Sputtered tungsten gates for AMLCDs

A comparison between aluminum and tungsten MOS capacitors has been performed. The electrical characterization of the capacitors was carried out using HFCV techniques to extract the flat band voltage, fixed charge, and density of interface states. Breakdown measurements were also taken. The data shows that the breakdown voltages and density of interface states are similar for the tungsten and aluminum capacitors. The tungsten capacitors contained twice as much fixed charge. This difference in fixed charge amounts to around a half a volt change in threshold voltage for oxide thicknesses near 1000 Å. This is not significant because it is offset by the difference in work functions between aluminum and tungsten