Boron Instability in CVD‐Produced Borophosphosilica Films

Abstract

As-deposited borophosphosilica glass (BPSG) films undergo substantial relaxation during their storage in air. This work studies a mechanism of dielectric degradation, one effect of which is significant boron out-gassing at room temperature. This effect is discussed in terms of boron oxide charging when both dopants, B and P, are present in CVD-produced SiO 2 . The surface photovoltage technique is applied to the oxidized silicon to evaluate charge states on the Si/SiO 2 /BPSG interfaces after deposition. The characteristic change in the recombination lifetime and the depletion width in silicon subsurface confirms the contribution of charges from the BPSG to the silicon-oxide interface. The technique presented can be used to estimate the dopant out-gassing during annealing.