A line narrowing system in which a polarizing beam splitter, a polarization rotator and a reflecting optic are configured to cause light in an expanded beam from a laser gain medium to illuminate a grating at least twice in each pass through the line narrowing system before returning to the gain medium for further amplification. In a preferred embodiment, the grating is an echelle grating arranged in a Littrow configuration.
A line narrowing module includes an elliptical mirror, a diffraction grating disposed at a first focus of the mirror for separating an incident beam into different lines, and a laser beam dispersion and extraction unit. The laser beam dispersion and extraction unit disperses incident laser over the diffraction grating and selectively extract from the resulting lines a laser beam having a desired narrowed bandwidth. A light source that employs the line narrowing module also includes a laser oscillator for generating the beam, and a light returning unit that returns one fraction of the beam extracted from the laser oscillator back to the laser oscillator. Another fraction of the beam is extracted from the laser oscillator through a front window of the laser oscillator, and undergoes line narrowing in the module. The laser beam having the narrowed bandwidth is immediately output as the exposure light from the module.
A laser apparatus and method that provide for suppression of source spontaneous emission (SSE) and amplified spontaneous emission (ASE) light in laser output with minimal intracavity loss. The apparatus comprises a gain medium emitting a light beam, a wavelength element positioned in the light beam, and a non-reciprocal pickoff positioned in the light beam between the gain medium and wavelength element. The non-reciprocal pickoff may comprise a polarization-dependent beam splitter and a non-reciprocal polarization rotator positioned in the light beam before the wavelength selection element. The non-reciprocal pickoff may further comprise a reciprocal polarization rotator positioned in the light beam after the polarization-dependent beam splitter. The method may comprise emitting a light beam from a gain medium outward along an optical path, allowing the outward light beam to interact with a tunable element, returning a spectrally cleaned light beam along the optical path to the gain medium from the tunable element, and non-reciprocally picking off a portion of the returning, spectrally cleaned light beam from the optical path and directing the portion along an output path.
A line-narrowed excimer or molecular fluorine laser system includes a gain medium surrounded by a resonator for generating a laser beam, a discharge circuit including a plurality of electrodes for energizing the gain medium and a line-narrowing unit within the resonator for narrowing the bandwidth of the laser system. The resonator includes a deformable resonator reflector. A technique for adjusting the bandwidth of the laser system includes adjusting a surface contour of the deformable resonator reflector. A desired bandwidth may be selected manually or using a processor which automatically controls the surface contour adjustment.
A first software program for simulating an operating laser system controls a processor that generates one or more dummy parameters each corresponding to a parameter of an operating laser system. The dummy parameter is read over a same or similar signal interface as the operating laser system by a processor running a test software subroutine having the laser system parameter as an input. An algorithm including the test software subroutine then generates an output command based on the value of the dummy parameter. A second software program for efficiently scheduling laser service routines based on a predetermined lithography system schedule controls a processor that reads the lithography system schedule including scheduled system downtimes, wherein the scheduled downtimes include start times and durations. The processor then reads a time window and duration for each of one or more scheduled laser service routines. The processor then determines a start time for each scheduled laser service routine within the time window of the service routine, wherein the start times are selected to collectively maximize temporal overlap of the scheduled laser service routine durations and scheduled system downtime durations. A third software program including a flow control kernel controls a processor to receive a unique command from one of multiple external software control programs corresponding to a function of a laser system and input the unique command to the flow control kernel. The flow control kernel outputs a generic command that is the same for each unique input command of the multiple external software control programs corresponding to the same laser system function. The generic command or command sequence is then input to a generic control module corresponding to the laser system function.
A molecular fluorine (F.sub.2) laser is provided wherein the gas mixture includes molecular fluorine for generating an emission spectrum including two or three closely spaced lines around 157 nm. An optical method and means are provided for selecting an emission line from among the plurality of closely spaced emission lines of the molecular fluorine laser gas volume and broadening the spectrum of said selected emission line. This approach of broadening the spectrum reduces the coherence length of the output beam. As a result, speckle may be reduced or avoided in microlithography applications.
