The Effect of P Concentration on Gettering of Multicrystalline Si Wafers

Silicon (Si) wafers cut from an industrially grown ingot were subjected to phosphorus (P) gettering. The gettering was performed by coating the wafers with spin-on sources containing five different P concentrations and the wafers are subjected to a diffusion process at a temperature of 900 °C for 380 seconds. Thereafter, selected wafers were subjected to lifetime measurements. The effect of the gettering process on the distribution of selected metallic impurities near the wafer surface was determined in parallel by performing secondary ion mass spectrometry measurements on neighbouring wafers subjected to the same gettering processes. A clear effect of varying the P concentration on the lifetime and impurity distributions was observed. Below a certain level of P, gettering is no more an efficient tool for improving Si material quality