Etching procedures

Processing details for the optimized FPL etching procedure, other chromic-sulfuric acid etches and the P2 etch are summarized in Table 1 [2,62J. 

The selectivity of this etching procedure can be expressed quantitatively by a differentiation ratio with respect to one phase ... 

Figure 13. Image of mask produced by exposure of a PATE film followed by appropriate rinsing/etching procedure on copper board.

In the etching procedure, copper concentration is continuously increased by the etching and, to keep the etching efficiency constant and optimal, spent etchant has to be withdrawn and replaced with fresh etchant (replenisher). An alternative would be to remove a part of the copper content from the spent etchant, without changing the other conditions in the solution, in such a way that the barren etching solution can be recycled. This process is called the MECER process [2,25]. 

The art of making sharp tips using electrochemical etching was developed in the 1950s for preparing samples for field ion microscopy (FIM) and field electron spectroscopy (FES). A description of various tip-etching procedures can be found in Section 3.1.2 in the book of Tsong (1990). 

Similar approach has also been taken by Ferain and Legras [133,137,138] and De Pra et al. [139] to produce nanostructured materials based on the template of the membrane with etched pores. Polycarbonate film was also of use as the base membrane of the template, and micro- and nanopores were formed by precise control of the etching procedure. Their most resent report showed the successful formation of ultrasmall pores and electrodeposited materials of which sizes were as much as 20 nm [139]. Another attractive point of these studies is the deposited materials in the etched pores. Electrochemical polymerization of conjugated polymer materials was demonstrated in these studies, and the nanowires based on polypyrrole or polyaniline were formed with a fairly cylindrical shape reflecting the side wall structure of the etched pores. Figure 10 indicates the shape of the polypyrrole microwires with their dimension changes by the limitation of the thickness of the template. 

The system for bonding to enamel was developed by Buonocore in the 1950s [260]. This acid etch procedure requires the preparation of the enamel surface with an acidic solution, usually about 37 % phosphoric acid. The surface then has altered surface tension and altered topography with enamel prismatic tags approximately 25 microns long and 5 microns apart [258,261]. An unfilled, low viscosity resin can be allowed to flow between these tags and then polymerize to form a tight junction with the tooth enamel [262]. 

Chromium [10,39], niobium [42], titanium [13], and 90% titanium/10% tungsten [58] have been used as adhesion layers for platinum deposition. Chemical etching procedures based on H202/ethylenediamine tetraacetic acid (EDTA)/ NH4OH have been described for removal of interfering titanium [13] or tita-nium/tungsten [58] adhesion components from the surface of platinum electrodes. The procedure was shown to be effective for more than 24 h after treatment,... 

Figure 10.18 schematically illustrates the process. It uses elastomeric stamps similar those of pCP. or hard stamps formed using the etching procedures outlined in Fig. 10.10. Depositing a thin layer of solid material on to the raised features of the stamp constitutes the inking step. All of the examples described here use electron beam evaporation of a thin layer of Au (20-50 nm) or a bilayer of Au (20-50 nm)/Ti (2-5 nm).

Fig. 10.14. Potentiodynamic runs of p-Si electrode in 0.5 M H2S04. Illumination by a 50-mW cm-2 Xe lamp. The etching procedures were in HF and HNOg, and from H to L the degree of HF etching increased. (Reprinted from M. Szklarczyk, J. O M. Bockris, V. Brusic, and G. Sparrow, Int. J. Hydrogen Energy, 9 707, Copyright 1984. Reproduced with permission of T.Nejat Veziroglu.)...

For this application, a rough and well-defined surface morphology is necessary. It is achieved by post-deposition wet-chemical etching (see [113] and Chaps. 6 and 8). The film thickness to be deposited is in the order of 1,000 nm and about 300 nm of layer thickness is removed by the wet-chemical etching procedure. 

Approaches for the development of water-resistant surface treatments include application of inhibitors to retard the hydration of oxides or the development of highly crystalline oxides as opposed to more amorphous oxides. Standard chemical etching procedures, which remove surface flaws, also result in improved resistance to high humidity. 

The procedure for the fabrication of the Pt submicroelectrodes is shown in Fig. 3.16 (Slevin etal. 1999). Namely, Step I Seal of Pt microwire (Fig. 3.16a). The Pt microwire with 50 pm diameter was mounted in a glass capillary, which was drawn to a fine point using a pipette puller with 3-5 mm microwire protruded from the tip of glass capillary. Step II Etching Pt microwire (Fig. 3.16b). The protruded Pt wire was electrochemically etched by applying 1.2 V potential between the Pt wire and the counter electrode. The etching procedure was finished when the current decreased to zero. Step III Microwire insulation (Fig. 3.16c). Insulating paint... 

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