An examination of athermal, photonic effects on boron diffusion and activation during microwave rapid thermal processing

This paper details work demonstrating the effect of athermal mechanisms involving optical and microwave illumination on the flux of dopants in ultra-shallow doped Si layers. Optical illumination has a significant, yet transient, effect on the formation of ultra-shallow junctions in B doped Si. Rapid thermal annealing was performed on both B-only and BF₂ implanted silicon samples. During microwave annealing, the optically illuminated samples illustrated a greater amount of B diffusion with respect to the non-illuminated samples for the B-only implanted Si, while the reverse was true for the BF₂ implanted samples. In addition to a deeper junction depth, the illuminated samples had a lower sheet resistance. Both illuminated and non-illuminated samples fall on the same Rs-Xj curve, indicating a shift in optimal anneal temperature and not an improvement in junction formation. The relative difference in the diffusion depth of B between the illuminated and non-illuminated samples was dependent on the oxygen concentration in the ambient during the anneal.