METHOD FOR REDUCTION IN SURFACE GENERATION CURRENT IN POLYCRYSTALLINE-SILICON-GATE METAL-OXIDE-SEMICONDUCTOR DEVICES

Generation current from interface states at the Si/SiO2 interface is a dominant noise source in metal-oxide-semiconductor type solid-state imagers. A simple method to reduce the interface state density of the solid-state imagers is described. The method involves annealing at 450-degrees-C in the presence of an unpatterned aluminum film over the layer of passivation oxide of a completed device. In comparing this method to the conventional process of annealing with patterned aluminum, this method results in an order of magnitude reduction in surface generation current. It is believed that Al reacts with trace water in the chemical-vapor-deposition oxide and generates active hydrogen. Hydrogen diffuses through the oxide and polycrystalline-silicon gate to the Si/SiO2 interface and passivates the interface states.