CLUSTERING, PRECIPITATION AND DIFFUSION IN ION-IMPLANTED SILICON

The trend towards shallow junctions and high doping levels in present and future submicrometre semiconductor devices means that diffusion mo dels, based on the assumption that dopant mobility is due entirely to the motion of single dopant atoms embedded in a semiconductor matrix, can no longer describe adequately the complex features which appear in measured profiles [1, 2]. These 'anomalous' profile shapes have been attributed to many different effects, including spatial distributions of point defects and dopant clustering [3]. In this work we examine th e purely statistical effects which arise from the most general feature s of clustering, precipitation and diffusion of dopants during ion imp lantation and high-temperature annealing, and the implications that th ese have for dopant distribution.