Pt embedded ohmic contacts to n+-GaAs (AuGe-800 Å/ Ni-150 Å/Pt-200 Å/Au-500 Å and AuGe-800 Å/Pt-200 Å/Ni-150 Å/Au-500 Å/n+-GaAs) have been developed for the advanced discrete devices and MMIC (monolithic microwave integrated circuit) applications. The specific contact resistance investigated by Transmission Line Method is 1x10-6 Ω cm2. Ohmic contact reliability investigated by thermal storage test at 300 °C under N2 ambient demonstrated nearly the same contact characteristics after 3000 hours. In both systems, X-ray diffraction results and Auger depth profiles show that the good ohmic contact is related to the formation of Au7Ga2, PtAs2, and Ni19Gen12 phases. AuGa compound enhances the creation of Ga vacancies, allowing incorporation of Ge into Ga sites, and PtAs compound is piled up in the middle of AuGa layer to suppress As outdifrusion from GaAs substrate. TEM cross-sectional view indicates that metal/n+-GaAs reaction layer is ∼ 1200 Å beneath GaAs. Surface and interface are very smooth and abrupt in comparison to conventional AuGe/Ni/Au contact.

A dynamic Monte-Carlo simulation (MCS) program, containing not only collisional mixing but also sputtering effects, has been used to elucidate the dynamic mixing processes and the atomic transport of constituents in Al-Pd bilayer systems. MCS results reveal that the preferential inward displacement of the top layer element dominates, and that there is an enhancement of the inward displacement when the heavier element is in the top layer. The inward displacement is controlled by both of an anisotropic and isotropic atomic transport. The anisotropic term is caused by the primary recoil of atoms, which has a characteristic of φ(ion dose) dependence, and the isotropic term is associated with the random cascade motion, which has a dependence. However the outward displacement is governed by only the isotropic motion, thus the inward displacement always dominates over the outward motion, which leads to a preferential displacement of top layer element to the bottom layer.

Ion beam mixing of a Pd/Cu bilayer is studied using irradiation with 80 keV Ar+ ions at room temperature. RBS analysis shows that intermixing has occurred across the Pd/Cu interface, and that the mixing amount increases with increasing ion dose, which agrees well with a model for radiation enhanced diffusion. It is found that the Cu3Pd phase grows in a layer-by-layer manner.

Polyimide thin films are deposited by the ionized cluster beam deposition( ICBD ) technique. Polymerization and crystallization of polyimide were investigated using TEN, IR, and the electronic structure of the polyimide film was investigated using XPS. Films deposited at optimum ion acceleration voltage showed strong preferential crystal orientation. Crystalline polyimide film was obtained at ion acceleration voltage of 700 V.