Oxidized Boron Nitride Wafers as an In-Situ Boron Dopant for Silicon Diffusions

Abstract

Hot‐pressed 93% boron nitride wafers when properly oxidized and used as an in situ boron dopant in open‐tube silicon diffusions are capable of providing sheet resistance tolerances of ±1–2% across a silicon wafer and ±4% within a run and from run to run. Although for the experimental conditions studied silicon sheet resistance variations were not expected to be a function of diffusion ambient, ambient flow rate, or source to silicon spacing the contrary was found to be true and the relationships opposite to that intuitively expected. By correlating sheet resistance, impurity profiles, and ellipsometric measurements the observed dependence of sheet resistance vs. ambient, ambient flow rate, and source to silicon spacing is explained in terms of phase formation.