Preferential copper electrodeposition at submicrometer trenches by consumption of halide ion

Abstract

Preferential copper electrodeposition at submicrometer trenches in an acid copper sulfate electroplating bath by addition of only two components [bromide ion and polyethylene glycol (PEG)] is observed. Strong suppression by PEG is observed by the addition of Br- compared with the addition of Cl-. It is supposed that halide ions work as an adhesive between PEG and the copper surface. During electroplating, halide ions are consumed and the concentration of halide ions in submicrometer trenches is reduced by diffusional limitation. The reduction of halide ion concentration weakens the PEG adsorption and thus preferential copper electrodeposition at submicrometer trenches is realized. Nonuniform deposition observed by filling experiments is explained by this model.