Nitrogen doped silicon films heavily boron implanted for MOS structures: Simulation and characterization

In this work we study the boron diffusion and its activation into recrystallized nitrogen doped silicon thin films (NIDOS) and we also discuss the influence of the chemical interaction between boron and nitrogen in NIDOS films. These films are deposited by low pressure chemical vapor (LPCVD) for the development of a P+ polysilicon gate for MOS structures. The reduction of boron diffusion with increasing nitrogen content is observed by SIMS profiles. SUPREM IV software is used in order to estimate the boron diffusion coefficients in NIDOS films. FTIR analyses show the appearance of a B-N complex whose density strongly depends on the annealing treatment in terms of temperature and duration. It is deduced through resistivity measurements and SEM observation that the formation of B-N complexes tends to degrade the electrical properties of polysilicon thin layers through the decrease of both electrically active boron and polycrystalline grains growth.