Thermal Oxidation of Heavily Phosphorus‐Doped Thin Films of Polycrystalline Silicon

Abstract

The thermal oxidation of polycrystalline‐silicon films deposited by low pressure chemical vapor deposition and doped to solid solubility with phosphorus has been studied over temperatures ranging from 750° to 1100°C, for durations of 10 min to 88 hr. It has been observed that heavy doping increases the oxidation rate so that it is similar to that of single crystal silicon, however, enhancement is more like that of polycrystalline silicon. Calculation of rate constants was done based on the linear‐parabolic oxidation model. Reasonable values of the parabolic rate constant but anomalous values of the linear rate constant were obtained. Based on these observations and conductivity of the residual layer of the polycrystalline‐silicon film it can be concluded that because of the presence of the grain boundaries several additional factors, such as dopant segregation and higher diffusivity at the grain boundaries, different oxidation rates of the grains and the grain boundaries substantially alter the kinetics of oxidation.