Metal Patterning

Metal layers have been deposited on microchip substrates. The metal layer was either used as an etch mask in micromachining, or used for detection (e.g., as metal electrodes for electrochemical detection). Various metals have been used as the overlayer and adhesion layer, as summarized in Table 2.10. 

As an etch mask, Cr/Au was usually employed in which Cr was used as an adhesion-promotion underlayer. In some cases, only Cr was used as the etch mask, mainly on quartz [150,263,264]. In addition, a thick Au film (200 nm) was used as an etch mask to reduce the number of pinholes [108], 

To ensure sufficient adhesion of photoresist on the Au/Cr etch mask on a glass wafer, an adhesion layer of hexamethyldisilazane was coated [265], 

As metal electrodes, various combinations, such as Cr/Au, Ti/Au, Au only, Pt/Cr, and Pt/Ti, have been used. A thin 10-nm Au layer was sometimes used because it was transparent to the visible wavelength (abs 0.2-0.3) [133, 363]. 

To fabricate an array of 1000 non-intersecting Au electrodes on glass, multilayer lithography was used, and Si3N4 was used as the insulating layer [266]. 

---

Foundry Resins. In the foundry industry, phenoHc resins are used as the binder for sand in the manufacture of sheU molds and cores. The two mating halves are joined by clamps or a bonding agent to form a sheU mold into which the molten metal is poured for castings. The sheU is formed by depositing a resin—sand mix on a hot metal pattern plate. After a certain period the pattern is inverted and the excess resin sand is removed. The sand particles are bonded by an oven cure, and the sheU is ejected from the pattern plate. 

Aluminum metallization in combination with tantalum thin films is used for manufacturing thin-film capacitors built into the metallization pattern.340... 

Lee, K. J. Tosser, K. A. Nuzzo, R. G. 2005. Fabrication of stable metallic patterns embedded in poly(dimethylsiloxane) and model applications in non-planar electronic and lab-on-a-chip device patterning. Adv. Funct. Mater. 15 557-566. 

This paper presents some trends for heavy metal patterns in rice-soil systems on a regional scale in Zhejiang province. The major findings are summarized below ... 

Photo-resist technology is widely used for imaging processes in such applications in electronics. If it is wished to produce a metallic pattern of connections between many electronic components (resistors, capacitors, integrated circuits, etc.), this can be done by the selective etching of a thin copper plate deposited on an insulating base. The copper layer is protected by a resist which is a polymer, deposited in such a way that it prevents the attack of the metal by an etching solution which will solubilize only the unprotected, exposed copper (Figure 6.8). 

Figure 7. Metallization pattern for the top layer of a 2.25 by 2.25 in. (5.1 by 5.1 cm) multichip package, with chip footprints, I/O pads, and other surface...

A final alternative for metal patterning is the use of lasers to selectively and accurately etch small metal areas. Lasers are routinely used to trim thin-film resistors (126) they may also be used to repair defects or etch conductor lines by direct ablation in an inert atmosphere (127,129) or by laser-initiated etching in a reactive gas or liquid (128). 

A set of metal pattern plates is heated to 200°C-280°C and coated with a silicone release agent. 

Dry sand, precoated with a phenolic novolac-hexamethylenete-tramine (hexa) formulation, is dropped upon the pattern. After about 15 s-30 s, the mold is turned over (180°C), leaving a shell of several millimeters of sand adhered to the metal pattern. The rest of the sand that falls upon mold inversion is supplemented with fresh coated sand and used in the following cycle. 

The relatively low rate of false assignments (8.3%) compared with the error of a randomly correct reclassification (72.4%) confirms the cluster analytical hypothesis of four partial areas of the test field in which heavy metal pattern differed detectably. 

The application of different multivariate statistical methods enables clarification of the changes of the heavy metal pattern within the test area examined here. A multivariate change of the heavy metal content of the test field from the upper left to the lower right part of the area can be demonstrated in the example investigated. 

The extent of metal complexation for a given set of solution conditions varies widely among metals of interest in aquatic systems, and chemists have sought for many years to develop predictive relationships and a rational basis for understanding metal-to-metal patterns of complexation. Three approaches have been widely used ... 

For many years, nearly all the substrate materials used in the electronics industry were ceramics produced by tape casting (Mistier, 2000). These substrates consist of multiple layers of tape-cast material acting as the insulative carrier, with layers of metal deposited by sputtering, CVD, or evaporation processes. Holes punched into the tapes fill with metal and act as vias or pathways between layers when the tapes are stacked. Stacked layers of tape-cast blanks are laminated together and then sintered to produce a monolithic substrate. This process is detailed in many handbooks on electronics packaging (e g., Harper, 2000). One of the prime benefits is that the layers of the final part can be different different hole patterns, different metallization patterns, even different dimensions on each layer. 

The amorphous Beilby layer (as it is often called) has properties markedly different from the rest of the solid. It is much harder, and is usually more soluble and electrolytically more anodic, a fact of considerable importance in the corrosion of metals, as it is often found that corrosion starts at those points (such as the neighbourhood of a punched hole) where some degree of surface flow, or damage to the crystalline structure, has taken place in the metal. It has, apparently, powers of dissolving other metals, not possessed by a crystalline surface. Thus Finch, Quarrell, and Roebuck1 found that if small amounts of metals were deposited by condensation from vapour on to a polished surface of another metal, patterns indicative of the crystalline structure of the deposited metal were obtained temporarily, but disappeared after a few minutes or even seconds. Permanent patterns of zinc on copper could only be obtained by very many successive depositions. If, however, metals were similarly deposited on crystalline surfaces of other metals, one deposition was always sufficient to give the pattern of the deposited metal. 

Different foundry casting techniques are used. Included are plastic-based binders mixed with sand. Various types of molds and cores are produced that include no-bake or cold-box, hot-box, shell, and oven-cured. Usual binders are phenolic, furan, and thermoset polyester. There is the foundry shell casting, also called dry-mix casting. It is a type of process used in the foundry industry, in which a mixture of sand and plastic (phenolic, thermoset polyester, etc.) is placed on to a preheated metal pattern (producing half a mold) causing the plastic to flow and build a thin shell over the pattern. Liquid plastic pre-coated sand is also used. After a short cure time at high temperature, the mold is stripped from its pattern and combined with a similar half produced by the same technique. Finished mold is then ready to receive the molten metal. Blowing a liquid plastic/sand mix in a core-box also produces shell molds. 

A direct experimental measurement of the surface plasmons bands of the gold nanoclusters was not straightforward, since the metallic patterns were quite small and stuck onto an opaque substrate (SiOz). Therefore, we performed theoretical calculations in order to infer the spectral features of the SPs used in our MEF experiments. The absor[ on spectra of gold triangular prisms and cylinders with thicknesses of 35 nm (according to the dimensions of the fabricated patterns) were calculated by using the Discrete dipole approximation (DDA). Further details on the method are ven in references [52-57]. 

---