Microstructural characterization of polycrystalline Si films grown by vapor-induced crystallization of amorphous Si using Al/Ni chloride

Abstract

A polycrystalline Si film with uniform and large grains can be grown by crystallizing with Al/Ni chloride vapor transport. At the initial stage of crystallization, the poly-Si grains had round-shaped cores with needles at the growth front. It showed that the needles were grown by the Ni-induced lateral crystallization process and the sidewall of the needles was enlarged by the Al-induced crystallization process. The needles were emerged coherently to an extent by the sidewall growth. As a result, a poly-Si film with grains larger than 15 mu m diam and fewer intragrain defects was obtained. The Ni concentration was constant through out the film thickness with a value of 1 x 10(19) cm(-3). The Al concentration at the surface was 10(19) cm(-3) and was reduced below 10(16) cm(-3) at 25 -nm depth. The thin film transistor utilizing the film showed an electron mobility of 47 cm(2)/V s at a drain voltage of V-d = 0.1. But the threshold voltage was 5.2 V that is considered as relatively high due to Al doping. (c) 2007 The Electrochemical Society.