Stress induced by ultrasonic dissipation during thermosonic ball bond formation is measured in-situ using microsens inte-grated below test bonding pads. The devices are fabricated using a commercial CMOS process, exploiting p~+ diffusion as piezoresistive sensing material. We report time-dependent on-line measure-ments of the stress-induced resistance change. Higher harmonics of the microsensor signal are obtained. The influence of bonding force, ultrasound power, and bonding temperature was studied. The microsensor signal reveals significant process characteristics such as the minimal ultrasound level needed for bonding and the minimal dwell thime ennede to (a) start scrubbing and intermetallic phase formation and (b) attain maximum shear strength.
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