${\rm CO}_{2}$ Laser Annealing for USJ Formation in Silicon: Comparison of Simulation and Experiment

In this paper, we compare the experimental and simulation results of the effect of laser annealing on boron implanted silicon using a CO₂ source and commercially available process TCAD tools. The main objective of this analysis is the prediction of the evolution of temperature distribution induced into the wafer during the laser irradiation below the melting threshold as well as its effect on boron diffusion and activation kinetics. A series of factors are considered along with the use of advanced heat transfer and dopant diffusion models provided by the TCAD tool to accurately prototype the effect of the CO₂ irradiation on temperature and dopant distribution. These include the nonuniformity of the incident laser beam, the strong dependence of heat capacity and thermal conductivity from temperature and, most importantly, the dependency of the absorptivity from temperature and dopant distribution, which requires the solving of dopant and heat transfer equations in a coupled and self-consistent way. Using surface temperature data obtained by pyrometry measurements, it was possible to calibrate and to verify the validity of the results. Experimental boron profiles were then used to compare with simulations in the transient regime where dopant diffusion just starts to occur. Both TCAD and experimental data confirmed previous suggestions that submelt CO₂ laser annealing is an efficient tool for profile engineering, allowing diffusionless activation of the plasma doped boron profiles.