NICKEL INDUCED CRYSTALLIZATION OF AMORPHOUS-SILICON THIN-FILMS

Nickel (Ni) induced crystallization of amorphous silicon (a-Si) has be en studied by selective deposition of Ni on a-Si thin films. The a-Si under and near the Ni-covered regions was found to be crystallized aft er heat treatment at 500 degrees C from 1 to 90 h. Micro-Auger electro n spectroscopy revealed that a large amount of Ni stayed in the region under the original Ni coverage, but no Ni was detected either in the crystallized region next to the Ni coverage or in the amorphous region beyond the front of the laterally crystallized Si. X-ray photoelectro n spectroscopy revealed a nonuniform Ni distribution through the depth of the crystallized film under the original Ni coverage. In particula r, a Ni concentration peak was found to exist at the interface of the crystallized Si and the buried oxide. It was found that a layer of 5-n m-thick Ni could effectively induce lateral crystallization of over 10 0 mu m of a-Si, but the lateral crystallization rate was found to decr ease upon extended heat treatment. Transmission electron microscopy an alysis showed that the crystallized film under the Ni coverage was com posed of randomly oriented fine grains, while that outside the Ni cove rage was mainly composed of large (110)-oriented grains. A unified mec hanism is proposed to explain the Ni induced crystallization of a-Si a nd possible reasons for the reduction in the lateral crystallization r ate are discussed. (C) 1998 American Institute of Physics.