Strain energy imaging of a power MOS transistor using speckle interferometry

Mechanical characterization of electronic devices is often quite uneasy; most of the techniques used require a contact with the sample under study. In this paper, we propose an optical noncontact interferometric imaging method to study the thermomechanical behavior of running devices, and in particular, to deduce the corresponding elastic strain energy. This analysis will permit us to localize the zones of fragility of the device. Results obtained on a power MOS transistor to detect the region of maximum elastic strain energy are presented. It is in particular adapted in microelectronics applications to detect stress accumulation due to dilation coefficient mismatches when assembling microchips.