Inv estigation by the Method of Images of the Heat Flux Distribution at the Semiconductor-Substrate Interface in Transistor Structure from a Point Heat Source Located at the Passivation-Semiconductor Interface

Abstract

Previously the problem of the heat flux distribution at the semiconductor-substrate interface in the semiconductor-substrate transistor structure with adiabatic boundary condition on top of semiconductor was solved analytically. The method of images for two cases of a point and a linear heat sources located on the top of semiconductor layer was used to solve this problem. The substrate was considered as a half-space adjacent to the bottom of the semiconductor layer unlimited on the sides. It has been shown that even in the case of a perfect heat sink into substrate, the heat flow transverse dimension at the semiconductor-substrate interface has the order of thickness of the semiconductor layer. And with decreasing thermal conductivity of the substrate, this transverse dimension increases substantially. In our work, so far only for the case of a point heat source, a solution of a more general problem of heat propagation in the passivation-semiconductor-substrate transistor structure is obtained. Using the method of images, we calculate the transverse dimension of the heat flux at the semiconductor-substrate interface depending on the value of the thermal conductivity of the substrate for different values of the thermal conductivity of passivation. According to our study, the appearance of the heat sink into passivation leads to an increase in the transverse dimension of the heat flow at the semiconductor-substrate interface, although the proportion of heat going into the substrate decreases. Our research should help to optimize the design of transistor structures taking into account the heat transfer into passivation, which is relevant, for example, for high-power transistors based on wide band gap semiconductors, such as GaN and SiC, when the heat dissipation in the active region of the device, located close to passivation, is very high. In addition, our results confirm the previously developed practical recommendation for TCAD simulations with accounting for self-heating effect.