High-performance laser beam shaping and homogenization system for semiconductor processing

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Abstract
The laser beam shaping system described is used for high-power pulse lasers of high spatial and moderate temporal coherence. It provides an exact flat-top intensity profile with a maximum of a 1*1 cm2 rectangular cross section, by means of a two-step splitting of the beam into mutually incoherent parts and by superimposing decorrelated speckle patterns in a diffusing/light-guiding system. After clipping the edges of the intensity distribution, the profile is projected onto the target by means of a double-telecentric optical system. Using the radiation of a Q-switched Nd-glass laser, a flatness of the macroscopic intensity profile with maximum +or-1% deviation from the mean intensity and a nearly speckle-free microscopic intensity distribution could be achieved that exhibited a contrast ratio of less than 0.03 at 2-3 mu m lateral dimension of the residual inhomogeneities.