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.