The effect of filament temperature on the gaseous radicals in the hot wiredecomposition of silane

Filament temperature is an important parameter in the hot-wire chemical vap or deposition (HW-CVD) process, affecting both the growth rate and electron ic properties of the deposited thin films. Here we describe direct detectio n of gaseous free radicals produced as a function of filament temperature i n the HW-CVD of amorphous silicon from silane. Radicals have been identifie d using vacuum ultraviolet (VUV) single photon ionization (SPI), with 118-n m light formed by the 9th harmonic of a Nd:YAG laser. The major silicon-con taining gas-phase species identified by SPI during hot-wire activation of s ilane gas are Si, SiH3 and Si2H6. At the lower filament temperatures (900-1 300 degreesC) studied, consumption of silane is observed without significan t formation of Si-containing radicals. The concentration of Si rises rapidl y with filament temperature near T-til = 1300 degreesC before leveling off at temperatures above 1800 degreesC, while SiH3 and Si2H6 concentrations be come significant only at the highest temperatures. (C) 2001 Elsevier Scienc e B.V. All rights reserved.