A system and methodology for monitoring and/or controlling a semiconductor fabrication process is disclosed. Scatterometry and/or ellipsometry based techniques can be employed to facilitate providing measurement signals during a damascene phase of the fabrication process. The thickness of layers etched away during the process can be monitored and one or more fabrication components and/or operating parameters associated with the fabrication component(s) can be adjusted in response to the measurements to achieve desired results, such as to mitigate the formation of copper oxide during etching of a copper layer, for example.