Highly Selective Etching of SiO2 over Si3N4 and Si in Capacitively Coupled Plasma Employing C5HF7 Gas

Abstract

In a dual-frequency-excited parallel plate capacitively coupled plasma employing a heptafluoro-cyclo-pentene (C5HF7) gas with addition of O2 and dilution in Ar gas, highly selective etching of SiO2 at selectivities of 40 against Si3N4 and 57 against polycrystalline Si was realized. Gas phase fluorocarbon species containing H atoms such as CxHFy (x>2) played key roles in the selective deposition of thick hydrofluorocarbon films that covered the Si3N4 and polycrystalline silicon (poly-Si) surfaces and in the selective etching of SiO2 over the photoresist, SiN, and Si.