Optical pulse stretching and smoothing for ArF and F2 lithography excimer lasers
AssigneeLambda Physik AG
InventorsKlaus Mann, Thomas Schröder, Bernd Schäfer, Uwe Leinhos, Uwe Stamm
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Abstract
A method and apparatus are provided for temporally stretching and smoothing of the pulses of an output beam of excimer and lithography lasers. The method and apparatus are based upon providing an optical delay line or circuit having a plurality of optical reflectors and a plurality of beam recombiners or splitters so arranged as to divide the pulse into numerous portions which vary in their travel time through the circuit. As a result, the energy of the incident pulse is greatly stretched and smoothed.
Claims39
An optical pulse stretcher, comprising a plurality of optical beam splitters for dividing a laser pulse into multiple beam portions including multiple delayed beam portions, a plurality of optical reflectors configured with said optical beam spliters so as to provide an optical delay circuit characterized by a plurality of reflections and a plurality of different optical path lengths for said delayed beam portions to travel;
- and wherein said beam splitters and optical reflectors direct said beam portions into, around, or out of, said circuit, and wherein said laser pulse is stretched and thereby a peak intensity of said laser pulse is reduced such as to substantially reduce damage to optical materials in the beam path after the pulse stretcher.
An optical pulse stretcher, comprising:
- a) a first beam splitter located in the path of said pulse for transmitting a first portion of an output pulse and reflecting a second portion of said pulse;
- b) a plurality of optical reflectors positioned to redirect said second portion along a route which intersects said first portion and thereafter intersects said first beam splitter;
- and
- c) a second beam splitter located at the point where said route intersects with said path of said first portion;
- wherein said second beam splitter is oriented to reflect a portion of said second portion in a manner to recombine said reflected second portion with a portion of said first portion which is transmitted by said second beam splitter, said second beam splitter also functioning to transmit a portion of said second portion and reflect a portion of said first portion in a manner to recombine said transmitted portion of said second portion and said reflected portion of said first portion, and
- wherein said output pulse is stretched and thereby its peak intensity is reduced such as to substantially reduce damage to optical materials in the beam path after the pulse stretcher.
An optical pulse stretcher, comprising:
- a) a first beam splitter located in the path of said pulse for transmitting a first portion of an output pulse and reflecting a second portion of said pulse;
- b) a second beam splitter located in the path of said pulse for transmitting a portion of said pulse and reflecting a third portion of said pulse;
- c) a plurality of prisms positioned to delay said second portion and said third portion different amounts by passage along a cascaded route which increases the amount of said delay for a given prism spacing;
- and
- d) a means of recombining said second portion and said third portion with said first portion, and
- wherein said output pulse is stretched and thereby its peak intensity is reduced such as to substantially reduce damage to optical materials in the beam path after the pulse stretcher.
Dependencies are inferred from the claim text.