Here, Nd:YAG and excimer lasers were used to dope the carbide with N and Al, respectively. Mathematical models were developed for the temperature distributions in the wafers in order to understand the diffusion mechanisms occurring in the laser doping process. Since the carbide substrate attained its peritectic temperature (3100K) at irradiances of 80.6 and 61MW/cm2 for Nd:YAG and excimer lasers, respectively, lower irradiances were used to achieve solid-state diffusion. The Nd:YAG laser doping process doped N to a depth of 800nm, while the KrF excimer laser doping process produced Al dopant depths of 200 and 450nm for differing numbers of laser pulses. Two distinct diffusion regions, near-surface and far-surface, were identified in the dopant concentration profiles; indicating the operation of different diffusion mechanisms in the 2 regions. The effective diffusion coefficients of N and Al were determined for both regions and were found to be equal to 2.4 x 10−5 and 9.2 x 10−6cm2/s in the near- and far-surface regions for N, respectively, and 1.2 x 10−5 and 1.3 x 10−6cm2/s in the near- and far-surface regions for Al, respectively. The calculated diffusivities were at least 6 orders of magnitude higher than the typical values for N and Al. This indicated that the laser doping process significantly enhanced the diffusion of dopants in SiC.

Laser-Enhanced Diffusion of Nitrogen and Aluminum Dopants in Silicon Carbide. Z.Tian, N.R.Quick, A.Kar: Acta Materialia, 2006, 54[16], 4273-83