Study on the impact of X-ray energy and beam size on CD-SAXS measurement precision

With the development of the semiconductor industry below the 7nm node, Critical Dimension Small Angle X-ray Scattering (CD-SAXS) has emerged as a powerful tool for quantitatively measuring nanoscale deviations. In this work, the effects of X-ray beam sizes and photon energies on accuracy of critical dimension measurements were investigated. Critical dimensions measured by different spot sizes of beam have different deviations from the expected values, a too large or too small beam size is not conductive to the improvement of confidence intervals. As the incident energy increases, X-ray transmission rate increasing while scattering cross section was decreased, result in the ratio of signal to noise of diffraction peaks were observed to decrease gradually, and reducing the accuracy of CD-SAXS measurements. An optimal accuracy obtained at 12 keV with an smaller beam size using an effective trapezoid model yielded an average pitch of 100.4 ± 0.2 nm, width of 49.8 ± 0.2 nm, height of 130.0 ± 0.2 nm, and sidewall angle below 1.1 ± 0.1°. These results can provide crucial guidance for the future development of CD-SAXS laboratories and the construction of X-ray machines, offering robust support for research in related fields.