Metal oxides hydrofluoric acid etch

The tin oxide thin film was patterned by reactive ion etching (RIE) using either SiCl or 1% H2 in N2 as the etch gas. The polysilicon contact holes were opened by wet-chemical etching in buffered hydrofluoric acid (BHF). A double-layer metallization (Cr -50 nm plus A1 -1 pm) was done by electron beam evaporation to form the electrical interconnection (Figure 1c). 

Hydrofluoric acid — (HF) A solution of hydrogen fluoride in water. The pure hydrogen fluoride is characterized by Mw of 20.0063 gmol-1 m.p. -83.55 °C (1 atm) b.p. 19.5 °C (latm). When concentrated, this colorless fuming liquid is extremely corrosive and can dissolve almost all inorganic oxides such as silicate compounds or oxides of metals like stainless steel, aluminum, and uranium however, it can be stored in casted iron bottles because a corrosion-resistant iron fluoride layer protects the metal. It is used for several purposes such as the preparation of titanium oxide nano tube arrays [i], silicon nanoparticles [ii] and electrochemical etching of silicon [iii], electrochemical deposition of lithium [iv], etc. 

Like growth reactions, corrosion at surfaces involves a change in surface composition however, it is typically associated with a deleterious change. Corrosion reactions can be separated into two classes those involving the removal of material from the solid and those involving the formation of a surface reaction layer. In the first type of reaction, gas-or solution-phase species react with the surface to produce volatile or soluble products as in the etching of silicon by hydrofluoric acid. The second type of reaction involves the reaction of surface atoms to form a new compound which remains on the surface. The oxidation of many metals is considered a corrosion reaction of this type. 

Another application area for ion chromatography is the analysis of etching solutions [150] (i.e., mixtures of different acids), with which metal oxides and other impurities can be removed from metal surfaces. The choice of adds depends on the type of materials to be etched. While a mixture of hydrofluoric acid, nitric acid, and acetic acid etches silicon dioxide without affecting elemental silicon itself, mixtures of orthophosphoric acid, acetic add, and nitric acid are... 

Makrides et al (1967) patented a H2-extraction membrane where refractory metals, such as Ta, Nb and V, were coated with Pd to facilitate H2 ingress and egress and to prevent oxidation of the refractory metal surfaces. They started with commercially available foils. After being etched electrolytically in hydrofluoric acid and washed with acetone, the wet foils were placed in a vacuum chamber where they were further dried by evacuation. After... 

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