Through the substrate, backside thermal measurements on active semiconductor devices using near IR thermoreflectance

Topside, thermal imaging on micro-devices using visible wavelength thermoreflectance has previously been demonstrated with sub-micron spatial and 100 mK temperature resolution. Now, by using a laser with a wavelength that is transparent to the substrate, the temperature of active semiconductor devices can be measured from the backside, through the substrate, using the same thermoreflectance technique. Point measurements on Si/SiGe based thin film micro-coolers grown on silicon substrates are performed using a 1310 nm laser. Temperature resolution better than 100mK has been achieved through a 200 μm substrate. Preliminary thermal images are also presented.