A Fully Integrated Silicon-Based 40-V Thermal Ink Jet IC

A fully-integrated silicon-based thermal ink jet printhead which produces high speed, laser-quality printing at 300 spots per inch resolution is described. Monolithic integration of the 5-V logic circuitry, 13-V predriver circuitry, 40-V MOSFETs, and 192 n⁺ polysilicon heater elements requires multiple process and device design trade-offs. The TIJ printhead is customer replaceable and must be protected from far greater static discharges than normal VLSI circuits. Design issues and failure mechanisms of the power MOSFETs and ESD protection devices are discussed. Two-dimensional simulations which include parasitic bipolar action and lattice heating illustrate the design concepts. Electrical characteristics of the 40-V power MOSFETs and 16-kV ESD protection devices are presented.