3-DIMENSIONAL CONCENTRATION PROFILES OF HYBRID DIFFUSERS IN CRYSTALLINE SILICON

The diffusion of ion-implanted Au, Pt, and Zn in crystalline Si has been investigated. The implantation was performed in photolithographically defined areas of the wafer and a spreading resistance technique was used to measure the three-dimensional concentration profiles of the metal atoms after high temperature diffusion anneals. We found that the lateral spread under the mask is larger than the vertical diffusion, especially on the sample side opposite to the implanted diffusion source. All the significant features of the measured profiles can be explained as a consequence of the kick-out mechanism of diffusion for these transition metals. In fact, the peculiar shape of the concentration profiles is determined by the interplay between the influx of interstitial metal atoms and the outflux of silicon self-interstitials generated by the kick-out reaction. Despite the high lateral diffusion, it will be shown that by a suitable combination of implantation fluence and annealing temperature it is possible to limit this lateral spread inside approximately 200 mum, while maintaining a high metal concentration in the region under the implanted area. This demonstrates the possibility of using transition metal diffusion to control minority carrier lifetime in a selected area of a semiconductor device.