Multiscale FE modeling concepts applied to microelectronic device simulations

In order to investigate the reliability of power semiconductors under overload conditions, a detailed thermal analysis concerning temperature distribution and three dimensional heat flow of MOSFET devices is required. Thermal finite element simulation methods have the potential to provide this information but are limited due to computational constraints when approaching multi-scale models. Unfortunately, a typical power MOSFET device has a highly complex layer structure close to the junction in the sub-micrometer range while in lateral direction the active region of the MOSFET extends to the millimeter range. In that case, the standard FE method is limited due to its requirement of conforming meshes. The methods presented in this paper introduce homogenization concepts as well as nonmatching grid techniques to overcome this limitation. With the aid of homogenization methods, effective orthotropic material parameters are obtained. Nonmatching grids allow to embed complex device structures, such as temperature sensors, in full detail within the macroscopic full chip model. Both concepts are applied and verified on a dedicated power semiconductor test structure.