The low-temperature anodization of silicon in a gaseous plasma

Abstract

A comprehensive investigation of the low-temperature anodization of silicon in RF and microwave oxygen plasmas is discussed. A comparison of the growth results and ion signals observed, using quadropole mass spectrometry, indicates a strong correlation between the growth rate and the presence of O/sup -/ ions in the plasma. Characterization of parameters such as pressure, electrode spacing, and current density has allowed wafers up to 4-in. diameter to be anodized with good growth rates (0.3 mu m/h) and excellent oxide uniformity, using low temperatures (<or=600 degrees C), low input power densities ( approximately 59 W-cm/sup -2/), and low current densities ( approximately 7 mA-cm/sup -2/). Oxide properties such as etch rate and refractive index were found to be indistinguishable from thermally grown oxides. Optimization of anneals and the use of a halogen gas enables plasma oxides with high breakdown fields (10-11 MV/cm), an interface trap density of approximately 5*10/sup 10/ cm/sup -2/-eV/sup -1/ at midgap, and a fixed oxide charge of 6*10/sup 10/ cm/sup -2/ to be fabricated without resorting to high-temperature (>or=600 degrees C) processing.<<ETX>>