Research on P/B Gettering of Upgraded Metallurgical Grade n-type Multicrystalline Silicon Wafers

The effect and mechanism of phosphorus/boron gettering of upgraded metallurgical grade(UMG) n-type mc-Si wafers were systematically investigated.The results show that the minority carrier lifetime and resistivity are improved greatly after getterring treatment.The lifetime is increased from 1.21 μs to 11.98 μs and 10.74 μs by phosphorus gettering and boron gettering at 1 000 ℃ for 4 hours and 950 ℃ for 1 hour thermal treatment,respectively.It is concluded that the improvements are mainly due to the heavy phosphorous and boron diffusion layer formed on the surface,which can absorb the heavy metal impurities and decrease recombination centers.