A fundamental study was undertaken to evaluate the usefulness of a sulfonic acid-based chemical system for the removal of tantalum under electrochemical mechanical planarization conditions. Tantalum as well as copper samples were polished at low pressures ͑ϳ0.5 psi͒ under galvanostatic conditions in dihydroxy benzene sulfonic acid ͑DBSA͒ solutions maintained at different pH values. At a current density of 0.5 mA/cm 2 and pH 10, tantalum removal rate of ϳ200 Å/min with a 1:1 selectivity to copper has been obtained in 0.3 M DBSA solutions containing 1.2 M H 2 O 2 . The presence of a small amount ͑ϳ0.1%͒ of colloidal silica particles is required to obtain good removal rates.

Chemical formulations for the electrochemical mechanical planarization (ECMP) of copper must contain constituents that are stable at anodic potentials. A key component of the formulation is a corrosion inhibitor, which is required to protect low lying areas while higher areas are selectively removed. Organic compounds, which adsorb on copper at low overpotentials and form a film by oxidation at higher overpotentials, may be particularly useful for ECMP. The objective of this work is to evaluate the effect of two inhibitors on copper dissolution in oxalic acid based systems using an electrochemical quartz crystal microbalance (EQCM) technique. By recording current as well as mass changes during the application of potential to electrodeposited copper films, the extent and mechanism of inhibition of sulfhydryl based acid (SBA) inhibitor has been explored.

Back End of Line (BEOL) cleaning of copper based structures requires chemical formulations that can remove copper oxide selectively without corroding copper and etching the dielectric. Many commercially available semi-aqueous and all aqueous formulations claim to meet these criteria. These include semi-aqueous fluoride strippers (SAF) and all- aqueous ammonium phosphate based chemical systems.This paper will report the results from a fundamental study undertaken to evaluate the performance of a semi-aqueous fluoride formulation in removing copper oxide films of controlled thickness grown on copper. The thickness and composition of the oxide films were determined electrochemically using cathodic reduction technique. Electrochemical impedance spectra of samples immersed in the formulation have been measured as a function of time to follow copper oxide dissolution and the data have been analyzed to detect the transition of copper oxide to copper.

The effect of anodic polarisation on dissolution of copper in hydroxylamine based chemical systems has been studied using a quartz crystal microbalance technique to evaluate their use in electrochemical mechanical planarisation processes. Copper dissolution in hydroxylamine solution increases with respect to overpotential g and dissolution rates as high as 600 nm min 21 have been obtained at an overpotential of 750 mV. The effectiveness of benzotriazole (BTA) in inhibiting copper dissolution in these chemistries was also tested. It was found that BTA is effective in inhibiting copper dissolution only at lower overpotentials ((250 mV).

No abstract