Evaluation of shaping gain adjustment accuracy using atomic force microscope in variably shaped electron-beam writing systems

A method for the fine evaluation of shaping gain adjustment, in which resist patterns are measured using an atomic force microscope (AFM), has been explained for the variably shaped electron-beam (EB) writing systems. The shaping gain coefficient was adjusted so that the length between two beams deflected by a shaping deflector is equal to a parameter given to the writing system. For the evaluation of the absolute values of the adjustment, the authors drew line and space patterns on a poly-methyl methacrylate (PMMA) resist. The authors measured the resist height at the shot boundary with an AFM. When the beam size is equal to the shot pitch, the resist height at the shot boundary becomes zero. From the beam size and the shaping-gain shift at which the resist height at the shot boundary becomes zero, beam-size error was calculated. From the beam-size error for various beam sizes, the shaping gain adjustment error of 0.3nm for the 1 mu m beam size and the shaping-offset error of 6.0 nm have been obtained.