Growth of polycrystalline silicon at low temperature on hydrogenated macrocrystalline silicon(μ c-Si:H) seed layer

Abstract

ABSTRACTHigh quality polycrystalline silicon (poly-Si) films were deposited on SiO2 substrate using hydrogenated microcrystalline silicon (μ c-Si:H) seed layer by very high frequency (182.5MHz) sputtering system and Chemical Vapor Deposition (CVD) system in pure Ar ambient at atemperature of 300°C. In this study, we investigated the correlation between the initial seed layer conditions and the grown layer, and studied the nucleation process. Electrical characteristics and surface roughness of the grown layer as a function of film thickness and deposition rate will be shown. Grown layers were deposited on several kinds of hydrogenated seed layers in pure Ar ambient. The resistivity and Hall mobility of the grown layer are 0.33Ω.cm and 7.5cm2/V-sec respectively for a film with thickness of 3000Å. In this measurement, we found that the resistivity is lower as deposition rate is slower, and when deposition rate is relatively high, the resistivity increases with thickness. On the contrary, in the case of low deposition rate, resistivity decreases as film thickness increases. For the deposition rate of 0.32Å/sec, the surface roughness ranges over 1.39Å-8.52Å. This is a very smooth surface compared to hydrogenated polycrystalline silicon films. The resistivity of grown layer dramatically decreases in proportion to that of the seed layer. From Reflection High Energy Electron Diffraction (RHEED) patterns, it is clearly shown that the film is crystallization of occurred in the earlier stage than that of conventional deposited film. Our results shows that the electrical characteristics of the films are affected by the conditions of the seed layer and the deposition rate. Consequently, we conclude that the initial conditions are very important for the crystal growth of the as-deposition poly-Si.