Effects of different laser sources and doping methods used to dope silicon carbide

Abstract

An excimer laser and Nd:YAG laser were chosen to dope SiC polytypes by nitrogen (n-type dopant) and aluminum (p-type dopant). In the case of p-type doping, three different doping methods, i.e., (i) doping from trimethylaluminum (TMA) precursor, (ii) an effusion–diffusion process and (iii) doping from Al powder precursor, were used and compared. The results show that Nd:YAG laser treatment provides higher dopant concentration and deeper dopant penetration depth than the excimer laser treatment for both nitrogen and aluminum dopants. This difference is attributed to different heating mechanisms for the two kinds of laser sources. In the case of p-type doping by excimer laser, the Al dopant concentration distributions along the depth of wafer are different for the three doping methods. Method 3 produces the highest Al concentration, which is related to the high concentration of Al due to the formation of a molten aluminum film at the wafer surface. The Al concentration obtained by the effusion–diffusion process (method 2) is higher than that obtained by the TMA precursor method due to a higher Si vacancy concentration created by the effusion process. Shallow and deep junctions fabricated by an excimer laser and a Nd:YAG laser can be used for different semiconductor devices.