Comprehensive parametric analyses of thermally aged power MOSFETs for failure precursor identification and lifetime estimation based on gate threshold voltage

Thermal/power cycles are widely acknowledged methods to accelerate the package related extrinsic failures. Many studies have focused on particular failure precursor at a time and continuously monitored it using custom-built circuits. Due to the difficulties in taking sensitive measurements, the reported findings are more on the quantities requiring less sensitive measurements such as on-state resistance. In this paper, a custom-designed test bed is used to age a number of power MOSFETs and an automated curve tracer is utilized to capture parametric variations in I-V curves, transfer capacitances and gate charges at certain time intervals throughout the aging. The results suggest that the failure precursors which exhibit continuously increasing trend are the on-state resistance, body diode voltage drop, parasitic capacitances and threshold voltage. Based on the results, an exponential empirical model for the gate threshold voltage that fits successfully with the experimental data is proposed. Furthermore, Kalman Filter is employed to filter out the measurement noise and model uncertainties, which is also used to estimate the remaining useful lifetime of the degraded switches.