Characterization and TCAD Simulation of the Electrostatic Potential Distortion in HV-ICs due to Losses in the Epoxy Mold Compound

The presence of space charge and leakage current within the epoxy-based mold compound (EMC) used as encapsulation material for high-voltage integrated circuits (HV-ICs) can significantly impact long-term reliability and performance of the devices when finally packaged. Moreover, the role of moisture, even if very little absorbed by the EMCs, can lead to a strong increase of the EMC conductivity, resulting in a larger electrostatic potential distortion when compared with the case of a perfectly dry insulating package. To directly measure the effects induced by space charge accumulation in dry and wet conditions, a dedicated test chip integrating a charge-sensor array has been manufactured and characterized. From the measured currents, the value of the electrostatic potential at the EMC/passivation interface has been accurately extracted. Moreover, the charge-sensor currents have been monitored during the discharging transient to investigate the concurrent coupling effects of the inner wiring and bondpads in discharge conditions.