Calibration-aware spectroscopic ellipsometric inversion for thin-film metrology under instrument nonidealities

Calibration errors and instrument nonidealities can bias spectroscopic ellipsometric inversion when calibration and sample estimation are treated as independent operations. This work presents a calibration-aware framework that embeds incidence-angle, wavelength-axis, polarization-element, compensator-retardance, and spectral-response errors in the thin-film forward model. Reference-derived calibration covariance is propagated through constrained inversion, while sensitivity, Fisher-information, and cross-correlation metrics quantify identifiability. Eight single-layer films spanning 35–320 nm were evaluated against X-ray reflectometry and an independently calibrated commercial ellipsometer. The laboratory system achieved a mean absolute XRR difference of 0.49 nm, and the mean laboratory–commercial difference was − 0.39 nm with 95% limits of agreement from − 1.35 to + 0.57 nm. Under controlled instrument drift, prior-constrained refinement reduced thickness MAE from 2.25 to 0.78 nm and increased interval coverage from 74% to 93%, approaching the nominal 95% level. Routine inversion required 0.84 s per sample. The results establish a traceable calibration–inversion–uncertainty workflow for thin-film metrology under instrument nonidealities.