In-Package Measurements of Space-Charge Accumulation in Epoxy Mold Compound Through Silicon Integrated Charge Sensors

The space charge dynamics in Epoxy Molding Compounds (EMCs) is critical for the reliability of high-voltage integrated circuits, especially under wet conditions. This work presents a novel approach for monitoring negative space charge accumulation in EMCs using integrated p-channel silicon charge sensors. The sensors, embedded underneath the EMC layer, allow for real-time detection of electrostatic potential variations by tracking changes in the sensor drain current. A calibration procedure based on the Enz-Krummenacher-Vittoz model enables conversion of the measured current into voltage, thereby quantifying the potential at the EMC/passivation interface. Experimental results under dry and wet conditions demonstrate that moisture significantly enhances EMC conductivity and accelerates charge transport. Additionally, the study shows that negative charge accumulation is slower than positive one, offering new insights into the charge transport mechanisms within EMCs. This method provides a promising tool for assessing high-voltage integrated circuits in-package reliability.