Quantifying High Temperature MEMS Micro Strain Relaxation Kinetics
High-temperature MEMS micro-strain relaxation follows stretched exponential kinetics driven by Coble creep, requiring in-situ Raman verification above 400°C.
Raman Micro-Spectroscopy
Spectroscopic Analysis
Laser-based analytical techniques provide non-destructive, high-resolution chemical and structural information from micron-sized regions of a sample. This spatial determination is accomplished with raman micro-spectroscopy, which couples an optical microscope to a Raman spectrometer. The technique evaluates phase distribution, crystal quality, molecular orientation and localized material composition.
Measurement Principle
Monochromatic excitation light interacts with the molecular vibrations of the specimen, yielding inelastic scattering that shifts the wavelength of the return signal. The resulting spectrum acts as a fingerprint that discloses the chemical bond types present in the focal volume. Because the laser focuses through a microscope objective, the lateral resolution can reach sub-micron limits.
Stress Measurement
Mechanical stress within the material distorts the crystal lattice, which alters the vibrational frequencies and shifts the peaks in the acquired spectrum. In microelectronics, raman micro-spectroscopy evaluates the localized stress fields surrounding silicon through-vias and micromachined structures. This capability allows the non-contact tracking of mechanical strain with high spatial precision.
System Calibration
Quantitative strain evaluation requires precise calibration of the spectrometer wavelength scale using a certified neon emission lamp or a monocrystalline silicon reference band at 520.7 inverse centimeters. Environmental temperature drift during measurements must be compensated to prevent artificial peak shifting. This stabilization is verified by acquiring periodic reference spectra from a standard reference material before and after each measurement run, assuring that any deviation in the peak position is correctly attributed to material strain rather than system instability.