Calibration of 25-nm Pitch Grating Reference by X-ray Diffraction

Abstract

We have developed grazing incidence x-ray diffraction pitch calibration system with wavelength of 0.1540593 nm (Cu Kα1 line). In order to ensure consistency of this calibration system with currently used deep ultra violet (DUV) laser diffraction pitch calibration system, we measured average pitch of a 100-nm pitch grating reference for CD-SEM. The average pitch determined by the x-ray diffraction agreed with that determined by the DUV laser diffraction within the range of expanded uncertainty. We measured average pitch of a next generation 25-nm pitch grating for which DUV laser no longer works. We have successfully detected more than ten sharp diffraction peaks corresponding to the 25-nm period. The average pitch of the grating was measured in high-accuracy with expanded uncertainty of 40 pm. The result agreed well with that determined by metrological atomic microscope (AFM) within the range of expanded uncertainty.