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

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.

Laser Annealing of Implanted Semiconductor Layers – One Bridge to Nano-Processing

“…One of the first industrial versions of laser annealing equipment was introduced 1987 for annealing of implanted layers in devices in the melt regime with laser pulses of 20 ns duration generated in a solid state laser system [67,68]. By the use of a step-and-repeat method the wafers was mapped with repeated single shot pulses, each illuminating the site of a chip.…”

“…Figure 16 shows the result on a 100 mm-wafer. The problem was solved by combination of scattering plates with kaleidoscopic superposition in the dimension of a chip [68]. Anneal of pn-junctions in FETs and tailoring of crystallite distributions in poly-gates of EEPROMS could be realized [69,70].…”

“…On the first view this basic physical effect cannot be overcome and seems to be the showstopper of laser annealing because the ripple would be reproduced in the pn-junction depth. Scattering-decorrelation-kaleidoscope-systems [34,35] decrease this effect considerably. Superradiance sources like excimer lasers with low coherence also become the tools of choice [36].…”

Recent advances in mixing rods

“…Mixers, especially square and hexagonal cross section mixing rods and hollow tunnels, are often used to achieve this constant output. Applications include Down Lighting, Theater Lighting, Solar [1] [2], Automotive [3], Fiber Optics [4], Lithography [5] [6], Treatment of Skin Lesions [7] [8], Laser Beamshaping [9] [11], and Displays [10]. These same mixers can also be used for other applications that range from kaleidoscopes to Talbot plane coupling to optical computing (e.g., [12][13] [14]).…”