1. A method comprising: illuminating a measurement site of an unfinished, multi-layer semiconductor wafer with illumination light; polarizing the illumination light before incidence on the semiconductor wafer; analyzing light collected from the measurement site of the semiconductor wafer in response to the polarized illumination light provided to the semiconductor wafer; detecting the analyzed light with a spectrometer; generating a measured spectral response of the measurement site of the unfinished, multi-layer semiconductor wafer from the analyzed light detected by the spectrometer, the measured spectral response comprising measurement data; determining a structural characteristic of the unfinished, multi-layer semiconductor wafer based at least in part on the measurement data; determining a dispersion metric associated with a layer of the unfinished, multi-layer semiconductor wafer based at least in part on the measurement data; determining a band structure characteristic indicative of an electrical performance of a portion of the multi-layer semiconductor wafer based at least in part on the dispersion metric; determining an estimate of one or more device performance metrics of the multi-layer semiconductor wafer, as if the unfinished, multi-layer semiconductor wafer were finished, based at least in part on the band structure characteristic and the structural characteristic; determining an adjustment in one or more subsequent process steps based on a difference between the estimated values of the one or more device performance metrics and one or more corresponding specified final device performance values, wherein the adjustment includes a change in a targeted nominal process value of a subsequent process step; and communicating an indication of the adjustment to a fabrication tool to perform the subsequent process step in accordance with the adjustment.