Identifying defects in photolithographic patterning is a persistent challenge in semiconductor manufacturing. Well-established optical methods in current use are jeopardized by upcoming sub-20 nm device dimensions. Volumetric processing of focus-resolved images of defects is presented using simulated and experimental examples. Defects are revealed using 193 nm light as the focus and illumination conditions are optimized. The data analysis protocol exploits the focal range of defect-based scattering leading to the observation of defects as small as 16 ± 2 nm (k=1) in critical dimension. Quantitative metrics to compare two-dimensional and three-dimensional imaging indicate possible fourfold improvements in sensitivity using these methods.
Citation: Optics Express
Pub Type: Journals
Defect metrology, Volumetric data analysis, Subwavelength structures, Three-dimensional image processing, Industrial inspection, Defect understanding