Metallising

Most xanthene dyes are classified as basic dyes by their method of appHcation acid dyes can be produced by introduction of sulfonic acid groups. The fluoresceins, which contain carboxy and hydroxy substituents, are also acid dyes for coloration of silk. Some of the fluoresceins in which the carboxy group has been esterified, are soluble in alcohol or other organic solvents and can be classified as solvent dyes. Mordant dyes can be produced by introducing o-dihydroxy or sahcyhc acid groups (2), which when metallised can have very good lightfastness. 

Molybdenum hexafluoride is used in the manufacture of thin films (qv) for large-scale integrated circuits (qv) commonly known as LSIC systems (3,4), in the manufacture of metallised ceramics (see MetaL-MATRIX COMPOSITES) (5), and chemical vapor deposition of molybdenum and molybdenum—tungsten alloys (see Molybdenumand molybdenum alloys) (6,7). The latter process involves the reduction of gaseous metal fluorides by hydrogen at elevated temperatures to produce metals or their alloys such as molybdenum—tungsten, molybdenum—tungsten—rhenium, or molybdenum—rhenium alloys. 

OPP producers have expanded the core, creating a foam stmcture with lower density, greater opacity, and a stiffer, more paper-Hke feel. Vacuum metallisation increases opacity and water-vapor barrier properties. 

Poly(methyl methacrylate). PMMA offers distinct advantages over BPA-PC with respect to significandy lower birefringence, higher modulus, and lower costs, but has not been successhil as a material for audio CDs and CD-ROM as well as a substrate material for WORM and EOD disks because of its high water absorption (which makes it prone to warp) and its unsuitabiUty for metallising, and less so because of its low resistance to... 

Dopant species can be codeposited with the Si02 by introducing small amounts of the dopants in hydride or haUde form. P-doped Si02, called P-glass, functions as an insulator between polysiUcon gates and the top metallisation layer of ICs. It is also used as a final passivation layer over devices, and as agettering source (17). 

The blanket deposition is then sputter etched through a resist to pattern the metallisation. Selective deposition of W, under development, would deposit metal only in desired areas, and would reduce process steps and costs. 

Copper is an attractive metallisation element because of its high conductivity. It has been added to Al in low concentrations (AlSi(l%)—Cu(0.5%)) to improve conductive priorities. Selective, low temperature copper CVD processing, using copper(I) P-diketonate compounds, has been carried out (23). 

Impurities that can negatively affect the physical and electrical properties of the metallisation layer can originate from several sources, particularly the deposition source and the gaseous environment. Impurities stemming from the source bombard the surface of the growing film and get trapped in the metal layer. 

Finally, the metallisation layer usually requires patterning, which can be done by reactive ion etching (RIE) or back-sputtering. The two processes are similar. In both techniques accelerated ions hit the substrate and forcibly detach atoms or molecules from the surface. RIE uses reactive gases such as chlorine, Cl or trichlorofluoromethane [75-69-4] CCl E. Inert gases such as argon or neon are used in back-sputtering. 

Step 9. Si02 is blanket deposited over the substrate. The resist (mask 3) that has openings over the Si02 is deposited and patterned. The exposed Si02 is etched down to the source, drain, and gate layers, creating contact windows for metallisation. 

Step 10. The system is metallised, first with a tungsten layer, then with Al. The resist is appHed and patterned (mask 4), and unwanted metal is etched away. 

Fig. 9. Fabrication sequence for an oxide-isolated -weU CMOS process, where is boron and X is arsenic. See text, (a) Formation of blanket pod oxide and Si N layer resist patterning (mask 1) ion implantation of channel stoppers (chanstop) (steps 1—3). (b) Growth of isolation field oxide removal of resist, Si N, and pod oxide growth of thin (<200 nm) Si02 gate oxide layer (steps 4—6). (c) Deposition and patterning of polysihcon gate formation of -source and drain (steps 7,8). (d) Deposition of thick Si02 blanket layer etch to form contact windows down to source, drain, and gate (step 9). (e) Metallisation of contact windows with W blanket deposition of Al patterning of metal (steps 10,11). The deposition of intermetal dielectric or final...

From this relationship it can be seen that a reduction level of 95% compares with a metallisation level of 92.5%. A reduction level of 33.33% or less has a metallisation level of 0%. DRI normally has at least 90% reduction or 85% metallisation. Processes producing soHd, partially reduced iron, ie, <90% reduced or <85% metallised, are classified as prereduction processes. The partially reduced product, called prereduced iron, is not acceptable for steelmaking but can be used as a feed for iron smelting. 

Flame spray metallising is widely used for the protection of metal against corrosion, especially for in situ protection of stmctural members. The principal metal used for spraying of plastics is sine. Aluminum and copper are also used. If the distance from the part is too great, the zinc solidifies before it touches the part and adhesion is extremely poor. If the molten zinc oxidizes, conductivity and adhesion are poor. If the distance is too short, the zinc is too hot and the plastic warps or degrades. These coatings are not as dense as electrically deposited coatings because of numerous pores, oxide inclusions, and discontinuities where particles have incompletely coalesced. 

R. Suchentmnch, Metallisation of Plastics, Finishing Pubhcations Ltd., Herts, U.K., 1993. 

Advanced Metallisation for UESI Applications, Oct. 20—22, 1992 Tempe, Aris, Materials Research Society, Pittsburgh, Pa., 1993. 

S. P. Murarka, Metallisation Theory and Practice for UESI and UESI, Butterworth-Heineman, Boston, Mass., 1993. 

Plating and Suface Finishing Semiconductor International, and Metal Finishing provide some of the best information on innovative metallising methods. 

Naphthalenediol. 1,5-Dihydroxynaphthalene or Asurol is a colorless material which darkens on exposure to air. It is manufactured by the fusion of disodium 1,5-naphthalenedisulfonate with sodium hydroxide at ca 320°C in high yield. 1,5-Naphthalenediol is an important coupling component, giving ortho-a2o dyes which form complexes with chromium. The metallised dyes produce fast black shades on wool. 1,5-Naphthalenediol can be aminated with ammonia under pressure to 1,5-naphthalenediamine. 

Etch Profiles. The final profile of a wet etch can be strongly influenced by the crystalline orientation of the semiconductor sample. Many wet etches have different etch rates for various exposed crystal planes. In contrast, several etches are available for specific materials which show Httle dependence on the crystal plane, resulting in a nearly perfect isotropic profile. The different profiles that can be achieved in GaAs etching, as well as InP-based materials, have been discussed (130—132). Similar behavior can be expected for other crystalline semiconductors. It can be important to control the etch profile if a subsequent metallisation step has to pass over the etched step. For reflable metal step coverage it is desirable to have a sloped etched step or at worst a vertical profile. If the profile is re-entrant (concave) then it is possible to have a break in the metal film, causing an open defect. 

Nylon is similar ia its general chemical stmcture to the natural fiber wool, and therefore all the previously described processes for wool are appHcable to dyeiag nylon with acid, metallised, and other dyes. There are, however, significant differences. Nylon is synthetic, it has defined chemical stmcture depending on the manufactufing process, and it is hydrophobic (see Fibers, POLYAMIDES). 

Many red dyes are based on H-acid [90-20-0] (11), eg, Reactive Reds 2, 24, and 218. Others are substituted phenyl and naphthyl or metallised systems (7) (Table 2). Violet dyes are also metallised monoaso dyes (7). 

Blue dyes are derived from anthraquiaone, phthalocyanine, or metallised formasan (7) (see Dyes, anthraquinone) (Figs. 1 and 2). There are also oxasiae and thiasine dyes reported (13) (see AziNEDYEs) (Fig. 2). 

Fig 19 11 Joining methods for ceramics (a) glaze bonding, (b) diffusion bonding, (c) metallisation plus brazing. In addition, ceramics can be clamped, and can be joined with adhesives. 

In terms of processing there is no need for pre-drying PCHE granules, a standard extruder screw as used for polycarbonate may be used and discs are said to release well from the mould. Question marks remain on the oxidative stability of the polymer and on the quality of adhesion of the reflective layer but Dow claim that metallising is possible. 

The principal uses of polyfethylene terephthalate) film are electrical, particularly in capacitors, as slot liners for motors and for recording tape. Its high strength and dimensional stability have led to a number of drawing office applications. The film is also a useful packaging material whilst metallised products have a number of uses as a decorative material. 

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