Large-Grain Polycrystalline Silicon Films Formed through Flash-Lamp-Induced Explosive Crystallization

Abstract

The flash lamp annealing (FLA) of electron-beam- (EB-) evaporated amorphous silicon (a-Si) films results in the formation of polycrystalline Si (poly-Si) films with at least a few µm long grains stretching along lateral crystallization directions. Unlike the case of using chemical-vapor-deposited (CVD) hydrogenated a-Si films as precursors, no peeling of Si films occurs even in the absence of Cr adhesion layers. Such a flash-lamp-induced crystallization occurs also in doped EB-evaporated a-Si films as in the case of undoped films. The p+/p-/n+ stacked structure is sufficiently kept even after crystallization, although the profiles of dopants are slightly modified. This fact clearly indicates that the crystallization observed is not based on liquid-phase epitaxy (LPE) after the complete melting of the whole a-Si precursor during millisecond-order treatment but through LPE-based explosive crystallization (EC), self-catalytic lateral crystallization driven by the release of latent heat. The formation of poly-Si films with large grains and the sufficient preservation of dopant profiles would lead to the utilization of the poly-Si films formed for solar cell devices.