Interference laser crystallization of microcrystalline silicon using asymmetric beam intensities

Periodic interference patterns formed by two laser beams of different intensities are used to crystallize films of amorphous (a-Si) and crystalline silicon with nanometer sized crystallites (nc-Si). This asymmetric interference is applied to generate variable temperature profiles to optimize super lateral growth (SLG). The structural properties of the laser crystallized silicon layers have been determined by Secco etching and atomic force microscopy. The results show that, independently of the applied intensity pattern, 1.3-1.5 μn long and ca 0.4 μm wide grains can be grown by SLG. This growth lasts for about 100 ns, it is limited by spontaneous nucleation in the center of the liquid and is independent of the applied intensity profile. The use of a-Si or nc-Si as initial material makes no detectable difference despite the fact that the total laser intensity has to be larger for nc-Si.