MAIN-FIELD STITCHING ACCURACY ANALYSIS IN ELECTRON-BEAM WRITING SYSTEMS

A new evaluation method for main-field positioning error for electron beam (E-Beam) writing systems has been developed. Main-field distortion caused by system-based main-field positioning error such as contamination charging, deflector calibration error, substrate height error and so on is the main factor impairing accuracy in E-Beam writing systems. Main-field distortion after elimination of deflection distortion is classified into four modes. The origin of main-field positioning error can be estimated by investigating the behavior of these four modes of main-field distortion. This method has been applied to the variable shaped beam (VSB), vector scanning, and continuously moving stage E-Beam system. Contamination charging problems in the final lens surface in opposition to substrate and problems in the deflector calibration method have been found. Main-field positioning error of the E-Beam system decreased from 0. 1 mum to 0.04 mum after solving the above problems. The evaluation method for main-field positioning error has been proved to be very effective in accuracy improvement of E-Beam systems.