Metal etching

Etch Mechanisms. Most wet etches for the compound semiconductors employ oxidation of the semiconductor followed by dissolution of the oxide. For this reason, many wet etches contain the oxidant hydrogen peroxide, although nitric acid can also be used. One advantage of wet etching over dry is the absence of subsurface damage that is common with dry etching. Metal contacts placed on wet-etched surfaces exhibit more ideal characteristics than dry-etched surfaces. 

Nital. A soln of l-5ml of nitric acid (d 1.42 g/cc) in 100ml of 95% ale, used for etching metals. A nital soln contg about 15% by vol of Grasselli reagent, nitric acid and ethanol, used for etching Bi, decomposed vigorously. Explns were also reported when mtal mixts came in contact with other metals. It is believed that the decompn was caused by the reduction of the nitric acid to oxides, which catalyzed the decompn (Ref 1). 

Type of adhesion diffusion ion etching metallic bond... 

Etching- metal and oxide etch equipment are used to remove excess parts of the deposited film. High density plasma sources... 

Figure 3.13 Three methods of chemically etching metal tips for STM. In (a) the current cut-off is manually or electronically triggered when the end of the etched wire falls the finite time delay inherent in this approach results in a blunting of the final tip as etching continues after separation, (b) This shows an adaptation in which the etching current is automatically cut off when the lower portion of the wire drops - it is the lower portion that is used as an STM tip. (c) This shows an improved design in which the etching current is fed to the lower portion of the tungsten wire through an electrolyte held in a conductive beaker. In this case the upper portion of the etched wire is kept.

Acetic anhydride, Organic materials, Transition metals Hikita, T. et al., J. Chem. Soc. Japan, Ind. Chem. Sect., 1951, 54, 253-255 The stability ranges of mixtures of the acid, anhydride and organic materials (ethanol, gelatine) used in electropolishing were studied. Presence of transition metals (chromium, iron, nickel) increases the possibility of explosion. (This is why such mixtures must not be stored after use for etching metals.)... 

The Photopolymer Plate, a water developable photopolymer relief printing master plate made by modification of polyvinyl alcohol with urea group oligomer having a functional polyvinyl base, for making paper mold and matrix for printing master plates, has characteristics which are very close to those of the conventionally etched metal relief printing plates and has some superior points to them. 

As a result of ion bombardment effects and of their ability to reduce native oxides chemically, chlorocarbon or fluorocarbon gases, rather than pure halogens, are typically used to etch metal films (Table IV). 

Fig. 7.7. The effect of tip geometry, (a) The end of a typical etched metal tip. (b) The end of a typical cleaved or cutout tip.

Fig. 5. Effect of outdoor weathering on the strength of aluminum alloy/epoxy-polyamide joints (chromic-sulfuric acid-etch metal surface pretreat-ment)61 (Reprinted from Ref. 61, p. 194, by courtesy of Gordon and Breach...

The composite film grows on the grounded electrode when the sputter-etched metal and free radicals reach the substrate surface. The final metal concentration depends upon the rate at which the two components are generated, and this can be controlled by two means ... 

Provides an alternative means of patterning metal, eliminating the need to plasma etch, difficult to etch metals and alloys... 

So far, two types of metallic tips have been typically reported. One is a metal-coated cantilever and the other is etched metallic wire, each of which is used in a suitable combination with the feedback scheme of tip-sample distance control (see Sect. 4.3). The metal-coated cantilever is fabricated conveniently from a commercially available silicon (Si) or silicon nitride (SisN4) cantilever of AFM by depositing thin metallic film onto the probe surface (Fig. 16.5a) [31-33]. Metal with >99.999% purity is thermally evaporated under vacuum condition and deposited onto the probe surface slowly with a rate of less than 1 A/s in order not to damage the tip apex. The deposition thickness is typically several tens of nanometers. A small diameter of several tens of nanometers at the tip is easily obtained. 

Lithography is a method of printing an image by applying patterned layers of color to paper with a series of etched metal or stone plates. This is the process used to print many newspapers and multi-colored lithographs. It is also the general name for the techniques used to fabricate integrated circuits (ICs). 

The Deep etch plates, on the other hand, are usually etched metal plates using a negatively working photoresist and an etching lacquer. In the Industry the Deep etch plates have found wider usage In view of their mechanical stability towards printing more copies. 

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