Glycolic acid in hydrogen peroxide-based slurry for enhancing copper chemical mechanical polishing

The effects of glycolic acid (GCA) added into hydrogen peroxide (H2O2) or urea-hydrogen peroxide (U-H2O2) slurries on Cu-CMP performance were investigated. Experiments showed that GCA could prevent H2O2 or U-H2O2 from rapid decomposition and increase the active peroxide lifetime of the slurries. In addition, electrochemical studies from polarization and impedance experiments verified that copper removal efficiency could be enhanced by use of GCA. Meanwhile, a valid equivalent circuit for Cu-CMP system was proposed, and the fitting results provided a good index to surface planarization. Furthermore, GCA could shorten the range of isoelectric points between Cu film and α-Al2O3 abrasives. After a post cleaning, the particle contamination thus could be reduced due to the electrostatic repulsion. Our study proved that adding GCA into the U-H2O2 slurries with BTA could further improve the Cu-CMP performance.