Plasma-Radiation-Induced Interface States in Metal-Nitride-Oxide-Silicon Structure of Charge-Coupled Device Image Sensor and Their Reduction Using Pulse-Time-Modulated Plasma

Abstract

We found that ultraviolet (UV) light from helium discharge plasma and a halogen lamp clearly induce SiO2-Si interface states in a metal-silicon-nitride-oxide-silicon (MNOS) structure. A dark current originating in the interface states of charge-coupled-device (CCD) image sensors also increases by this UV irradiation. Pulse-time-modulated (TM) plasma suppresses the interface states, resulting in the CCD dark current, by decreasing the UV light. On the other hand, results of Capacitance-Voltage (CV) measurement did not show the difference between UV irradiation and no irradiation. This indicates that fixed charges in the SiO2 cannot be generated by the UV lights. Using optical filters, we revealed that a photon energy of 3.90 eV (318 nm) to 4.96 eV (250 nm) causes an increase in the interface states.