Polyimides for Power Device Applications

High voltage power semiconductor devices are required for such as automobiles, trains, and high-voltage power transmission. Those high voltage power devices usually are coated with polyimide which is used to suppress leakage at interface of high voltage power device. The polyimide is required to protect from ionic contamination to the power device interface. We have designed a polyimide precursor structure with high light transparency, alkaline solubility and high thermal stability after cure. A novel negative-tone photo-definable polyimide was formulated with cross linking reagent that can easily decompose during cure and high efficiency photo-initiator. Our novel Negative photo sensitive polyimide (PSPI-1) has a patternable capability up to 16 μm thickness on silicon wafer with 350 μmJ/cm2 exposure dose. Photo patternability of PSPI-1 is better than that of the conventional polyimide. The cured film showed excellent properties as follows: 310 °C glass transition temperature (Tg), 500 °C 5% weight loss temperature, 40% elongation, no short observation during bias-HAST (130 °C. 96%, 100hr, 100V 15/30 °m line & space) and good adhesion to Si and Cu substrates. These results indicated a possibility for this novel PSPI-1 to be applicable for passivating power semiconductor.