Measurement of nonthermal illumination-enhanced self-diffusion in silicon

There has long been suspicion that the strong lamp illumination required for annealing after ion implantation may non-thermally influence the diffusion of dopants . Identification of such effects is difficult in conventional RTA geometries because lamps provide both heating and photostimulation, and because the interpretation of conventional dopant diffusion experiments is impeded by complex dopant-defect interactions. We have circumvented these problems with a new experimental design in which heating and illumination can be decoupled. Data interpretation has been simplified by examining the motion of isotopically labelled ³⁰Si tracer in an epitaxial ²⁸Si matrix using SIMS depth profiling. Results show that for n-type Si, self-diffusion rates are increased non-thermally by more than an order of magnitude for modest illumination intensities of 0.7 W/cm². There is no comparable effect for p-type material, however.