Visible light angular scatterometry is investigated for sub-100 nm line metrology. Measurement sensitivities to small variations in line dimensions are examined and some observations are made on the measurement conditions leading to improved sensitivities even for 20 nm CD. Experimental results with good accuracies are also shown for red light angular measurements of PMMA gratings made by e-beam lithography and nanoimprint lithography. The theoretical and experimental studies show high sensitivity and accuracy in characterization of the geometry and dimensions of nano-lines, particularly in measuring the polymer residue thickness of nanoimprinted polymer gratings and the undercut line profiles resulting from e-beam lithography. The results promote using this low cost and non-invasive technique to examine and control some underlying lithographic processes in nanofabrication.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.