Non-destructive internal inspection of MEMS bonded wafer pairs via acoustic micro imaging is useful in finding, characterizing and eliminating anomalies and defects.
During product development, acoustic inspection is helpful is modifying processes to avoid defects. During production, acoustic inspection spots rejects and identifies process drift.
The ultrasonic transducer that scans the wafer pair pulses UHF ultrasound into the top surface and receives the return echoes. Pulse-echo occurs thousands of times per second as the transducer moves across the surface. Each scanned x-y coordinate yields one pixel in the acoustic image which, in the high resolution typically used for MEMS wafers, consists of millions of pixels.
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