JP2771028B2 - Pulse laser equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pulse laser device.

[Conventional technology]

FIG. 8 is an excitation circuit diagram of a conventional excimer laser shown in, for example, IEEJ Technical Report (Part II) No. 217 (Present state of short wavelength laser), page 5 (issued in April 1986). In the figure, reference numerals 1 and 2 denote a pair of opposing main discharge electrodes, 3 denotes a peaking capacitor mounted in parallel with the main discharge electrodes 1 and 2, 4 denotes a pulse generating capacitor, and one terminal is connected to the main discharge electrode 1. Have been. Reference numeral 5 denotes a switch connected between the other end of the pulse generating capacitor 4 and the main discharge electrode 2. In this conventional example, a thyratron is used. Reference numeral 6 denotes a charging reactor connected in parallel to the peaking capacitor 3, and reference numeral 7 denotes a charging terminal.

Next, the operation will be described. First, when a positive high voltage is applied to the charging terminal 7, the voltage across the charging current i ₁ is the pulse generating capacitor 4 flow and the peaking capacitor 3 through the charging reactor 6. Figure 9 (a), (b ). The charge voltage V ₁ of the pulse generating capacitor 4 starts to discharge, migration of the charge is performed current i ₂ flows through the peaking capacitor 3.

When t ₀ ≦ t ≦ t ₁ , the pulse generating capacitor 4
When the charge stored in the transitions to the peaking capacitor 3, t = continued discharge between the main discharge electrodes 1 and 2 at t ₁ is started discharge electrode i ₃ flows in the direction of the arrow. In the excimer laser, a preionization discharge is actually performed prior to the main discharge, but electrodes and circuits for this are omitted in FIG. When energy is injected from the peaking capacitor 3 at t ₁ ≦ t ≦ t ₂ , the laser oscillates due to the main discharge generated between the main discharge electrodes 1 and 2. In a laser having a small discharge resistance (for example, 0.2Ω) such as an excimer laser, the voltage V ₂ across the peaking capacitor 3 is ninth.
An oscillating voltage waveform is generated as shown in FIG. 9B, and a voltage of the opposite polarity is generated (FIG. 9B, t = t ₂ ). At the time the vibration is almost completed, at both ends of the pulse generation capacitor 4, voltages of opposite polarity (V _r of Figure 9 (a)) is generated at the time of charging. Flowing the voltage V _r of the opposite polarity becomes the switching current i _4.

FIG. 10 is another pulse laser excitation circuit diagram. In this case, the charge of the pulse generating capacitor 4 is transferred to the charging current i through the saturable reactor 8 acting in a switching manner.
_It flows as ₂₀ and the charge moves to the peaking capacitor 3. This circuit is generally MPC (Magnetic Pulse Compressio
n) A circuit called a circuit, in which another pulse generating capacitor 9 and a current suppressing reactor 10 are added in order to reduce the switching loss in the switch 5. this
Fig. 11 (a) shows the operation waveform of the MPC circuit.
(B), a (c), discharge between the main discharge electrodes 1 and 2 in the conventional example as well as t = t ₁ described in FIG. 8 is started, then, the switching current i ₄ vibrates, final A voltage _Vr having a polarity opposite to that of the initial state is generated at both ends of the pulse generating capacitor 4.

[Problems to be solved by the invention]

Since the conventional pulse laser apparatus is constructed as described above, the reverse voltage V _r of opposite polarity is generated across the pulse generation capacitor after the main discharge electrodes flows. The energy of the reverse voltage (= (1/2) CV _r ² ) is consumed as an arc or a streamer between the main discharge electrodes considerably after the main discharge occurs (for example, after about 1 μs). This is a so-called after current, which does not contribute to laser oscillation, and has a problem that the main discharge electrode is damaged and the electrode life is shortened. In addition, there is a problem that high repetition oscillation cannot be performed when an after current flows.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a pulse laser device capable of preventing damage to electrodes, extending the life thereof, and performing high repetition oscillation.

[Means for solving the problem]

The pulse laser device according to the first aspect of the present invention includes a pulse generating capacitor in which one terminal is connected to one electrode of a main discharge electrode that generates a laser by main discharge, and the other terminal is connected to a charging terminal. A peaking capacitor connected in parallel to the main discharge electrode and performing a main discharge of the laser output in response to the transfer of the charge of the pulse generating capacitor; a switch connected between the charging terminal and the other electrode of the main discharge electrode; An inversion current avoidance circuit connected in parallel with the generation capacitor and configured by a series connection of a current control element and a resistor to avoid an inversion current due to an inverse voltage applied to the main discharge electrode after the main discharge, and a pulse generation capacitor and an inversion To include a supersaturated reactor connected in series with a circuit formed by connecting a current avoidance circuit in parallel, and a charging resistor connected in parallel with the main discharge electrode. Are those that form.

A pulse laser device according to a second aspect of the present invention includes a pulse generating capacitor in which one terminal is connected to one electrode of a main discharge electrode that generates a laser by main discharge, and the other terminal is connected to a charging terminal. A peaking capacitor connected in parallel to the main discharge electrode and performing a main discharge of the laser output upon receiving the transfer of the charge of the pulse generation capacitor, and a switch connected between the charging terminal and the other electrode of the main discharge electrode; A reversal current avoidance circuit that is connected in series with a pulse generating capacitor and is configured by a parallel connection of a resistor and a series body of a current control element and a saturable reactor to avoid a reversal current due to a reverse voltage applied to a main discharge electrode after a main discharge. And a charging resistor connected in parallel with the main discharge electrode.

[Action]

The inversion current avoiding circuit according to the present invention is connected to a key point of a circuit capable of reducing a reverse voltage in order to avoid an inversion current caused by a reverse voltage applied to a main discharge electrode after a main discharge. To prevent or generate a reverse voltage between the main discharge electrodes.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same parts as those in FIGS. 8 to 10 are denoted by the same reference numerals. In FIG. 1, 11 is a diode (current control element), 12 is a resistor, and the series body of the diode 11 and the resistor 12 is It is connected in parallel with the pulse generating capacitor 4. The diode 11 is connected so that it is in a non-conductive state with respect to the charging polarity from the charging terminal 7. Reference numeral 13 denotes a switch including a pulse generating capacitor 4 and a thyratron. In this case, in parallel with the main discharge electrodes 1 and 2, a pulse generating capacitor 4, a switch 5 composed of a thyratron, and a switch composed of a saturable reactor
Thirteen series bodies are connected.

Here, a circuit formed by the diode 11 and the resistor 12 is referred to as a reversal current avoidance circuit.

Next, the operation will be described. First, when the charging current i ₁ flows through the pulse generating capacitor 4 to perform charging, t =
At t ₀ , a trigger is applied to the switch 5 composed of a thyratron, and the electric charge previously charged in the pulse generating capacitor 4 is discharged as a current i ₂ . The time after the time determined by the voltage × time product of the switch 13 by the saturable reactor (second view of t = t _01), the charge is transferred from the pulse generating capacitor 4 to the peaking capacitor 3. The voltage waveform is shown in FIG. Next, at t = t _1, the main discharge electrodes 1 and 2
Main discharge starts between them, and a current i ₃ flows, and at t = t ₂ , the voltage of the peaking capacitor 3 is inverted. t = t ₂ after,
A reverse voltage is going to be generated in the pulse generating capacitor 4, but a diode 11 is connected in parallel to the pulse generating capacitor 4.
And the reverse current avoidance circuit of the resistor 12 is connected, the bypass current i ₄ flows, and no reverse voltage is generated in the pulse generating capacitor 4. Therefore, extra energy generated as a result of the vibration after the main discharge is consumed by the resistor 12. As a result,
There is no after current (reversal current) flowing between the main discharge electrodes 1 and 2, and no arc or streamer is generated. In this embodiment, by connecting the switch 13 made of a supersaturated reactor, there is an advantage that the response speed required for the diode 11 may be slightly lower. This is for the following reason.

The switch 13 composed of a supersaturated rear criter in FIG.
Since saturation occurs in the direction of the solid arrow shown in the drawing, once reverse charges accumulate in the pulse generating capacitor 4, the switch 13 formed of the supersaturated reactor enters a blocking state to stop the oscillation of the charges thereafter. The diode 11 only has to allow the reverse charge to flow slowly through the resistor 11 within a relatively long time (for example, 200 ns) while the switch 13 composed of the saturable reactor blocks the voltage. Therefore, the response speed of the diode 11 may be slow, and the peak current can be reduced. Therefore, an inexpensive diode regardless of the response speed can be used.

Further, unlike FIG. 1, an embodiment in which a high-speed, large-current diode (current control element) 11A is used is shown in FIG. In this case, even if a switch composed of a supersaturated reactor is not used, the response characteristic of the diode is fast, so that the same effect as that of the above embodiment can be obtained.

FIG. 4 is a diagram for avoiding the reversal current in the conventional example shown in FIG. 10. In FIG. 4, a switch 8 composed of a saturable reactor and a capacitor 4 for pulse generation are connected in parallel between the main discharge electrodes 1 and 2. A series body is connected, and a series body (inversion current avoidance circuit) of a diode and a resistor 12 is connected in parallel with the pulse generating capacitor 4. First, the charge that has been charged by the charging current i ₁ flowing through the pulse generating capacitor 9 is transferred to the pulse generating capacitor 4 by the switch 5 composed of a thyratron (current i ₂ ).
Since the diode 11 is connected in the non-conductive state with respect to the polarity of the current in which the pulse generating capacitor 4 is charged first, the charge of the inverted current charged in the peaking capacitor 3 is switched by the supersaturated reactor. 8
Is released, the discharge current i ₄ is generated at a stroke and the diode 11 is bypassed. Therefore, also in this case, the same effect as that of the above embodiment is obtained.

In the above embodiment, when the peaking capacitor 3 is used (for example, the embodiment shown in FIG. 5), the same effects as those of the above embodiment can be obtained. In this case, if the diode 11A is a high-speed, large-capacity diode, the effect is still greater.

FIG. 6 shows another embodiment of the present invention. Here, a peaking capacitor 3 and a pulse generating capacitor 4
A diode 11 is disposed in series with a circuit including the switch 5 and a resistor 12 is connected in parallel with the diode 11.

In this case, the pulse generating capacitor 4 is connected to the charging terminal 7.
The charging current i ₁ is supplied through the resistor 12 and the inductance 6. When the switch 5 is turned on, the electric charge stored in the pulse generating capacitor 4 is transferred to the diode 1
1. The current is transferred (current i ₂ ) to the peaking capacitor 3 arranged in parallel with the discharge unit through the switch 5. Moves to involve voltage between main discharge electrodes 1 and 2 is increased, eventually the main discharge (the current flows i ₃₎ the laser starts to generate.

By the way, a part of the electric charge stored in the capacitors 3 and 4 is not consumed by the discharging unit and tends to oscillate between the capacitors 3 and 4. Since the direction of the current at this time is a reverse voltage to that when the laser is generated, while blocking with the diode 11,
If the value of the resistor 12 is made sufficiently large, it is consumed here, and as a result, the oscillation (reversal) current value is suppressed.

In this case, since the diode 11 is required to have high speed,
Many high-speed diodes are used in series and parallel, but supersaturated reactor (MPC) (current control inhibition) (11 (a) in the figure)
May be used. In this case, the saturation effect is lost when saturation occurs. However, the saturation time may be adjusted so that the discharge disappears within that time. If the saturable reactor is combined with a low-speed diode (current control blocking) (11 (b) in the figure), the effect of the voltage block of the saturable reactor and the synergistic effect due to the decrease in the resistance of the large current diode when the block is opened are obtained. Even better effects can be obtained.

In the embodiment, the charging circuit has an inductance of 6%.
However, since the energy stored in the inductance may become an arc when discharged, it is better to use the resistor 6A rather than the inductance.

FIG. 7 shows another embodiment of the present invention. In this case, the diode 11 of the reversal current avoidance circuit (for vibration suppression) is inserted in the circuit composed of the peaking capacitor 3 and the main discharge electrodes 1 and 2. When the vibration is suppressed by the diode 11, the energy remaining in the peaking capacitor 3 is
Consumed by 6A.

In the above embodiment, an example using a diode or a saturable reactor has been described. However, a current control element having a function of controlling current, for example, a diode or a thyristor,
A varistor or the like may be used. The resistor 12 may be replaced by an internal resistor such as a diode. However, in order to surely consume the energy of the reverse voltage and prevent the generation of the reversal current, the resistor 12 is preferably provided.

In the above embodiment, an example in which a thyratron is used as the switch 5 has been described. However, a series switch of a semiconductor switch (thyristor, SIT transistor, FET, IGBT, or the like) may be used, or a switch such as a spark gap or a rail switch may be used. good. In addition, although the charging is performed from the charging terminal 7 with a positive polarity, the charging may be performed with a negative polarity. In any case, the same effects as in the above embodiment can be obtained.

In the above embodiment, an excimer laser was described as a laser. However, any laser can be used as long as it has a small discharge resistance and vibrates the discharge current. Play.

It should be noted that the same effect as in the above embodiment can be obtained by using a pulse shaping circuit which is a distributed constant circuit instead of the capacitor of the above embodiment.

Further, even greater effects can be expected by combining the above embodiments.

〔The invention's effect〕

As described above, according to the present invention, a pulse generating capacitor in which one terminal is connected to one electrode of a main discharge electrode that generates a laser by main discharge, and the other terminal is connected to a charging terminal, A peaking capacitor that is connected in parallel to the pulse generation capacitor to perform main discharge of the laser output in response to the transfer of the charge of the pulse generation capacitor, a switch connected between the charging terminal and the other of the main discharge electrodes, Connected by a direct connection between the current control element and the resistor, or a parallel connection of the resistor and the series body of the current control element and the saturable reactor. A reverse current avoidance circuit is provided to avoid the transition current and the main discharge current. Arcing and streamers in the machining gap is alleviated the effect can be eliminated damage of the main discharge electrodes. Also, since high repetition oscillation is possible,
There is an effect that highly efficient operation of the laser can be realized.

Further, since the supersaturated reactor is provided, a current control element having a slow response speed can be used, and an inexpensive current control element can be used.

Further, since the charging circuit is configured using the charging resistor instead of the charging reactor, there is also an effect that generation of an oscillating current due to the charging reactor can be suppressed.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a pulse laser device according to one embodiment of the present invention, FIG. 2 is a voltage waveform diagram showing the operation of FIG. 1,
3 to 7 are circuit diagrams of a pulse laser device showing another embodiment of the present invention, FIG. 8 is a circuit diagram of a conventional pulse laser device, and FIG. 9 is an operation of FIG. FIG. 10 is a voltage waveform diagram, FIG. 10 is a circuit configuration diagram of another conventional pulse laser device, and FIG. 11 is a voltage waveform diagram showing the operation of FIG. In the figure, 1, 2 is the main discharge electrode, 3 is the peaking capacitor, 4, 9 is the pulse generation capacitor, 5 is the switch,
7 is a charging terminal, 11 is a diode (current control element, reverse current avoidance circuit), 11A is a large current diode (current control element, reverse current avoidance circuit), 11a is a saturable reactor (current control element, reverse current avoidance circuit), 11b is a low-speed diode (current control element, supersaturation reactor), and 12 is a resistor (inversion current avoidance circuit). In the drawings, the same reference numerals indicate the same or corresponding parts.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Haruhiko Nagai 8-1-1 Tsukaguchi Honcho, Amagasaki-shi, Hyogo Mitsubishi Electric Corporation Central Research Laboratory (56) References JP-A-62-152189 (JP, A) JP-A-62-244183 (JP, A) JP-A-63-318096 (JP, A) JP-A-63-299288 (JP, A) JP-A-64-66985 (JP, A) JP-A-4-39977 (JP JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01S 3/097-3/0977 H01S 3/03-3/038

Claims (2)

(57) [Claims] 1. A pulse generating capacitor having one terminal connected to one electrode of a main discharge electrode for generating a laser by main discharge and the other terminal connected to a charging terminal, and connected in parallel to the main discharge electrode. A peaking capacitor for performing a main discharge of the laser output in response to the transfer of the charge of the pulse generating capacitor, a switch connected between the charging terminal and the other of the main discharge electrodes, An inversion current avoidance circuit connected in parallel with a capacitor and configured by a series connection of a current control element and a resistor, for avoiding an inversion current due to an inverse voltage applied to the main discharge electrode after main discharge; and A supersaturated reactor connected in series with a circuit formed by connecting inversion current avoidance circuits in parallel, and a charging resistor connected in parallel with the main discharge electrode are provided. Pulse laser apparatus. 2. A pulse generating capacitor having one terminal connected to one electrode of a main discharge electrode for generating a laser by a main discharge and the other terminal connected to a charging terminal, and connected in parallel to the main discharge electrode. A peaking capacitor for performing a main discharge of the laser output in response to the transfer of the charge of the pulse generating capacitor, a switch connected between the charging terminal and the other of the main discharge electrodes, An inversion current avoidance circuit connected in series with a capacitor, configured by a parallel connection of a resistor and a series body of a current control element and a saturable reactor, and avoiding an inversion current due to an inverse voltage applied to the main discharge electrode after main discharge, A pulse laser device comprising: the main discharge electrode; and a charging resistor connected in parallel.