Characterization and TCAD Modeling of the Lateral Space Charge Accumulation in Epoxy Molding Compound in Packaged HV-ICs

The reliability of high-voltage (HV) integrated circuits (ICs) can be significantly affected by space charge accumulation at the interface between the passivation layer and the epoxy molding compound (EMC) which acts as encapsulation material. The incorporation of moisture, which significantly increases the EMC conductivity, can lead to a stronger distortion of the electric field with a consequent breakdown instability. Moreover, the distance of the integrated-circuit active regions from the peripheral bond pads and wire would require a thorough optimization. To investigate the role played by the EMC under such conditions, a dedicated test chip made by an array of charge sensors covering short distances from bon-pads has been manufactured. A novel technique has been used to estimate the amount of space charge in the EMC independent of the bias applied to the bond pads. The outcome of the experiments has been explained by performing 2-D TCAD simulations of the structure under investigation which accurately account for the charge transport mechanisms of the EMC.