High-resolution thermoreflectance microscopy

Abstract

ABSTRACTWe present very high-resolution thermal microscopy using the technique of thermoreflectance, a non-contact measurement of the temperature in and around active semiconductor devices. By measuring the local change in reflectivity and comparing to the optical index versus temperature for the interface materials, thermoreflectance can determine the local temperature distribution. Thermoreflectance allows us to work at wavelengths much smaller than those used in typical blackbody imaging, and thus the spatial resolution is significantly improved over that of traditional thermal microscopy. In our experimental setup, we have a confocal scanning optical microscope with a tunable laser, where reflected light is detected by a silicon photodiode in a heterodyne scheme. The sample consists of a 600 nm wide poly-silicon wire embedded in silicon dioxide on top of a silicon substrate. Varying the amount and temporal shape of the current through the poly-silicon wire, we generate a controlled thermal profile to test the imaging capability. Our preliminary results indicate sub-micron thermal resolution.