Combining Low-Temperature Gettering with Phosphorus Diffusion Gettering for Improved Multicrystalline Silicon

We have investigated lowerature (≤500 °C) gettering in combination with phosphorus diffusion gettering with a view to improving poor quality multicrystalline silicon. Lowerature gettering applied after standard phosphorus diffusion gettering is found to provide a >40% improvement in minority carrier lifetime in samples from the top and bottom of an ingot. The best results are achieved at 300 °C with very long annealing times (>24 h). Improvements in the lifetime do not correlate with changes in interstitial iron concentration. Experiments are performed to assess whether the presence of a phosphorus-diffused emitter affects lowerature gettering, and results from sister samples show the lowerature gettering behavior is not affected by the existence of an emitter. Further experiments show that lowerature gettering prior to phosphorus diffusion results in a 20% higher lifetime after phosphorus diffusion. Lowerature gettering can, therefore, enhance lifetime even when used in conjunction with standard phosphorus diffusion gettering.