Phosphorus‐Doped Polycrystalline Silicon via LPCVD: I . Process Characterization

Abstract

We have studied the low pressure chemical vapor deposition (LPCVD) process as applied to the preparation of in situ phosphorus‐doped polycrystalline silicon films. Thickness profiling, electron microprobe, and mass spectrometry have been utilized in the characterization of this process. The addition of phosphine as the dopant bearing precursor molecule was found to result in a factor of 25 decay in film growth rates relative to the intrinsic LPCVD process. The physical and chemical characteristics of samples prepared in this manner are shown to be a strong function of local reactor geometry, with growth‐rate variations of a factor of two within a wafer commonly observed. Mass spectrometry data is presented supporting the proposal that phosphine passivates the silicon surface, and the implications of this phenomenon for altering silicon growth kinetics are discussed. A model is presented accounting for the growth‐rate variations observed within individual wafers, as well as for the sensitivity of the phosphine‐doped process to system geometry.