LBIC INVESTIGATION OF PHOSPHORUS GETTERED MULTICRYSTALLINE SILICON WAFERS

Abstract
In multicrystalline silicon the interaction of dissolved impurities with extended crystallographic defects limits the effective minority carrier diffusion lengths L_n. External gettering by phosphorus diffusion near the surface is used to remove metallic impurities from the bulk of P type silicon wafers. It was found that L_n increases drastically after gettering at 850°C for 120 or 240 mn. SIMS analysis indicates that iron, copper and nickel are accumulated in the phosphorus doped regions and LBIC scan maps at λ = 940 nm indicate that the improvement of L_n results of the neutralization of intragrain and grain boundary recombination centers. It is concluded that phosphorus gettering removes dissolved and segregated impurity atoms.