Another performance test we ran was to scan a programmed line edge roughness (LER) sample with CD-AFM2 using a J-tip. This type of LER sample was originally developed for testing CD-SEM measurements of LER during lithography development and optimization.38 The actual feature sidewalls are normally close to vertical, and may also be slightly re-entrant depending upon the details of the etch for a given sample. More discussion is included in the Appendix, but the primary characteristic of the programmed LER features is a periodic variation in linewidth having different spatial frequencies and amplitudes on different targets.