Post-Diffusion Gettering Effects Induced in Polycrystalline Silicon

Large grain polycrystalline silicon wafers have been subjected to post~annealing (900 °C/45 ruin) after POCI3 pre-diffusion at different temperatures. For the first time we have investigated the effect of the furnace starting and quenching temperature on the gettering efficiency. The optimisation of thermal cycle parameters include the determination of the best combination of starting temperature, of post-annealing, heating rate, cooling rate, postannealing temperature (duration), quenching temperature and POCI3 diffusing condition result in an increase by 275$~ of the minority carrier diffusion length. The second advantage of this post-annealing is the improvement of the homogeneity of activated phosphorus distribution and of the electrical properties.