Photoeffects on the fluorination of silicon. II. Kinetics of the intial response to light

Abstract

When a silicon surface etched by XeF2 is illuminated with laser radiation, strong changes are observed in product formation rates. Initial rates of change of the products SiF, Sif2, SiF3, and SiF 4 have been determined as a function of doping, pressure, and light intensity. Analysis of the kinetics has provided new insight into the mechanism by which radiation influences the etch rate. In particular, it has been found that initial rates of the species SiF4, SiF2, and SiF exhibit an approximately quadratic dependence on the laser intensity, while SiF3 appears to depend on its fourth power. It is proposed that trapping of electrons and holes by flourine and silicon flouride centers at or near the surface greatly increases their reaction rate. Modeling confirm this picture and provides some estimates for the relative magnitudes of rate constants for essential process.