The possible benefits of P-based gettering applied to crystalline Si wafers were evaluated. The gettering process was achieved by forming porous Si (PS) layers on both sides of the Si wafers. The PS layers were formed by the stain-etching technique, and P diffusion using liquid POCl3-based source was done on both sides of the Si wafer. The realized P/PS/Si/PS/P structure undergoes a heat treatment in an infra-red furnace under an O2/N2 controlled atmosphere. This heat treatment allows P to diffuse throughout the PS layer and to getter eventual metal impurities towards the P doped PS layer. The gettering effect was evaluated using four probe points, Hall effect measurements and the light beam induced current technique. These techniques enable to measure the density and the mobility of the majority carrier and the minority carrier diffusion length (Ld) of the Si substrate. It was noticed that the best gettering was achieved at 900C for 1.5h of heat treatment. After gettering impurities, an apparent enhancement of the mobility and the minority carrier diffusion length was found, when compared to the reference substrate.

Gettering Impurities from Crystalline Silicon by Phosphorus Diffusion using a Porous Silicon Layer. N.Khedher, M.Hajji, M.Hassen, A.Ben Jaballah, B.Ouertani, H.Ezzaouia, B.Bessais, A.Selmi, R.Bennaceur: Solar Energy Materials and Solar Cells, 2005, 87[1-4], 605-11