Photoresist and Fluorocarbon Postplasma Etch Residue Removal Using Electrochemically Generated Radical Anions

Abstract

Integration of new materials into semiconductor manufacturing sequences demands cleaning processes that are compatible with copper and low dielectric constant (low-k) materials. Conventional oxidative cleaning processes are currently used to remove fluorocarbon-based postplasma etch residues; however, these processes are generally incompatible with organic-containing low-k candidate materials. A photoresist removal and etch residue cleaning process based on reductive naphthalene radical anion chemistry has been developed and evaluated on patterned low-k etch residue samples. Solutions of naphthalene radical anions are generated by electrolysis using platinum electrodes in a split electrochemical cell. The radical anion process cleans effectively at room temperature and thus requires no elevated temperature steps for film removal or surface drying. The removal mechanism is a synergistic combination of solvent swelling and fluorocarbon attack, resulting in effective etch-residue removal; removal from vias as small as 130 nm has been demonstrated. Preliminary investigations indicate chemical compatibility with both Coral and methylsilsesquioxane low-k materials. © 2008 The Electrochemical Society.