DIFFUSION AND LIFETIME ENGINEERING IN SILICON

Diffusion mechanisms in crystalline silicon are reviewed emphasizing the role played by the structural defects like vacancies and self-interstitials. These defects control the diffusion process of some transition metals, such as Au and Pt, which undergo fast long-range diffusion as interstitials and become substitutional by replacing a Si atom in a kick-out reaction. The influence of boundary conditions and sample surfaces on the concentration profiles of these metals are analysed in detail. These profiles can be precisely tailored using ion-implantation to achieve a low fluence diffusion source. Fine tuning of the metal profiles is shown to improve greatly the trade-off between dynamic and static characteristics of some silicon power devices like metal-oxide-semiconductor field effect transistors. Moreover, the possibility to obtain a preferential reduction of lifetime by metal doping in a selected