Thermal ink jet printheads with power MOS driver devices having enhanced transconductance

摘要

A high voltage MOS transistor, for use in a thermal ink jet printhead, is fabricated with a single, uniformly thick layer of polysilicon that serves as a field plate over the drift region and a gate over the channel region. The fabrication of the drift region and associated drift oxide is performed in a sequence independent of the device channel stop and field oxide fabrication, allowing the drift region to be optimized by varying the thickness of the drift oxide. Using a field plate to increase the breakdown voltage of the device by reducing the concentration of the electric field, the device transconductance is increased by increasing the doping of the drift region without an attendant decrease in breakdown voltage.