X-ray photoelectron spectroscopy analyses of oxide-masked organic polymersetched in high density plasmas using SO2/O-2 gas mixtures

Top surface imaging processes are considered as attractive schemes for futu re lithographic processes. A major issue associated with these schemes is t he dry development step which implies the obtention of anisotropic resist p rofiles. This anisotropy is achieve by adding SO2 to O-2 gas mixtures. In t his work, oxide-masked organic resist features are etched in high density p lasma sources using SO2/O-2 gas mixtures. The chemical constituents present on the tops, sidewalls, and bottoms of the etched features are determined by quasi ira situ x-ray photoelectron spectroscopy (XPS). XPS analyses show that when using SO2/O-2 gas mixtures, a thin passivation layer is formed o n the sidewalls of the polymer features. This layer is mainly formed by sul fur atoms present on the polymer surface in elemental state or bonded to ca rbon atoms. This film is thick enough to minimize the spontaneous etching r eaction of oxygen atoms with the organic resist. Samples are also analyzed after air exposure in order to determine the air-induced modification of th e reactive layers formed during the dry development step. XPS analyses show that the sulfur-based passivation layer formed during the etch process int eract with water moisture to form sulfur-based acids. (C) 1999 American Vac uum Society. [S0734-211X(99)00504-1].