The electrochemical mechanical planarization (Ecmp) process is a revolutionary planarization technology uniquely combining removal rate controlled by charge with superior planarization efficiency in the near no-shear regime. A planarization mechanism for Ecmp is proposed to explain the high planarization efficiency. Meanwhile, the effects of applied voltage on removal rate and planarization efficiency are discussed. The electrical feature allows Ecmp to be a planarization process with removal rate independent of downforce, enabling a wide removal rate window and high planarization efficiency. (C) 2006 The Electrochemical Society.