Highly reliable 1200-V p-type MOSFET for level-shift circuit used in driver IC

We developed a highly reliable 1200-V p-type MOSFET for level-shift circuits. A new phenomenon, in which the leakage current increases and decreases irregularly in AC half-wave bias near avalanche voltage and the blocking voltage decreases with the long-term durability, was observed from test results of developed prototype driver ICs at an AC half-wave voltage of 1380 V. We analyzed this phenomenon through device simulation. The reason of this phenomenon was that the avalanche point of a prototype 1200-V p-type MOSFET shifted and the leakage current changed in one cycle of the AC half-wave. The device structure and process were improved on the basis of this analysis, resulting in a highly reliable p-type MOSFET.