Effect of Pattern Layout and Dissolved Oxygen in CO_2 Rinse Water on Cu Corrosion during Post-Etch Cleaning

摘要

When post-etch cleaning was carried out in Cu dual-damascene process, Cu at the bottom of isolated via was etched out especially in the wafer edge, and this would become a critical issue as device scale is shrunk. The corrosion was caused in the rinse step rather than chemical cleaning step because dissolved oxygen in rinse water from the air increased oxidation-reduction potential (ORP) and CO_2 included in the rinse water for preventing wafer electrification decreased pH. The corrosion was found to be suppressed by increasing dummy pattern density and by controlling atmosphere and pH of the rinse water.