A multi-layer immersion medium monitoring system for a lithographic process monitors characteristics of an immersion medium of a semiconductor manufacturing process. The multi-layer immersion medium includes at least a first liquid of a first density (or viscosity) and a second liquid of a lower density (or viscosity), both of which are interspersed between a final optical component and a semiconductor layer. The higher density layer is provided to reduce turbulence in the immersion medium during the lithographic processes. A scatterometry system monitors optical characteristics of the multi-layer immersion medium to effectuate control of a lithographic process.