Effect of process parameters on the structural characteristics of laterally grown, laser-annealed polycrystalline silicon films

Abstract

In this work, we have conducted a systematic study aiming at assessing the effects of process parameters on the microstructural characteristics of laterally grown polycrystalline silicon (poly-Si) films. Poly-Si films were formed by the sequential lateral solidification (SLS) method. The Si film thickness was found to affect significantly the quality of the poly-Si microstructure, manifested by a decreased crystal-growth defect density and increased subboundary spacing in thicker films. A weak (100) texture was observed in the lateral growth direction, except for very thin films (<30 nm) where (110) texture was observed. No specific texture was identified in the normal and transverse directions. Lateral crystallization proceeds by seeded, lateral epitaxial growth at an advancing pitch. We investigated the quality of lateral growth as a function of the advancing, substrate pitch. We found that an optimum pitch range exists, bound on the low end by the detailed shape of the beam-edge profile and on the high end by the quality of crystal formed under deep, interfacial undercooling. In that sense, only a fraction of the laser beamlet can be effectively used for lateral growth and the process should be tuned towards maximizing this fraction. Thin film transistor data were used to further refine the considerations driving the selection of optimum process parameters for SLS lateral crystallization providing the least sensitivity to process-induced variations.