in which the present invention is applied in a case where the pre-ionization electrode pair (4a) and (4b) are inserted. h here
The pulse charging circuit θ is connected to the peaking capacitor (3
), pre-ionization occurs between the pair of pre-ionization electrodes (4a) and (4b) forming part of the charging circuit. (51 is performed in the same way as in the previous case. However, in this circuit, the peaking capacitor +31 discharges charge and in the process of causing an excited discharge, the pre-ionized electrode pair (4a), (4b ) n does not form part of the discharge circuit.In such a circuit configuration, even if the present invention is applied, the same effects as in the above embodiment can be achieved.

Furthermore, in the examples shown in FIGS. 1 and 3, the peaking capacitor (31, charging current bypass circuit 03) is installed inside the laser casing (10), but this does not limit the present invention. Needless to say, the same effect can be achieved even when one or both of them are installed outside the laser housing.

〔Effect of the invention〕

As described above, according to the present invention, a charging current bypass circuit is provided in parallel to a pair of pre-electrodeposition electrodes inserted into a charging circuit of a capacitor for main discharge, and until pre-ionization discharge starts. Since the structure is configured so that a delay is applied to the pulse laser oscillator, a high output and highly efficient pulsed laser oscillator can be obtained.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing a /4 Luz laser oscillator according to an embodiment of the present invention, and FIG. 2 is an embodiment of the pond according to the present invention? FIG. 3 is a vertical cross-sectional view of the vicinity of the radial excitation section shown in FIG.
The figure is a longitudinal cross-sectional view showing a conventional pulsed laser oscillator. In the figure, +t+H first main electrode, (2) is the second main electrode, (31 is the peaking capacitor, (4a), (4b) is the pre-ionization electrode pair, ()) is the discharge excitation part, (9
) is the laser gas, σ is the pulse charging circuit, α3) is the charging current bi) 4 times bB, Q4) is the tri't K bypass capacitor. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (4)

[Claims] (1) A first main electrode and a second main electrode facing each other in the laser gas, a capacitor connected in parallel between the main electrodes, and a pre-ionization electrode pair inserted into the charging circuit of the capacitor. A laser oscillator comprising: a laser oscillator connected in parallel to the pair of pre-ionizing electrodes, bypassing the charging current at least when starting charging of the capacitor, and preventing the discharge occurring between the pair of pre-ionizing electrodes; A laser oscillator characterized by comprising a charging current bypass circuit that delays a period of time. (2) The laser oscillator according to claim 1, wherein the capacitor is charged in a pulsed manner. (3) The laser oscillator according to claim 1 or 2, wherein the charging current bypass circuit is constituted by a current bypass capacitor whose capacity is equal to or larger than that of the capacitor. (4) The laser oscillator according to claim 3, wherein the capacitance ratio of the current bypass capacitor to the capacitor is 1.0 to 3.0.