Thin-film metallization

R. Hintsche, B. Moller, I. Dransfeld, U. Wollenberger, F. Scheller, and B. Hoffmann, Chip biosensors on thin-film metal-electrodes. Sens. Actuators B. B4, 287-291 (1991). 

Gasgnier, M. (1995) The intricate world of rare erath thin films metals, alloys, intermetallics, chemical compounds. In Handbook on the Physics and Chemistry of Rare Earths, eds. Gschneidner. Jr., K.A. and Eyring, L. (Elsevier, Amsterdam, The Netherlands), Vol. 20, p. 105. 

J. Wollenstein, J.A. Plaza, C. Cane, Y. Min, H. Bottner, and H.L. TuUer A novel single chip thin film metal oxide array . Sensors and Actuators B 93 (2003), 350-355. 

DC techniques Include measurement of DC resistance, determination of polarization behavior, and measurement of polarization resistance. Coating resistance has been correlated with corrosion performance by a number of workers. As svunmarlzed by Leldhelser ( ), the results of several independent investigations suggest that coating resistance below about 10 ohm/cm Is associated with the formation of visible under-film corrosion. Parallel DC resistance measurements on thin film metal substrates have been used to study the deterioration of coated metals the technique successfully detected the effects of water after migration to the coating/metal interface (351. 

Ralls KS, Buhrman RA, Tiberio RC (1989) Fabrication of thin-film metal nanobridges. Appl Phys Lett 55 2459-2461... 

Keywords Atomic layer deposition Thin films Metal alkyl precursors ... 

Film electrodes have been essential components of quartz microbalance studies of stoichiometry of many electrodeposition and dissolution experiments as well as polymer electrode characterization [25]. In the quartz microbalance, changes in mass are detected by measurement of changes in the resonant frequency of a quartz crystal oscillator as the mass adhering to the surface changes. The oscillation is feasible because thin-film metal electrodes (typically gold) applied to opposing faces of a piezoelectric quartz crystal serve both to induce the oscillation and to provide a site for electrochemical reaction. 

Barrier metals, as opposed to alloys like AuGeNi, are employed in many thin film metallization systems to promote adhesion and prevent interdiffusion. Gold is an excellent conductor, however, it has very poor adhesion to both Si and GaAs. Gold also shortens the device lifetime when it diffuses into an active region of the device. For this reason it is used in multilayered structures such as Ta/Pt/Ta/Au (50), W/Au (50) and Cr/Au (51). SIMS, AES and RBS have all been used effectively in studying metal-metal interdiffusion, to extract diffusion coefficients, and to estimate device lifetimes. 

Micro electrode arrays can also be produced by thin film technology and silicon micromachining. Electrochemical analysis using planar thin film metal electrodes as transducer can be done with high performance in vitro [59]. 

M. Gasgnier, The intricate world of rare earth thin films metals, alloys, intermetallics, chemical compounds,... 105... 

An imager having an element packing density of 90% is disclosed in US-A-4104674. Infrared photovoltaic detectors of mercury cadmium telluride are mounted on a silicon substrate. Electrical contacts are made by thin-film metallizations. 

Table 1 Resistivities of Representative Thin Film Metallic Conductors...

W.D. Nix Mechanical properties of thin films. Metall. Trans. 20A 2217-2245 (1989)... 

Nonlinear optical infrared-visible sum frequency generation (IR-vis SFG) is a versatile surface-specific vibrational spectroscopy that meets the requirements mentioned above. SFG provides vibrational spectra of molecules adsorbed on a surface, while the molecules in the gas phase do not produce a signal. Consequently, SFG can be operated in a pressure range from UFIV to ambient conditions and still detects only the adsorbed species. A direct comparison of adsorbate structures under UFIV and elevated pressure is therefore feasible. Furthermore, SFG can be applied to molecules adsorbed on single crystals, thin films, metal foils, and supported nanoparticles (46,116-121) and is thus a promising tool to extend surface science experiments to more realistic conditions. 

EP is an elegant way of controlling alkali concentration at the surface of a working metal catalyst by varying its electric potential. The technique is implemented by depositing porous thin-film metal catalysts on solid electrolyte supports. Noteworthy features of EP systems are as follows ... 

As noted above, EP involves controlling the coverage of an electro-active species, supplied from a solid electrolyte, on the surface of a metal thin-film catalyst electrode with which it is in contact. In our case, the electro-active species is alkali ions and the electrolyte is Na (or K) alumina. A schematic of the experimental arrangement is shown in Figure 1. The thin-film metal catalyst must be both continuous and porous. 

For the formation of a metallic film in addition to thick film silk-screen technique, thin film metallization is another means for the film deposition. Deposition of thin film can be accomplished by either physical or chemical means, and thin film technology has been extensively used in the microelectronics industry. Physical means is basically a vapor deposition, and there are various methods to carry out physical vapor deposition. In general, the process involves the following 1) the planned deposited metal is physically converted into vapor phase and 2) the metallic vapor is transported at reduced pressure and condensed onto the surface of the substrate. Physical vapor deposition includes thermal evaporation, electronic beam assisted evaporation, ion-beam and plasma sputtering method, and others. The physical depositions follow the steps described above. In essence, the metal is converted into molecules in the vapor phase and then condensed onto the substrate. Consequently, the deposition is based on molecules and is uniform and very smooth. 

Fig. 3 Processing steps for the deposition and patterning of a thin film metal structure. (The thicknesses of the metal layers are not proportionally scaled.)...

Fig. 4.1.12 Thin-film metal structures on the steel membrane of Bosch s high-pressure sensor and the equivalent circuit of a Wheatstone bridge [27]...

Here we show an example of applying the EFS method to a non-silicon-based pressure sensor to operate at high pressure ranges. The membrane of many high-pressure sensors (Bosch, WIKA) is manufactured of steel, with thin-film metal resistors as a measurement signal pickup (Fig. 4.1.12). 

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