Characterization of phosphate electrolytes for use in Cu electrochemical mechanical planarization

Electrochemical mechanical planarization (ECMP) is a potential replacement or complement to conventional chemical mechanical planarization (CMP) techniques. ECMP can operate at very low downforces (<1.0 psi), potentially without slurry particles or oxidizers, and can also be tailored to achieve specific dissolution rates via applied potential. Through the modification of a phosphate-based electrolyte by the use of benzotriazole (BTA), a possible ECMP electrolyte was developed. Utilizing a rotating disk electrode (RDE), a broad range of electrolyte characteristics were screened. The most important parameters investigated were pH, salt concentration, and BTA concentration. The optimal electrolyte composition was found to be around 1 M potassium phosphate with a pH value of 2. Removal rates varied from 750 to 2500 nm min−1 within an operating potential window from 0.5 to 1.0 V vs. Ag/AgCl reference electrode.