Effect of boron gettering on minority-carrier quality for FZ and CZ Si substrates

The gettering effect on boron-diffused FZ and CZ Si substrates was investigated by effective lifetime measurement with a chemical passivation technique. After removal of the boron-diffused layers, the effective lifetime increased about two times higher than initial values for p-type FZ Si substrates. However, thermal processes in O 2 and N 2 after boron diffusion degraded the effective lifetime drastically for both the substrates. These results suggest that lifetime killer impurities were gettered at defects in the P +-layers heavily doped by boron diffusion and diffused out into bulk regions because of lowering surface B concentration by the thermal processes. Heavy B concentration is needed to getter lifetime killer impurities.