μ-Raman spectroscopy for stress analysis in high power silicon devices

Micron-scale characterization of mechanical stress is essential for physic failure studies in power devices. We report the use of Raman spectroscopy to measure mechanical stress in silicon power devices with spatial resolutions down to 500nm. μ-Raman measurements were realized on diode and Insulated Gate Bipolar Transistor (IGBT) cross sections unbiased and forward biased in order to map internal stress distributions. Temperature and stress contributions on Raman diffusion were deconvoluted fitting Full Width at Half Maximum (FWHM) and position of the stokes peak. For the first time, it was possible to quantify experimentally mechanical stress evolution during operation. These results give experimental data on thermo-mechanical coupling in power devices and could be able to support numerical models.