PHOTOCHEMICAL DRY-ETCHING OF DOPED AND UNDOPED SILICON-OXIDES

The photochemical dry etching of doped and undoped silicon oxides with ClF3 and F-2 gas has been investigated. Etching rates of several hund red angstroms per minute have been achieved with bulk substrate temper atures below 300 degrees C. Borophosphosilicate glass-to-thermal oxide etching rate selectivity is near 1-to-1 over a wide range of process conditions; The addition of Cl-2 gas is found to significantly reduce the etching rates of both doped and undoped silicon oxide under these conditions. The photochemical dry cleaning of a 10 to 20 A chemical ox ide layer from trench and via bottoms is discussed.