Characterization of TMAH based cleaning solution for post Cu-CMP application

Abstract

The cleaning of copper surface after chemical mechanical planarization (CMP) process is a critical step since the surface would be contaminated by a large number of slurry particles such as silica or alumina and organic residues such as benzo triazole (BTA). The presence of organic residues results in a hydrophobic surface, which leads to problems in particle removal and drying. A major function of a post copper CMP cleaning solution is to remove these organic contaminants without significant increase in the surface roughness. Alkaline or acidic cleaning solutions are usually preferred over neutral solutions since they can remove organic residues better. The objective of this work is to formulate an alkaline cleaning solution and characterize its efficiency on particle and BTA removal. The cleaning solution studied consists of tetra methyl ammonium hydroxide (TMAH) as the cleaning agent and arginine as the chelating agent. The removal of BTA is characterized using contact angle measurements and electrochemical techniques. The proposed cleaning solution showed good ability in removing BTA and silica particles from the copper surface and also yielded a lower surface roughness. Arginine facilitates complexing of Cu ions thereby preventing redeposition.