Reactive Ion Etched MO/CR Source-Drain Metallization for Amorphous Silicon Thin Film Transistors

ABSTRACTA novel two step reactive ion etch (RIE) process is described for the etching of bilayer Mo/Cr source-drain metallization on hydrogenated amorphous silicon (a-Si:H) inverted-staggered thin film transistors. The Cr acts as an etch stop during Mo etching, and is thin enough (∼3 0 nm) that only a small thickness of underlying a-Si is removed during the Cr etch. The resulting Mo/Cr profile is sloped, compared to the more vertical and somewhat uncontrolled slope that is achieved with Mo wet etch. Very similar transistor behavior was observed for both Mo wet etched and Mo/Cr reactive ion etched source-drain metallization. The major advantage of this process over wet etching of Mo source-drain is improved step coverage of subsequently deposited layers due to the less vertical sidewall slope.