Sub-50-nm pitch size grating reference for CD-SEM magnification calibration

We have developed a novel multi-layer grating pattern with a sub-50-nm pitch size for CD-SEM magnification calibration instead of the conventional 100-nm pitch grating reference. The sub-50-nm pitch size grating reference was fabricated by multi-layer deposition of alternative two alternating materials and then the material-selective chemical etching of the cleaved cross-sectional surface. A line and space pattern with 10-nm pitch size was easily resolved and a high-contrast secondary electron image of the grating pattern was obtained under 1-kV acceleration voltage using CD-SEM. The uniformity of the 20-nm pitch size of the grating was less than 1 nm in 3σ. The line edge roughness of the grating pattern was also less than 1 nm. Such a fine and uniform grating pattern will fulfill the requirements of a magnification calibration reference for next-generation CD-SEM.