Influences on coordinate measurement uncertainty for an electron-beam based mask comparator operating in vacuum

摘要

The PTB as the national metrology institute of Germany offers traceable pattern placement calibrations on two-dimensional measuring objects, like e.g. photomasks. In addition to the optical mask measurement system LMS 2020, the PTB also applies an electron-optical metrology system (EOMS) for its investigations. The main advantage of the EOMS is the laser interferometer operating in vacuum, thus the measurements do not require refractive index correction. The influences on length and coordinate measurement uncertainty of the EOMS will be analysed and compared with the current requirements from photomask industry.