Optical angular scatterometry: In-line metrology approach for roll-to-roll and nanoimprint fabrication

Abstract

Metrology is an essential aspect of nanomanufacturing. Increasingly, nanoscale three-dimensional features are demanded for advanced applications, increasing the demands on metrology. New fabrication techniques such as roll-to-roll (R2R) processes are being developed for manufacturing large-area nanotechnology products such as wire-grid polarizers (WGP), metal-mesh grids, and metamaterials. Angular scatterometry has demonstrated noncontact, optical capabilities for characterizing WGP and photoresist structures with sub-100 nm dimensions. However, existing implementations are not applicable to real-time R2R nanofabrication due to both a requirement of rotating a small sample over a range of angles and measurement times that are incompatible with a moving R2R web. This work demonstrates a high-speed approach (2.5 kHz scanning) to angular scatterometry where the optical beam is scanned rather than the sample mount. The design uses a scanning mirror and high numerical aperture (NA) optics to vary the incident angle over a range from ∼29° to ∼59°. Approaches to increase the angular range are discussed. The scatterometry results are in good agreement with off-line scatterometry results for plane surface, 1D, and 2D patterned samples.