Precise monitor etalon calibration technique
AssigneeLambda Physik AG
InventorsHans-Stephan Albrecht, Uwe Stamm, Wolfgang Zschocke
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Abstract
A method for operating an excimer or molecular fluorine laser system at a stabilized wavelength includes generating a laser beam and directing a beam portion through a wavelength measurement system, calibrating the wavelength measurement system to an absolute reference, determining the wavelength of the laser beam including figuring in a drift compensation value of the wavelength, and tuning the wavelength to a target wavelength when the determined wavelength differs from the target wavelength.
Claims19
A method for compensating optical drift of a wavelength measurement system used for relative wavelength tuning of an output beam of an excimer or molecular fluorine laser system, comprising the steps of:
- (a) operating the laser system including generating a laser beam and directing a beam portion through the wavelength measurement system;
- (b) calibrating the wavelength measurement system to an absolute reference;
- (c) tuning the output beam to a target wavelength using the wavelength measurement system;
- (d) detecting a measured wavelength of the output beam using the wavelength measurement system after a predetermined period of laser operation;
- (e) calculating a compensated wavelength by figuring in a previously determined measurement system drift compensation value;
- and
- (f) adjusting the wavelength of the laser beam to the target wavelength when the compensated wavelength differs from the target wavelength.
A method for operating an excimer or molecular fluorine laser system at a stabilized wavelength, the laser system including a wavelength measurement system calibrated to an absolute reference, for relative wavelength tuning, comprising the steps of:
- (a) operating the laser system including generating a laser beam and directing a beam portion through the wavelength measurement system;
- (b) calibrating the wavelength measurement system to an absolute reference;
- (c) determining the wavelength of the laser beam, said wavelength determining step comprising the steps of:
- (i) transmitting wavelength information measured by said wavelength measurement system;
- (ii) retrieving a drift compensation value for the measurement system stored as corresponding to a current laser system operating condition;
- and
- (iii) calculating the wavelength of the laser beam based on the transmitted wavelength information and the retrieved drift compensation value for the measurement system;
- and
- (d) tuning the wavelength to a target wavelength when the determined wavelength differs from the target wavelength.
A method for preparing an excimer or molecular fluorine laser system to operate at a stabilized wavelength by compensating optical drift of a wavelength measurement system used for relative wavelength tuning of an output beam of the excimer or molecular fluorine laser system, comprising the steps of:
- (a) operating the laser system including generating a laser beam and directing a beam portion through the wavelength measurement system;
- (b) calibrating the wavelength measurement system to an absolute reference;
- (c) determining a value of the wavelength of the laser beam measured by the wavelength measurement system after a predetermined period of laser operation;
- (d) comparing the value of the wavelength measured by the wavelength measurement system after said predetermined period of laser operation with an actual value of the wavelength of the laser beam;
- and
- (e) determining a drift compensation value for the measurement system based on a result of the comparing step.
A method for preparing an excimer or molecular fluorine laser system to operate at a stabilized wavelength by compensating optical drift of a wavelength measurement system used for relative wavelength tuning of an output beam of the excimer or molecular fluorine laser system, comprising the steps of:
- (a) operating the laser system including generating a laser beam at a target wavelength by orienting a tuning optic of the laser system at a first position and directing a beam portion through the wavelength measurement system;
- (b) calibrating the wavelength measurement system to an absolute reference;
- (c) orienting said tuning optic to a second position such that the wavelength of the laser beam measured by the wavelength measurement system after a predetermined period of laser operation is at the target value;
- (d) comparing the first position with the second position of the tuning optic;
- and
- (e) determining a drift compensation value for the measurement system based on a result of the comparing step.
Dependencies are inferred from the claim text.