A major challenge in modern semiconductor, photonic, andquantum technology is the accurate characterization of ultrathin (<100 nm) patterns withever-decreasing lateral feature sizes (<25 nm).In this study, we showcase ellipsometric porosimetry (EP) as an alternative,scalable metrology for model channel hole patterns. The critical dimensions ofsuch features are typically below 100 nm,and thus their diameters can be determined via insitu optical observation of capillary evaporation-driven refractiveindex changes based on classical thermodynamic principles. We demonstrate thatthe EP-derived diameters of the model structures correlate well with both theexpected values and those obtained from optical critical dimension (OCD)metrology. Since the accuracy of OCD decreases when probing deep into thesubwavelength regime (<190 nm),EP emerges as a complementary metrology candidate, as its highest accuracy istypically for feature sizes of 1–25 nm. The method presented herecan also be extended to more complex anisotropic structures.
