Emission timing control apparatus for pulsed laser

• US 6,400,741 B1
• Filed: 03/31/1999
• Issued: 06/04/2002
• Est. Priority Date: 04/01/1998
• Status: Expired due to Term

• Current Assignee: Gigaphoton, Inc. (Komatsu Ltd.)
• Original Assignee: Komatsu Ltd.
• Inventors: Matsui, Akinori, Matsunaga, Takashi
• Primary Examiner(s): Leung, Quyen
• Assistant Examiner(s): MENEFEE, JAMES A
• Application Number:
  US09/282,222
• Time in Patent Office: 1,161 Days
• Field of Search: 372/38.02, 372/38.03, 372/38.04, 372/38.1, 372/38.07, 372/37, 372/86, 372/25, 372/38.01, 372/38.08, 372/29.01, 372/29.011, 372/29.012, 372/29.013, 372/29.014, 372/29.015, 372/29.016, 307/106
• US Class Current: 372/38.02
• CPC Class Codes: H01S 5/042 Electrical excitation ; Circuits therefor monolithically integrated laser drive components H01S5/0261
• CPC Class Codes: H01S 5/0428 for applying pulses to the laser

Abstract

An emission timing control apparatus for a pulsed laser including a magnetic pulse compression circuit having a switching section for carrying out a switching operation to connect and disconnect a charging power source to and from the magnetic pulse compression circuit. The pulsed laser executes pulsed laser oscillation at a prescribed repetition frequency by turning on the switching section with a pulse oscillation synchronizing signal having the prescribed repetition frequency received from a semiconductor exposure apparatus, in which the emission timing control apparatus includes a reference delay time setting section for setting a prescribed reference delay time, and delay section for delaying a pulse oscillation synchronizing signal received from the semiconductor exposure apparatus by the time difference τ calculated in the delay time calculating section and outputting to the switching section.

Claims

1. An emission timing control apparatus for a pulsed laser comprising:

a magnetic pulse compression circuit including a multi-stage charge transfer circuit comprised of a plurality of magnetic switches connected serially to a charging power source and a plurality of capacitors connected parallel to the charging power source, for compressing current pulses in a plurality of stages using the multi-stage charge transfer circuit;

switching means for carrying out a switching operation to connect and disconnect the charging power source to and from the magnetic pulse compression circuit;

a laser discharge electrode connected to an output terminal of the magnetic pulse compression circuit;

control means for outputting a voltage command value to the charging power source,

wherein the laser executing pulsed laser oscillation at a predetermined repetition frequency by turning on the switching means via a pulse oscillation synchronizing signal having the predetermined repetition frequency received from a semiconductor exposure apparatus;

reference delay time setting means for setting a predetermined reference delay time, the predetermined reference delay time being greater than a maximum value of a variable range of a real emission delay time from when the switching means is turned on until laser oscillation begins;

delay time calculating means for calculating for each pulse oscillation a difference between the predetermined reference delay time for a pulse oscillation corresponding to the voltage command value output from the control means; and

delay means for delaying the pulse synchronizing oscillation signal received from the semiconductor exposure apparatus by the time difference calculated in the delay time calculating means and outputting a delayed signal to the switching means.

2. The emission timing control apparatus for a pulsed laser according to claim 1, wherein the delay time calculating means finds a real emission delay time of the pulse oscillation according to an ambient temperature of the magnetic pulse compression circuit and the voltage command value output from the control means, and outputs a difference between the preset reference delay time and the real emission delay time of the pulse oscillation to the delaying means.

3. The emission timing control apparatus for a pulsed laser according to claim 2, wherein the voltage command value output from the control means is variably controlled between a predetermined lower limit value and a predetermined upper limit value;

and

the predetermined reference delay time set in the reference delay time setting means is set as a time from when the switching means is turned on until laser oscillation begins, when the laser oscillation is effected at a predetermined voltage value below the lower limit value below the lower limit value of the voltage command value.

4. The emission timing control apparatus for a pulsed laser according to claim 3, wherein the upper limit value of the voltage command value is established so that a charge transfer time among the capacitors matches a saturation time of the magnetic switch.

5. The emission timing control apparatus for a pulsed laser according to claim 1, wherein the voltage command value output from the control means is variably controlled between a predetermined lower limit value and a predetermined upper limit value;

and

the predetermined reference delay time set in the reference delay time setting means is set as a time from when the switching means is turned on until laser oscillation begins, when the laser oscillation is effected at a predetermined voltage value below the lower limit value of the voltage command value.

6. The emission timing control apparatus for a pulsed laser according to claim 5, wherein the upper limit value of the voltage command value is established so that a charge transfer time among the capacitors matches a saturation time of the magnetic switch.

7. The emission timing control apparatus for a pulsed laser according to claim 1, wherein the delay time calculating means finds the real emission delay time of the pertinent pulse oscillation corresponding to the voltage command value output from the control means by approximation calculation, with the below hyperbolic approximation equation:

8. An emission timing control apparatus for a pulsed laser comprising:

a magnetic pulse compression circuit;

a charging power source;

switching means for carrying out a switching operation to connect and disconnect the charging power source to and from the magnetic pulse compression circuit;

a laser discharge electrode connected to an output terminal of the magnetic pulse compression circuit;

control means for outputting a voltage command value to the charging power source;

reference delay time setting means for setting a predetermined reference delay time, the predetermined reference delay time being greater than a maximum value of a variable range of a real emission delay time from when the switching means is turned on until laser oscillation begins;

delay time calculating means for calculating for each pulse oscillation a difference between the predetermined reference delay time for a pulse oscillation corresponding to the voltage command value output from the control means; and

delay means for delaying a pulse oscillation synchronizing signal received from a semiconductor exposure apparatus by the time difference calculated in the delay time calculating means and outputting a delayed signal to the switching means.