Copper gettering in silicon by phosphorus and boron diffused layers and its impact on surface passivation

This study systematically investigates copper gettering in silicon by heavily doped n + and p + diffused layers fabricated on high-resistivity float-zone silicon wafers of both polarities, following intentional copper contamination of the wafer bulk. Experimental carrier lifetime analysis and photoluminescence imaging before and after dopant diffusion, corroborated by numerical gettering simulations based on the reported copper solubilities and diffusivities, demonstrate the gettering effect of n + and p + diffused layers for copper. The gettering effectiveness increases with increasing doping, as expected. Lightly doped regions exhibit limited gettering effects, for instance, an n + region with a sheet resistance of 150 Ω/□ can only getter 10% of the bulk Cu. This implies that such lightly doped surface regions may be insufficient barriers against copper in-diffusion from metallized layers to the silicon wafer bulk. Furthermore, the impact of gettered Cu on the surface passivation quality of SiN x -coated n + and Al 2 O 3 -coated p + regions was evaluated. For heavily doped samples, Auger recombination remains the dominant effect that masks potential Cu-induced degradation. For lightly doped samples, surface recombination was mostly limited by the applied spin-on-dopant rather than the gettered Cu.