Investigation of the interfacial reaction between metal and fluorine-contained polyimides J. Vac. Sci. Technol. A 23, 862 (2005); 10.1116/1.1868632
Failure mechanism of Ta diffusion barrier between Cu and SiThin films of tantalum, a potential diffusion barrier, were deposited on xerogel films. The structures were annealed at different temperatures and in different ambient environments and analyzed using Rutherford backscattering spectrometry ͑RBS͒, optical microscopy, and the Scotch™ tape test, in order to assess the extent of interaction with the xerogel film. When annealed in nitrogen with at most trace amounts of oxygen ͑equivalent to 10 Ϫ7 -10 Ϫ6 Torr vacuum͒, RBS analysis for Ta does not show diffusion of this metal through the xerogel when annealed up to 450°C. However, the presence of larger concentrations of oxygen in the annealing environment was found to cause oxidation of Ta thin films, and this leads to Ta film buckling and diffusion-like RBS spectra. Ta does not buckle nor diffuse into the xerogel film at temperatures up to 640°C when the metal is capped with a Si 3 N 4 layer. Analysis of the samples by RBS microbeam shows that the low energy Ta tail originates from only a portion of the sample surface, the shape of which resembles Ta buckles. RBS spectra collected from other parts of the samples show no Ta diffusion into xerogel. Adhesion of Ta to porous xerogel is reduced compared to SiO 2 , due to the reduced contact area at the interface between the materials.
Thin barium titanate films, 0.5–8 μm thick, are obtained from a single-crystal bulk sample using ion slicing. The process, based on ion implantation and anodic bonding, separates thin films having areas of ∼1×1 cm2, from bulk crystals. The quality of the film is characterized by measurement of surface roughness and dielectric properties. The film permittivity retains its single-crystal value.
The dielectric response has been studied in 10-m-thick, single-crystal potassium tantalate films formed by crystal ion slicing. Scanning microwave microscopy shows that the implanted, pre-etched samples exhibit a bulk-like permittivity and low-loss tangent ͑0.0009͒ at 1.7 GHz. The separated free-standing films have somewhat higher loss tangents due to residual-ion-induced stress. Selective relaxation of this stress by etching or annealing reduces the dielectric loss.
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