Nickel-Chromium+Gold metallization for MOS devices

A nickel-chromium+gold (NiCr+Au) metallization system, consisting of a vacuum deposited 150 Å layer of NiCr underneath a 3000 Å layer of Au, has been used in the fabrication of p-channel enhancement mode transistors and integrated circuits. The devices exhibit both low VTH(-2.3 volts) and small shifts in threshold voltage (-.16 volts) due to ionic drift resulting from bias-temperature stress. These results for NiCr+Au devices which do not require passivation or heat treat are better than results obtained with similar devices which were gate oxide passivated, metallized with Al, and heat treated.