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This work investigated the thermal stability of tungsten carbide (WC x) films deposited by a sputtering process with a WC target as diffusion barrier layer between Cu and Si. The as-deposited WC x film has a nanocrystalline structure and a low electrical resistivity of around 227 ⍀ cm. Film characterization reveals that the WC x film was able to preserve the integrity of the Cu (2000 Å)/WC x ͑500 Å͒/n-Si structure without formation of Cu 3 Si, up to a 600°C annealing for 30 min. In addition, diode leakage current measurements on the same contact structure, but with a p ϩ n-Si substrate did not show deterioration of electrical characteristics up to a 550°C annealing. As the thickness of the WC x barrier was reduced to 150 Å, the WC x film retained the integrity of diodes up to 500°C without increasing the diode leakage current. The failure of WC x film after high temperature annealing is attributed to the Cu diffusion into the Si substrate through grain boundaries or local defects of the WC x barrier layer, in which some local defects may arise from the formation of W 5 Si 3 .

Aluminum nitride ͑AlN͒ thin films were deposited on silicon wafers and glass substrates by an unbalanced magnetron ͑UBM͒ sputtering system equipped with a pulse dc power supply. Microstructure and chemistry of the AlN-coated specimens were characterized by X-ray diffraction ͑XRD͒, scanning electron microscopy ͑SEM͒, transmission electron microscopy ͑TEM͒, atomic force microscopy ͑AFM͒, and X-ray photoelectron spectroscopy ͑XPS͒. The optical transmission properties of the AlN-coated glass were investigated using an ultraviolet/visible ͑UV/VIS͒ spectrophotometer. It was found that the thin films are polycrystalline and have a hexagonal wurtzite structure with ͑002͒ preferred orientation, as revealed by XRD and TEM. AFM analysis indicates that the surface of the thin films is smooth, with an average roughness R a ϭ 6.464 nm, which is suitable for application in surface acoustic wave devices. XPS analysis gives the chemical composition of the coatings as well as the bonding states of the elements. In addition, the AlN thin films are transparent in the visible region with an average transmittance of 60%.

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