Polycrystalline Si films with unique microstructures formed from amorphous Si films by non‐thermal equilibrium flash lamp annealing

Abstract

AbstractFlash lamp annealing (FLA), with millisecond‐order duration, can crystallize amorphous silicon (a‐Si) films a few μm thick on glass substrates, resulting in formation of polycrystalline Si (poly‐Si) films with unprecedented periodic microstructures. The characteristic microstructure, formed spontaneously during crystallization, consists of large‐grain regions, containing relatively large grains more than 100 nm in size, and fine‐grain regions, including only 10‐nm‐sized fine grains. The microstructures results from explosive crystallization (EC), driven by heat generation corresponding to the difference of the enthalpies of meta‐stable a‐Si and stable crystalline Si (c‐Si) states, which realizes lateral crystallization velocity on the order of m/s. The lateral crystallization may stop when the temperature of a‐Si in the vicinity of c‐Si, which is decided by both homogeneous heating from flash irradiation and thermal diffusion from c‐Si, falls below a crystallization temperature. This idea is supported by the experimental fact that a lateral crystallization length decreases with decreasing pulse duration. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)