Novel CD-SEM calibration reference patterned by EB cell projection lithography

A silicon grating pattern with a 100-nm pitch size for calibration of electron-beam (EB) metrology systems was formed by EB cell projection writing using a grating stencil mask and dry etching. According to the evaluation results from a critical-dimension scanning electron microscope (CD-SEM), the uniformity of the pitch size in a 1.8 x 1.8-mm chip was smaller than 3 nm within 3 sigma in the x and y directions. The obtained 100-nm pitch size was calibrated by DUV laser diffraction. The difference between designed 100-nm pitch size and the calibrated pitch size by DUV laser diffraction was smaller than 0.1 nm. It is thus concluded that more precise calibration of the CD-SEM using this 100-nm pitch grating is expected compared with conventional calibration using 240-nm pitch reference grating fabricated by laser-interferometer lithography and anisotropic chemical etching.