Refractive Index, Free Carrier Concentration, and Mobility Depth Profiles of Ion Implanted Si: Optical Investigation Using FTIR Spectroscopy

Fourier transform infrared (FTIR) spectroscopy combined with a computer code for optical analysis of multilayer structures is implemented in this study as a nondestructive depth profiling tool. High-energy (1.2 MeV) P implanted Si is examined in the as-implanted state and after annealing at 950 degrees C. Ion implantation led to the formation of a buried amorphous layer with transition regions that can be described by half-Gaussian segments. Annealing yielded a free carrier concentration profile that can be modeled by a Pearson distribution as confirmed by spreading resistance profilometry (SRP). The proposed optical analysis model incorporates mobility variation versus depth, and the validity of replacing the varying mobility with a constant average value in the analysis of FTIR data is tested. (c) 2008 Optical Society of America.