As an alternative to conventional chemical mechanical polishing (CMP) for the planarization of copper layers on electronic circuits, the electrochemical mechanical polishing (ECMP) process in alkali-based solution was investigated in this work. The influence of the polishing pad materials on the polishing process was studied, and the hard polyurethane polishing pad was shown to eliminate the "dishing effect". The polishing conditions, such as the pad rotating speed, concentration of H 2 O 2 , and the amount of BTA additives were optimized to control the planarization performance. As a result, good planarization uniformity was obtained not only in small scale (30 µm) trenches but also in very large scale (a few mm) patterns with a single step ECMP process.