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Wafer-level testing of surface-micromachined sensors provides new
challenges to the test community. Currently, there is no method available
for performing direct measurements to assess faulty micromechanical
structures. Most commercial methods use electrical measurements to deduce
the physical source of failures in the micromechanical structure. As a
result, the process of identifying various failure modes (electrical
measurements) and accurately mapping them to the underlying physical
failure mechanisms of the mechanical sensor becomes highly complex.
Several sources of failures that include particulates and stiction
complicate the situation even more. Here, we provide a case study of the
Analog Devices ADXL75 Accelerometer. One failure category called
stuck/tipped beams is investigated and a methodology is developed to
uniquely distinguish failures either caused by stuck or tipped beams. The
proposed method is easy to implement and the information obtained can be
critical for yield improvement.
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