Dopant deactivation and diffusion in silicon in the presence of metal silicides.

摘要

Current transistors and integrated circuits contain many polycrystalline materials, including polysilicon in the gates and metal silicides in contact with doped poly- and single crystal silicon. Because dopant distribution and activation affect device properties, it is important to understand dopant behavior within and in the presence of these polycrystalline materials.; A new, more physically realistic model for diffusion in polycrystalline materials is presented and described. This model consists of continuous materials' properties, while also considering distinct grains and grain boundary regions of influence. The model is implemented in software, and simulations are performed to show dopant diffusion through multi-grained structures. The resulting dopant distribution profiles are closer to experimental results than profiles achieved using previous models of diffusion in polycrystalline materials.; Experimental results show, however, that long-range dopant diffusion cannot account for changes in the properties of certain silicided devices. Experimental results are presented which show dopant deactivation in polysilicon in the presence of metal silicides, and a theory is proposed to explain the observed effect. The adverse consequences of dopant deactivation in the presence of silicides on device properties are shown in computer simulations.