Molding compounds for high breakdown voltage applications on power IC semiconductors

Power integrated circuits (IC) semiconductor devices are sensitive to any sort of process variations, device and package materials effects, and environmental changes and stresses that will affect their ability to withstand the maximum applied voltage during operation. For example, contact between the epoxy molding compound and the die surface can radically alter the electrical performance, especially after environmental stressing. Some of this could be mechanical, caused by thermal mismatch. Other reasons could be chemical interactions between the molding compound and the charges within the device passivation, which would also be greatly influenced by type. Unfortunately, there is a lack of literature available on electronic package effects on high voltage device behavior. In this study, the effect of molding compound on the breakdown voltage stability of a high voltage metal oxide semiconductor-field effect transistor (MOSFET), utilizing the RESURF (Reduced SURFace electric field) technique, was examined. Breakdown stability was tested by High Temperature Reverse Bias (HTRB) testing. Both compound and post-mold cure processes were found to affect the breakdown voltage, however, it also became clear that the compounds were not acting alone and it would be necessary to evaluate the chip passivation as well, and its interaction with the molding compound