In order to improve our understanding of the fundamental surface processes associated with the chemical mechanical planarization (CMP) of metals, we have developed an experimental tool that combines the high resolution mass sensing capabilities of the quartz crystal microbalance (QCM) with a triboelectrochemical testing system. A electrochemical QCM is combined with a polishing tool and force sensor in order to perform controlled surface abrasion while simultaneously monitoring mass changes and electrochemical signals at the metal/solution interface. This system can be used to simulate a metal polishing process with in situ surface measurement capabilities. Typical parameters that can be measured include etch rates, polishing rates, and repassivation kinetics via changes in the resonance frequency of the quartz crystal before, during, and after polishing. Simultaneous measurements of electrochemical parameters, such as the electrode current or open circuit potential, provide a direct correlation between polishing parameters and electrochemical signals. The behavior of copper in various solutions illustrates the capabilities of this technique and highlights the complexities of the metal polishing process. The influence of pH, benzotriazole, peroxide, and several slurry chemistries are examined. (C) 2004 The Electrochemical Society.