Numerical simulation on controlling the front-side temperature of thinned SiC substrate during ohmic contact to Ni or Ti using back-side laser annealing

Abstract

This study numerically simulates the temperature fields of metal/4H-SiC ohmic contacts during back-side laser annealing, especially once the 4H-SiC substrate has been thinned. The results show that the front-side temperature can be easily controlled by adjusting laser parameters with the formation of ohmic contact when Ni was used as the contact metal before and after thinning. However, the front-side temperature posed a problem in the case of Ti/SiC contact because of the lower capability of thermal conduction of Ti compared with that of Ni. The pulse width of the laser had no obvious effect on front-side temperature because the heat-affected depth in the substrate due to pulse width was limited at the same energy density. In addition, reducing the thickness of the Ti film to below 100 nm helped avoid melting of the Ti surface. Lastly, the thermal budget maps of Ti (30 nm)/SiC (30  μm) and Ni (100 nm)/SiC (30  μm) contacts were protracted, in which the energy density and pulse width of the laser could be obtained for a lower front-side temperature. This method can be used to control the whole temperature fields induced by laser annealing after thinning the SiC substrate. This study also discusses the size effect of the physical properties of the metallic contact films.