Effect of laser field and thermal stress on diffusion in laser doping of SiC

The electromagnetic field of lasers and non-equilibrium doping conditions enable laser doping of SiC with increased dopant diffusivity. Chromium, which acts as a double acceptor, has been laser-doped in SiC wafers. A thermal model is utilized to determine the temperature distribution at various depths of the wafer and a diffusion model is presented including the effects of Fickian diffusion, laser electromagnetic field and thermal stresses due to localized laser heating on the mass flux of dopant atoms. The dopant diffusivity is calculated as a function of temperature at different depths of the wafer based on measured dopant concentration profile. The maximum diffusivities achieved in this study are 4.61 × 10−10 cm2 s−1 at 2898 K and 6.92 × 10−12 cm2 s−1 at 3046 K for 6H-SiC and 4H-SiC, respectively. The maximum concentration is found to be 2.29 × 1019 cm−3 for 6H-SiC, which is two orders of magnitude higher than the reported value (3 × 1017 cm−3 solid solubility limit).