Transient thermoreflectance wafer mapping for process control and development: GaN-on-Diamond

Screening for optimal thermal performance of semiconductor wafers was developed based on a noninvasive thermo-reflectance technique. Temperature changes of the wafer surface, induced by a nanosecond pulsed laser absorbed into the near surface region, allows to extract critical thermal parameters such as thermal boundary resistances between epilayers or epilayers and substrate. These affect channel temperature in devices (RF, power, optoelectronics) once the wafer is fully processed. This is illustrated on GaN-on-diamond wafers which are presently being developed for ultra-high power RF applications.