Formation of aminosilanes in the hot-wire chemical vapor deposition process using SiH4-NH3 gas mixtures

Abstract

Vacuum ultraviolet laser single photon-ionization coupled with time-of-flight mass spectrometry has been used to detect the gas-phase reaction products from the HWCVD reactor with SiH 4 -NH 3 mixtures with various partial pressure ratios ranging from 1: 1 to 200 : 1 for NH 3 : SiH 4 . The identity of the products depends strongly on the relative amounts of SiH 4 and NH 3 in the mixture. Low NH 3 content favors the production of disilane and trisilane. When the NH 3 content is high, the formation of aminosilanes becomes the primary pathway. The production of sufficient amount of NH 2 (or ND 2 ) radicals is found to play a key role in the competition between the two pathways. The formation of aminosilanes when using mixtures with an ammonia to silane pressure ratio greater than 49 : 1 is confirmed through the use of the isotopomer ND 3 in place of NH 3 in the gas mixtures. A stepwise amination reaction scheme, initiated by the reaction between the SiH 3 and NH 2 radicals, is responsible for the formation of aminosilanes. The effect of filament temperature on the formation of aminosilanes and di-/trisilane has also been investigated.