A technique for in situ monitoring of polishing processes and other material removal processes employs a quartz crystal nanobalance embedded in a wafer carrier. Material removed from the wafer is deposited upon the surface of the crystal. The resulting frequency shift of the crystal gives an indication of the amount of material removed, allowing determination of an instantaneous removal rate as well as a process endpoint. The deposition on the quartz crystal nanobalance may be controlled by an applied bias. Multiple quartz crystal nanobalances may be used. In a further embodiment of the invention, the quartz crystal nanobalance is used to detect defect-causing events, such as a scratches, during the polishing process.