Improved Cleaning Process for Etch Residue Removal in an Advanced Copper/Low-k Device without the Use of DMAC (Dimethylacetamide)

Abstract

Plasma dry etching processes are commonly used to fabricate sidewalls of trenches and vias for copper / low-k dual damascene devices. Typically, some polymers remain in the trench and at the via top and sidewall. Other particulate etch residues are may remained in the bottom and on the sidewalls of vias. Generally, the particulate consists of mixtures of copper oxide with polymers. The polymers on the sidewalls and the particulate residues at the bottom of vias must be removed prior to the next process step. Small amounts of polymer are intentionally left on the sidewalls of trenches and vias during the etching in order to achieve a vertical profile and to protect the low-k materials under the etching mask. Until now, the industry has relied mainly on organic solvent containing mixtures to clean etch / ash residues from such devices. The effectiveness of available residue removers varies with the specific process and also depends on which new integration materials are used. New materials typically include Cu, TaN, low-k dielectrics and others [1-. Solvent content is thought to aid the removal of polymer residues and particulates produced during plasma dry etching processes. Therefore, in the past we have used a residue remover which contains DMAC (dimethylacetamide). But the use of DMAC is banned in microelectronic fabrication facilities in Europe because of its toxicity. Thus we wanted to find and evaluate a DMAC-free residue remover for removing polymer residues while maintaining high selectivity to the copper and ILD films.