Boron, phosphorus and aluminum gettering of iron in crystalline silicon: Experiments and modelling

A direct comparison of boron diffusion gettering, phosphorus gettering, and aluminum annealing gettering of iron is presented, using both experiment and simulation results. Float zone silicon samples were implanted with Fe and exposed to either B, P, or Al gettering at various temperatures for experimental measurements. The gettering model simulates dopant diffusion, segregation to doped layers, and diffusion of interstitial iron towards the gettering layers. The segregation model for Boron diffusion gettering agrees with the experiment results that boron diffusion gettering was completely ineffective at gettering Fe for diffusion temperatures above 850°C. Experiment results show that phosphorus diffusion gettering was effective in removing more than 90% of the interstitial iron across a range of temperatures and doses. Surprisingly, even relatively light phosphorus diffusions (145 Ω/□) were found to give very effective gettering. The phosphorus diffusion gettering model agrees reasonably with experimental results in terms of the amount gettered, but shows an opposite trend with temperature between 780°C and 850°C. Aluminum annealing gettering is very effective and the experimental detection limit prevents accurate measurements for comparison with the model.