A nondestructive raman spectra stress 2D analysis for the pressure sensor sensitive silicon membrane

The residual stresses introduced by the bonding process has become a key effect for the MEMS product yield improvements. Many in-situ stress measurements have to destruct the devices. Raman spectroscopy is a nondestructive inelastic scattering measuring. Interpreting the silicon Raman frequency shifting can describe the stress location and intensity quantitatively in the lattice. The confocal microscopic observation can realize micrometer scale resolution. However, the limited visual field cannot provide the device stress distribution overview. In the meantime, the microscope loading platform displacement (only 100 μm) will introduce severe random errors (4 ± 1 μm) in the overlapping movements. Since the local stress intensity could be converted into a RGB gray pixel. Through the image mosaic algorithms, the measured local residual stress distribution maps (750 μm × 160 μm) could be stitched to an enlarged stress distribution map (750 μm × 340 μm). This methodology could not only expand the stress inspection overview(60 ± 2%), but also examine and eliminate the displacement random errors. The analysis results showed that the residual stresses were about 70 ± 5% of the simulation value. The uniform difference between the measured and simulated values indicated a trustable stress analysis.