A novel stack structure to improve the degradation of W-polycide gated MOS device with undoped a-Si/heavily-doped poly-Si multilayer

An original structure with undoped amorphous silicon (a-Si)/heavily-doped polysilicon stacked layers is reported. This structure can help to prevent the deterioration of gate oxide caused by fluorine ions in conventional tungsten-polycide (W-polycide) gated MOS devices. The relationship between the thickness of the stacked a-Si layer and the quality of the gate oxide is also investigated. With this W-silicide/a-Si/polysilicon stack structure, a lower sheet resistance of the W-polycide can also be obtained.