Thin film conductors

For many power systems, hundreds of amperes of current may be flowing through a substrate in a relatively small area. To prevent severe losses in the conductors, the metallization must be very thick and low in resistivity. One approach to this problem is direct bond copper (DBC), which was developed by General Electric in the mid-1970s. Unlike thick-film or thin-film conductors, DBC can be purchased with metal thicknesses up to 0.65 mm (25 mil). Combined with the low resistivity of copper (0.12 mD/n) and a high thermal conductivity substrate such as AIN, this approach creates nearly the ideal substrate for this type of application. 

Ufetime defects - key variables (perhaps acting in combination) RH, temperature, applied voltage across circuit lines, current density through thin-film conductors, thermal gradients, thermal cycles, thermal shock, mechanical stresses, pollutant concentration in the environment, chemically active process residues, oxygen partial pressure. 

Laminated stacks are fired in belt or box furnaces to bum out organic binders and den-sify the ceramic and metallic constituents. Burnout and firing can be accomplished in one continuous operation so that the part does not experience thermal gradients from end to end as temperature is changed. Finished parts may be metallized with either a screen-printed thick film or sputtered and etched thin-film conductor. 

Stripe, conductor (electrical) A thin film conductor line produced using masking or etching techniques. 

Lloyd, J.R. Electromigration in thin film conductors. Semicond. Sci. Technol. 1997, 12, 1177-1185. Cottrell, A.H. An Introduction to Metallurgy E. Arnold London, 1968 402 pp. 

In moist enviromnents, water is present either at the metal interface in the fonn of a thin film (perhaps due to condensation) or as a bulk phase. Figure A3.10.1 schematically illustrates another example of anodic dissolution where a droplet of slightly acidic water (for instance, due to H2SO4) is in contact with an Fe surface in air [4]. Because Fe is a conductor, electrons are available to reduce O2 at the edges of the droplets. 

Sample requirements Solid conductors and insulators typically, <2.5 cm in diameter, and < 1 cm thick, polished flat particles, rough surfaces, and thin films... 

Apart from applications in sensors [21, 22], divalent-ion conductors, e.g., for Mg2+ ions, are of great interest for thin film batteries which may be incorporated into microelectronics as memory backups and into other applications. For these batteries high volumetric specific energy densities rather than high current densities are required, and thin films offer in addition a major decrease in the total ionic resistance. 

Interconnect. Three-dimensional structures require interconnections between the various levels. This is achieved by small, high aspect-ratio holes that provide electrical contact. These holes include the contact fills which connect the semiconductor silicon area of the device to the first-level metal, and the via holes which connect the first level metal to the second and subsequent metal levels (see Fig. 13.1). The interconnect presents a major fabrication challenge since these high-aspect holes, which may be as small as 0.25 im across, must be completely filled with a diffusion barrier material (such as CVD titanium nitride) and a conductor metal such as CVD tungsten. The ability to fill the interconnects is a major factor in selecting a thin-film deposition process. 

CVD is a maj or process in the production of thin films of all three categories of electronic materials semiconductors, conductors, and insulators. In this chapter, the role of CVD in the fabrication of semiconductors is reviewed. The CVD production of insulators, conductors, and diffusion barriers is reviewed in the following chapter. The major semiconductor materials in production or development are silicon, germanium, ni-V and II-VI compounds, silicon carbide, and diamond. 

State-of-the-art TOF-SIMS instruments feature surface sensitivities well below one ppm of a mono layer, mass resolutions well above 10,000, mass accuracies in the ppm range, and lateral and depth resolutions below 100 nm and 1 nm, respectively. They can be applied to a wide variety of materials, all kinds of sample geometries, and to both conductors and insulators without requiring any sample preparation or pretreatment. TOF-SIMS combines high lateral and depth resolution with the extreme sensitivity and variety of information supplied by mass spectrometry (all elements, isotopes, molecules). This combination makes TOF-SIMS a unique technique for surface and thin film analysis, supplying information which is inaccessible by any other surface analytical technique, for example EDX, AES, or XPS. 

The type of conductance exhibited by the oxide and its value are structure sensitive. The oxide is essentially an ionic conductor. One could maintain that it has a relatively high concentration of low-mobility ionic charge carriers. As far as electronic conductance is concerned although pure alumina is an insulator with a band gap of 8 to 9 eV, one has to bear in mind that when it is produced anodically as a thin film adhering firmly to the metal, an entirely different electronic situation may arise [cf. Section V(2)]. 

In an example of the construction of such a device, thin films of these materials are deposited on OTEs that are separated by a layer of a transparent ionic conductor such as KCF3SO3 in polyethylene oxide).125 The films can be colored simultaneously (giving deep blue) when a sufficient voltage is applied between them such that the WO3 electrode is the cathode and the PB electrode the anode. Conversely, the colored films can be bleached to transparency when the polarity is reversed, returning the ECD to a transparent state. 

Cao, Q. et al. 2006. Highly bendable, transparent thin-film transistors that use carbon-nanotube-based conductors and semiconductors with elastomeric dielectrics. Adv. Mater. 18 304-309. 

The thin film behaves like a free electron conductor. It is proposed that there are sufficient copper ions in the thin film to make it fairly conducting. As the film thickness increases, the conductivity of the film decreases at constant potential and consequently the deposition rate decreases. When the film thickness is above 15 microns there is practically no further deposition of the photopolymer film. 

This definition requires some explanation. (1) By interface we denote those regions of the two adjoining phases whose properties differ significantly from those of the bulk. These interfacial regions can be quite extended, particularly in those cases where a metal or semiconducting electrode is covered by a thin film. Sometimes the term interphase is used to indicate the spatial extention. (2) It would have been more natural to restrict the definition to the interface between an electronic and an ionic conductor only, and, indeed, this is generally what we mean by the term electrochemical interface. However, the study of the interface between two immiscible electrolyte solutions is so similar that it is natural to include it under the scope of electrochemistry. 

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