Raman spectroscopy was investigated as a method for the temperature and stress measurement in thermal MEMS devices. Calibrations of the Stokes Raman shift and the Stokes to anti-Stokes intensity ratio for doped samples were performed in order to calculate the temperature on simple polysilicon structures. Straight and serpentine micro-heaters of various sizes were fabricated from 2 micron doped polysilicon films on thick sacrificial oxide layers. Operating temperatures were measured at a range of input powers for devices attached to the oxide layer as well as released structures. Measurements show that all devices can exceed 400°C with the released devices requiring much less power, as expected. Temperature measurements using the Stokes shift method were compared to the conventional intensity ratio method in order to deduce the effects of thermal stresses on the temperature measurements. Using this method, it was found that thermal stresses could be qualitatively determined simultaneously with temperature in silicon MEMS devices. The effects of stress, however, results in less than a 10% difference in temperature over all of the input powers tested in this study.
Temperature measurements in confined swirling spray flames by vibrational coherent anti-stokes Raman spectroscopy
