A Study of Temperature Distribution in SOI-Smart Power Devices in Transient Conditions by Optical Interferometry

Siemens Corporate Research and Development ZFE T KM6Otto-Hahn-Ring 6, D-81739 Munich, GermanyAbstract1. Introduction Silicon-On-Insulator (SOI) by Direct Wafer Bonding [1] has become an attractivetechnique for the fabrication of smart power devices. Self-heating effects in such structuresare, however, more critical compared to bulk devices due to a reduced heat removal acrossthe buried and trench oxides [2,3]. Power dissipation could cause localized temperatureincrease in the device active region, which may influence the device performance andreliability. In monolithic chip technology, the amount of heat laterally spread from the powerdevices across the sided trench oxides is also important as it may influence thecharacteristics of a nearby CMOS control circuit. In this paper we present an analysis of thetransient temperature variations inside and outside the SOI well of smart power devicesobtained by optical interferometry measurements. 2. Measurements The measurements have been carried out on trench isolated Lateral Double-diffused(LD)MOSFETs [4]. The SOI wafer structure consists of a highly doped p