AXIALLY CONTROLLED SOLID-PHASE CRYSTALLIZATION OF AMORPHOUS-SILICON

The crystallization behavior of a-Si films has been investigated as a function of the annealing temperature T(a) (530-1100-degrees-C) and time (0-72 h) by means of X-ray diffraction, transmission electron microscopy (TEM) and Raman scattering. The a-Si films were deposited by low-pressure chemical vapor deposition (LPCVD) onto poly-Si films with a strong <110> texture prepared by plasma-enhanced CVD (PECVD) [poly-Si(P)], and onto fused quartz substrates [poly-Si(Q)]. Poly-Si(P) films were crystallized maintaining the same strong <110> texture as the PECVD poly-Si substrate, over the entire T(a) range. However, poly-Si(Q) films exhibited a weak <111> texture. The final grain size estimated by TEM for poly-Si(P) films was independent of T(a), but became 7-8 times larger than that for the poly-Si substrate. The crystallization mechanism of poly-Si(P) films was discussed in comparison with that of poly-Si(Q) films.