Preparation of High-Quality Undoped Microcrystalline Silicon with High Deposition Rate Using Mercury-Sensitized Photochemical Vapor Deposition Method

Abstract

We prepared undoped microcrystalline silicon films (µ c- Si:H) using a mercury-sensitized photochemical vapor deposition system under various film deposition conditions of SiH4/(SiH4+H2) gas ratio and total gas flow rate, and investigated the dependence of the film quality on the deposition conditions in order to obtain high-quality undoped microcrystalline films at a high deposition rate. Up to a SiH4/(SiH4+H2) gas ratio of ∼0.1, the crystallite size of the µ c- Si:H films decreased linearly as the ratio increased, but the volume fraction of crystallites remained constant at about 80%. The dark conductivity of the films was very low, in the range of 10-7–10-6 Scm-1 under nearly all experimental conditions, and so a high photosensitivity of ∼550 was obtained without the addition of a dopant gas such as diborane. In addition, a high deposition rate of ∼30 Å/min was obtained at a low total flow rate of 21 sccm. No degradation of the microcrystallinity was observed for the low total flow rate.