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

摘要

High quality polycrystalline silicon (poly-Si) films were deposited on SiO_2 substrate using hydrogenated microcrystalline silicon ( um c-Si:H) seed layer by very high frequency (182.5MHz) sputtering system and Chemical Vapor Deposition (CVD) system in pure Ar ambient at a temperature of 300 deg C.In this study,we investigated the correlation between the initial seed layer ocnditions and the growfn layer,and studied the nucleation proces. Electrical characteristics and surface roughness of hte grown layer as a function of film thickness and deposition rate will be shown.Grown layers were deposited on several kids of hydrogenated seed layers in pure Ar ambient.The resistivity and Hall mobility of the grown layer are 0.33 OMEGA cm and 7.5 cm~2/V sec respectivity for a film with thickness of 3000A.In this measurement,we found that the resistivity is lowr as deposition rate is slower,and when deposition rate is relativiely high,the resistivity increase with thickness.On the contrary,in the case of low depositin rate,eresistivity decreases as film thickness increases.For the deposition rate of 0.32 A/sec,the surface roughness ranges over 1.39 A-8.52 A.This is a very smooth surface compared to hydrogenated polycrystalline silicon films.The resistivity of tgrowth 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.