Sub-nanometer line width and line profile measurement for CD-SEM calibration by using STEM

Abstract

The novel method of sub-nanometer accuracy (uncertainty) for the line width and line profile measurement using STEM (Scanning Transmission Electron Microscope) images is proposed to calibrate CD-SEM line width measurement. In accordance with the proposed method, the traceability and reference metrology of line width measurements are established using Si lattice structures. First, we define two interfaces of Si-SiO2 and Si-Air. The interface of Si-SiO2 is defined as the end of Si lattice structure, and the interface of SiO2-Air is defined using image intensity of STEM image after metal coating. Second, an image magnification is calculated using 2D Fourier analysis of a STEM image. Third, the edge positions of the line are detected by Si lattice patterns and image intensity. Using the proposed method, the estimated accuracy less than 0.5 nm for the line width of 50 nm is established.