Failure And DPA Of Silicon-based MEMS Comb-type Capacitive Accelerometer

The application and market of MEMS technology are growing and having huge potential for development because of its characteristics that it can be mass-produced and it is low cost, low power consumption and integrated, while the reliability of MEMS devices is a key to successful application, so it is important to carry out reliability research of MEMS.In reliability studies, failure analysis and destructive physical analysis (DPA) are important part of the produce reliability project. Despite the failure mechanism of Micro Electromechanical System(MEMS)has been numerous studies and related theory has also been presented, there are still a lot of failure mode and mechanism need further study because of the complexity of MEMS structure, the diversity of its product and the constant updates of MEMS technology, and the DPA of MEMS is still lack of standard at home and abroad, it is need to conduct failure analysis on MEMS and study DPA technology to improve relevant standard content and ensure the reliability of MEMS devices .Silicon-based MEMS comb-type capacitive accelerometer was studied in this thesis. By using Scanning Electron Microscopy (SEM), X-Ray Inspection System, Scan Acoustic Microscopy (SAM), Energy Dispersive X-ray spectroscopy (EDX), microsection inspection and analysis, package gas analysis and electrical test, and through a series of environment tests, failure analysis and DPA study were conducted on samples with different dimensions.Failure study on Silicon-based MEMS comb-type capacitive accelerometers that have failed in the process was conducted, its main failure modes of structure and package were determined. The verified failure modes show that main failures of this kind of MEMS products were the failures occurred in process. Moreover, the package failures of this kind of devices were leakage and failures occurred in assembling process. The adhesion, pollution, comb fracture and warping comb were aseessed as standard defect.Failure analysis of Silicon-based MEMS comb-type capacitive accelerometer under shock was conducted, its failure mechanism was analyzed and its main structural failure mode was verified as cantilever fracture, and mode analysis result by ANSYS was the same with the experimental result. While the package failures were still leakage and failures occurred in assembling process. Moreover, experimental results show that the particle impact noise (PIND) testing can be applied to DPA test of MEMS.The reliability of MEMS samples with special thin cantileverand and different sizes'scratch in cantilever respectively were evaluated under a series of environment tests such as high and low temperature, temperature shock, humidity tests mechanical vibration and mechanical shock . At last , thinner than 1 / 2 standard cantilever size was assessed as DPA standard defect, which as a criterion to decide whether failure.