Novel CD-SEM calibration reference consisting of 100-nm pitch grating and positional identification mark

摘要

We fabricated a grating reference with EB cell projection lithography and silicon dry etching, instead of conventional 240-nm pitch grating references fabricated with laser-interferometer lithography and anisotropic chemical wet etching. We developed a novel 100-nm pitch grating reference based on our grating reference for critical dimension-scanning electron microscope (CD-SEM) calibration. We obtained high-contrast secondary electron signals and uniform grating patterns within 3 nm in 3σ during CD-SEM measurements because we eliminated the proximity effect of EB exposure. The reference has an array of 100-nm grating cells in the x- and y-directions. Each cell consists of a 100-nm grating unit, an X-Y coordinate number in the array, and an addressing mark for the CD-SEM to identify the calibration position. These positional identification marks enable accurate calibration by specifying the location of the grating and the number of calibrations. Also, the pitch size of the reference grating can be accurately calibrated by optical diffraction angle measurements with a deep ultraviolet (DUV) laser.