TECHNOLOGY FOCUS - ELECTRONICS - Preferred composition: The composition has a GWP of less than or equal to 1000 and the etchant compound has a formula, F-CO-((CR1R2)m-CO)n-Fm = 0, 1, 2, or 3;R1 and R2 = FEspecially preferred is an etchant selected from F-CO-CO-F and F-CO-(CF2)m-CO-F. The composition is preferably free of fluorocarbon compounds with a GWP greater than 5000 and sulphur-based compounds with perfluorinated side chains and with a GWP greater than 1500. The etchant compound (C) preferably etches Si3N4 at an etch rate = 250-300 angstroms/minute at a plasma power = 350 watts at 2.45 GHz, a pressure = 1 mTorr and a DC bias = 41 volts.Preferred modifier: The composition may also comprise an etchant modifier selected from O2, H2, N2, 1-4 C perfluorocarbons and 1-5 C hydrofluorocarbons. Especially preferred are pentafluoropropane, hexafluoropropane, tetrafluoroethane and pentafluoroethane and combinations of these. The etchant modifier may also be a different compound from the etchant compound and is compound (C) except that n = 0 or 1; and at least one of R1, R2 and R4 to R7 = H or is hydrogen containing. Alternatively the second constituent is a carrier gas which imparts volatility to the etching composition and may be a high ionization gas which enhances the rate of etching and is especially He, Ar or their combinations.Preferred material: The material (MT) to be etched is preferably selected from the group consisting of: dielectrics selected from the groups consisting of carbides, borides and silicides of metals or semi-metals; insulators selected from the group consisting of oxides, nitrides of metals or semi-metals, boronphosphorous silicate glass, and fluorosilicate glass; III-V semiconductor compounds; elemental materials selected from the group consisting of silicon, polycrystalline silicon, tungsten, titanium, vanadium, germanium, and silicon-germanium and combinations of two or more of these. The material especially comprises one or more layers of a semiconductor. EXAMPLE - Oxalyl fluoride (F-CO-CO-F) was used to etch at a DC bias = 41 volts, a pressure = 1 mTorr and a power = 350 watts. Etch rates (angstroms/min) of various materials was as follows: single crystal silicon = 206.4; polysilicon = 220.6; silicon dioxide = 315.8 and silicon nitride = 269.