A study on the effect of the gate contact geometry and dimensions on ESD failure threshold level of power MOSFET´s

The effect of the gate contact geometry and dimensions on the catastrophic electrostatic discharge (ESD) failure of power MOSFET´s that have ESD protection circuits between their gate and source has been studied. This paper describes the relationship between the ESD failure threshold level and the gate contact width of MOSFET´s. It has been found from numerical analysis that only the area near the gate contact, and not the entire gate, is sensitive to the ESD pulse, because the diffusion of the ESD charge into the inner region is suppressed by the sheet resistance of the gate polycrystalline silicon (poly-Si) film. It is also shown here that widening the gate contact and carefully designing the shape of the gate contact, as well as lowering the gate poly-Si sheet resistance, substantially enhance the ESD failure threshold level of power MOSFET´s because a greater portion of an ESD charge can diffuse into the gate region of the device