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Electron Beam Calibration Method for Character Projection Exposure System EX-8D

A character beam calibration method has been developed for the electron beam exposure system EX-8D. The method concerns the character selection deflector, beam current density uniformity, beam size, direction, and position on the target. For the current density, the uniformity of less than 1.4 has been obtained in a 2-mm-square field. The beam size and the direction has been calibrated with an error of less than 1 nm in a 1-µm-square character beam. The overall error of the resist pattern size exposed by the character beam was estimated to be 7.2 nm. For the beam position on the target, the calibration accuracy of 0.023 µm has been obtained by a pattern matching method. After applying the calibration, 0.15 µm line-and-space patterns were exposed with good resolution by using the character beam. Also, a test pattern has been written with 0.02 µm stitching accuracy between variable shaped and character beams.