Reliability problems due to ionic conductivity of IC encapsulation materials under high voltage conditions

In high voltage integrated circuits operating at high temperatures, the strong electric field spreading out from the high voltage bond pad via the encapsulation material is responsible for charge accumulation at the interface towards the nitride passivation layer. In low-voltage circuit blocks, this might lead to parasitic leakage currents. The physical background on the dynamics of the charge redistribution within the encapsulation material is discussed. With a proposed model, we show that the ionic conductivity is the root cause of the problem. Therefore, malfunction of the low voltage circuit blocks can be suppressed to a large extent by using very pure encapsulation materials.