Mass spectrometric study of gas-phase chemistry in the hot-wire CVD processes of SiH 4/NH 3 mixtures

Abstract

The gas-phase reaction products of SiH 4, NH 3 and their mixtures from a hot-wire CVD chamber were investigated using laser ionization time-of-flight mass spectrometry. Both vacuum ultraviolet laser single photon ionization and laser-induced electron impact ionization were used. The main products observed from a 50% NH 3/He sample were H 2 and N 2. The study of an NH 3/SiH 4 mixture ( P NH 3 : P SiH 4 = 100:1) has shown that the NH 3 dissociation on the filament was suppressed by the presence of SiH 4 in the system. Signals from Si(NH 2) 4 and Si(NH 2) 3 species were identified as products from the 100:1 NH 3/SiH 4 mixture. The spectrum for a 1:1 NH 3/SiH 4 mixture was dominated by mass peaks characteristic of SiH 4 chemistry in the reactor, i.e. H 2, Si 2H 6, and Si 3H 8, at low temperatures. The extent to which the decomposition of NH 3 is suppressed is enhanced with more SiH 4 molecules in the system.