Physics of palladium metal-oxide-semiconductor devices

Abstract: This thesis Palladium gate metal-oxide-semiconductor (PdMOS) devices are used as hydrogen sensors. It is shown that the sensitivity is only partly due to the change of the effective work function of the Pd gate on hydrogen adsorption. Sodium ion drift experiments have shown that hydrogen-sodium interactions occur in PdMOS devices. Hydrogen ions adsorb in the first atomic layers of the silicon dioxide. This is the origin of an instability problem called hydrogen induced drift (HID). The HID can be avoided by the insertion of another insulating material (alumina, silicon nitride or tantalum pentoxide) between the silicon dioxide and the metal gate.A hydrogen induced deterioration of the Pd gate metal has been observed. Blisters in the gate metal are formed due to a hydrogen induced stress in the film. A solution to this problem has been found.The catalytic properties of palladium and platinum gate metals are compared in different hydrogen/oxygen mixtures. PdMOS devices are superior for detection of low hydrogen concentrations, whereas PtMOS devices are more suitable at higher concentrations. High frequency capacitance-voltage measurements have shown that hydrogen induced oxide surface charging occurs in PdMOS devices. It is concluded that the surface charges are protons