Gold/niobium thin film metallizations for gallium arsenide devices and circuits

As the information age opens, the demand for high performance electronics is increasing exponentially. High-speed communications devices and equipment are at the heart of this expansion. Gallium arsenide field effect transistors are the building blocks for those devices.;GaAs FETs provide operation at speeds more than six times that of conventional silicon devices. There is a need to develop and expand the materials knowledge base in all aspects to the fabrication of III/V semiconductors.;Of particular interest is developing a metallization for gallium arsenide circuits and devices that will provide a high quality diffusion barrier. The metallization must provide adhesion to the GaAs surface. It must be thermally and chemically stable. It must be compatible with the other materials encountered in semiconductor processing and packaging.;A niobium/gold thin film system for first level metallization on GaAs is proposed and examined. Niobium displays good adhesion to other semiconductor substrates such as Si, SiO2, and diamond. It is corrosion resistant. Niobium has the third lowest resistance of the refractory metals. Finally, the melting point of TM = 2467°C suggests that niobium will have high temperature stability and low interdiffusion coefficients.;The kinetics of Nb/Au thin films was examined using sheet resistance measurements, X-Ray diffraction and Auger Electron Spectroscopy depth profiling techniques. The data is analyzed using the Matano method and a technique proposed by Zhang and Wong to take into account the fort-nation of an intermediate intermetallic phase. The relevant diffusion coefficients for two kinetics regimes are presented.;Finally, niobium/gold was used as a Schottky contact on GaAs and subjected to an anneal study. It was found that the series resistance of Schottky diodes decreased with a 1 hour anneal at 250°C to 12.5O, and remained stable for temperatures of 250°C for 672 hours. It was found that the series resistance degraded significantly for anneal conditions that were likely to cause intermetallic formation, increasing to 100O. The result of this work is a set of engineering guidelines for the application of niobium/gold metallizations to gallium arsenide circuits and devices.