Thermal analysis of novel buried insulator materials and geometries for the SOI LDMOSFET and resulting stability in electrical performance

Future market demands for Smart Power and System on a Chip (SOC) devices are forcing replacement of traditional bulk silicon technology for power semiconductor devices. The Silicon on Insulator (SOI) Laterally Diffused, Metal Oxide Silicon, Field Effect Transistor (LDMOSFET) is perhaps the potential power device technology for meeting these demands. However, SOI power semiconductors suffer from 'self-heating effects' due to the silicon dioxide (SiO2) insulating layer inhibiting heat flow and thus causing instabilities in device electrical performance.; The research hypothesis is that self-heating effects can be significantly reduced by using alternative materials and novel geometries for the buried insulator. Aluminum nitride (AlN) and amorphous diamond are the two materials examined. Three basic geometries are investigated: the homogeneous block, sandwich, and columnar configuration. A First Principles model of the buried insulator is developed, and the three-dimensional heat equation with boundary and initial conditions for each material and geometric structure is analyzed in a simplified operational thermal environment. Comparisons between the First Principles modeling results are made using measured data from the Seliger-Pogany and Arnold experiments which used SiO 2 as the buried insulator. Corroboration of thermal time constants and times to reach steady state are made using a combination of PSpice, MATLAB, FLEXPDE, and FEMLAB3 simulation tools.; Device improvements investigated in this research could lower the temperature rise for the buried insulator in SOI LDMOSFETS by one to two orders of magnitude, significantly stabilizing device electrical parameters and allowing higher operating temperature in a smaller package. The research concludes that the First Principles modeling and associated analysis are shown to be reasonably accurate in determining the time to reach thermal equilibrium in the buried insulator and improving the transient heat flow for the device. Results from the Seliger-Pogany and Arnold experiments also support conclusions drawn from these First Principles modeling equations. The research indicates that use of alternative buried insulator materials and geometries allows improved management of the self-generated heat and can significantly stabilize electrical performance of the device.; The proposed improvements could make the SOI LDMOSFET a viable candidate for Smart Power devices and for applications toward SOC technologies.