Abstract: Ionic liquids having melting points below about 100 C formed by reaction of a heterocyclic amine with about 2.8 and about 3.2 moles of anhydrous hydrogen fluoride per mole of amine nitrogen. Electrochemical devices having non-aqueous electrolytes containing the ionic liquids are also disclosed, as well as silicon oxide etching compositions containing the ionic liquids and etching methods in which silicon oxides are selectively removed by the etching compositions in the presence of aluminum.

Abstract: High contrast, sensitivity and bath life is obtainable by the addition of inorganic salts, preferably a carbonate, to an aqueous alkali metal base containing a carboxylated surfactant. The preferred alkali metal bases are potassium hydroxide or sodium hydroxide. The carboxylated surfactants contemplated by the invention are those encompassed with the formula:R--O--(CH.sub.2 H.sub.4 O).sub.n --CH.sub.2 --COOXwherein R is a hydrocarbon radical of 6-18 carbon atoms alkyl radical, n has a value of 1-24 and X is a cation such as K.sup.+, Na.sup.+, or H.sup.+. The gain in sensitivity with the incorporation of an inorganic compound furnishing ions, typically an inorganic salt, to the developer with the carboxylated surfactant compared to the sensitivity obtained with developers with carboxylated surfactant and inorganic salts omitted was typically two fold and greater without a corresponding film loss. Examples of salts are those that contain the anions SO.sub.4.sup.2-, CO.sub.3.sup.2-, Cl.sup.-, PO.sub.4.sup.