Cyclic etching of copper thin films using HBr and Ar gases

Abstract

Sequential cyclic etching of copper thin films was performed using HBr/Ar gas and Ar plasma. The first step involved the formation of CuBrx layers by exposing copper thin films to HBr/Ar gas, and the second step involved the removal of the CuBrx layers by Ar ion sputtering. HBr/Ar gas was used to form the CuBrx layers, and the growth of CuBrx layers could be saturated under certain conditions. Ar ion sputtering was optimized under the condition that led to the removal of the CuBrx layer and prevented the copper sputtering. The formation and removal of the CuBrx layers were confirmed by x-ray photoelectron spectroscopy analysis. The etch depth per cycle was estimated to be approximately 1.2 nm. The 120-cycle etching of copper films patterned with an SiO2 hard mask exhibited good etch profiles without any redepositions or etch residues. The cyclic etching of copper thin films using HBr/Ar gas was proposed as a promising etching technique.