Thermal redistribution of impurities in silicon‐on‐sapphire: Theoretical development

A solution to the problem of redistribution of impurities in a finite silicon slab has been determined using the Green’s function for the diffusion equation in a transformed coordinate system. This solution can be used to predict the spatial distribution of the impurity concentration profiles corresponding to different values of time during drive‐in and thermal oxidation occurring in the fabrication of silicon‐on‐sapphire (SOS) devices. A computer program based on the solution has been developed and applied to illustrative examples where the initial impurity distributions arise from single and double ion implants of boron or phosphorus in silicon. Numerical results which predict the redistribution of these initial distributions during thermal oxidation are presented. In a future paper, theoretical predictions based on the solution of the present paper will be used to correlate experimental data on the redistribution of impurities in SOS.