| 摘要 |
An excimer laser with optical pulse multiplication. A pulse multiplier optical system receives the laser output beam and produces a multiplier output beam having a larger number of pulses, each with substantially reduced intensity values as compared to the laser output beam. The present invention is particularly important as an improvement to the ArF excimer laser to reduce two-photon absorption damage to optical equipment in lithography machines. For damage mechanisms involving two-photon processes, such as the compaction and solarization of fused silica in the DUV spectral region, a factor of 4 reduction in peak power decreases the quantity of two photon absorption damage done by the synthesized 4-pulse burst by a factor of about 16 compared to delivering all of the energy in the single pulse emitted by the laser. This is a useful method of prolonging the lifetime of very expensive beam delivery systems such as those used in photolithography stepper systems without reducing the total dose available at the wafer. In preferred embodiments, the pulse multiplier system is contained in a module which can be pre-aligned and quickly installed on the excimer laser.
|
