Fogging Effect Consideration in Mask Process at 50 KeV E-Beam Systems

To achieve higher resolution and critical dimension (CD) accuracy in mask fabrication, 50KeV E-beam systems are used widely. However, as a high acceleration system is adapted, the degree of fogging effect caused by multi-scattering electrons becomes more serious. Although considerable efforts have been made, fogging effect cannot be removed perfectly, therefore several compensation techniques are applied instead. Fogging effect not only deteriorates CD uniformity but also makes mean to target (MTT) control difficult. Moreover, Fogging effect causes proximity effect correction (PEC) error according to PEC methods such as dose modulation type usually used in variable shaped beam (VSB) system and GHOST type commonly used in Gaussian beam system. In this paper, we investigated the fogging effect under the various exposure conditions at raster scan Gaussian beam system and VSB system experimentally and analytically.