Methods for forming calibration standards for an inspection system and calibration standards are provided. One method includes scanning a first and a second specimen with an optical system. Master standard particles having a lateral dimension traceable to a national or international authority or first principles measurements are deposited on the first specimen. Product standard particles are deposited on the second specimen. In addition, the method includes determining a lateral dimension of the product standard particles by comparing data generated by scanning the two specimens. One calibration standard includes particles having a lateral dimension of less than about 100 nm deposited on a specimen. A distribution of the lateral dimension has a full width at half maximum of less than about 3%. The uncertainty of the lateral dimension is less than about 2%. Therefore, the standard meets the requirements for the 130 nm technology generation of semiconductor devices.