Surface characterization of ion-enhanced implanted photoresist removal

Abstract

We characterize the chemical constitutents of high dose implanted deep ultraviolet photoresist before and after dual-mode oxygen plasma processing, where a remote rf-plasma source is operated simultaneously with rf bias. Raman spectroscopy indicates that the organic composition of the crust comprises a mixture of sp2 graphite and sp3 diamondlike carbon structures. High dose ion implantation reduces the hydrogen content by about 50 at. % as measured by hydrogen forward scattering and explains the reduced optical emission signal intensity observed during crust removal. The crust thicknesses extracted from the secondary-ion-mass spectroscopy profile correspond well to prior scanning electron microscopy characterization [Kawaguchi et al., J. Vac. Sci. Technol. B (submitted)] and support the existence of a transitional layer between the hardened crust and the underlying photoresist. Angle-resolved x-ray photoelectron spectroscopy analysis of arsenic implanted photoresist shows that dual-mode plasma processing causes substantial oxidation deep into the bulk. This result contrasts with downstream plasma processing, which proceeds by a near-surface mechanism. In addition, surface arsenic levels increase by an order of magnitude, which suggests that ion bombardment does not significantly sputter the dopant.