Due to the carrier mobility changes with the mechanical loading and its small size, the MOSFET (metal-oxide-semiconductor field-effective-transistor) has the potential to be a suitable chip stress monitoring tool for microelectronic packaging. In this work, a complete and accurate approach to calibrate the coefficients for both types of MOSFET stress sensors under thermal and mechanical loadings was investigated quantitatively. Through data from different measurement modes on different types of MOSFET, the optimal experimental methodology was next proposed for the sensor applications on packaging stress extraction. The thermomechanical coupling coefficients for the selected experimental mode were finally extracted so that packaging stress measurements with MOSFET under elevated temperature can be performed more accurately.

It is well known that the CTE mismatch and the hygroscopic swelling mismatch in a plastic packaging lead reliability issues so that a suitable extraction methodology on packaging stress and failure parameters are needed. To this end, we first designed and made the piezoresistive stress sensors for packaging stress measurements and performed the sensor calibrations. Test chips were next packaged into a typical plastic packaging and the hygroscopic stress were measured. Finally, a reliability test was performed to extract the long-term effects and the reliability parameters. It is concluded from the works that the hygroscopic mismatch stress is about 50 MPa and it is significant for the packaging. It is also concluded that the Weibull reliability model is suitable for the PBGA packaging, and the Weibull parameters were successfully extracted.

No abstract