Study On Key Issues Of MEMS Mechanical Property Measurement And Reliability Analysis

MEMS mechanical property test and reliability analysis are significant in the research and development and even the industrialization of MEMS, and mechanical property test is the basis of reliability analysis. According to the detailed investigation on current research status of MEMS mechanical property test and reliability analysis techniques, phase-stepping microscopic interferometry is applied to characterize MEMS mechanical properties, based on which reliability of micro structures in vibration and shock environment is studied. The research work of the dissertation mainly includes the following aspects:1. The importance and the general situation of MEMS mechanical property test and reliability analysis are systematically investigated and analyzed, including classification of techniques, application fields, current status and development trend.2. To solve the problem that ordinary phase unwrapping methods in interferometry are not competent in measurement of surfaces with complicated profile or/and nonideal data areas, a breadth-first search phase unwrapping algorithm based on mask is presented. Inconsistent areas are flagged in mask images obtained using three optional methods and then ignored in phase unwrapping process to get continuous and correct surface profile information.3. In order to eliminate tilt errors in surface profile measurement of micro structures using microscopic interferometry, a robust approach based on least square method and coordinate conversion is proposed to compensate tilt errors, which is implemented by finding a reference plane with least squares fit and rotating the coordinate system to get the height information relative to the reference plane.4. A measurement technique to test MEMS mechanical properties based on phase-stepping microscopic interferometry and finite difference method is presented to extract Young's modulus and residual stress gradient of micro membrane. Unloaded micro cantilevers and cantilevers loaded with DC voltage are used as devices under test, of which surface deflection is measured by phase-stepping microscopic interferometry, and then the relationship between beam deflection and mechanical property parameters is analyzed using finite difference method. Property parameters are then acquired via comparing the measured and modeled deflection data and finding the best fitted values.5. Based on the test results of mechanical property parameters, the relationships and the variation regularities between micromachined SiC cantilevers' response to vibration and shock signals and amplitude, frequency and duration of shock pulse are analyzed with finite element analysis software. Using SiC cantilever arrays as test samples and standard vibration and shock testing systems as testing platform, a series of vibration and shock experiments are designed and performed to get the resistance capability of the cantilevers to vibration and shock from their failure situations under specific vibration and shock load.