Mask data preparation is a complicated process because many kinds of pattern files and jobdeck files flow into mask manufacturers. This situation has a significant impact on data preparation operations especially in mask manufacturers. In this paper, we propose a solution to this problem: use of unified mask data formats for EB writers and a model of data preparation flow from a device manufacturer to an EB writer. The unified formats consist of pattern data format named "NEO", and mask layout format named "MALY". NEO is a stream format which retains upper compatibility to GDSII and has higher compression rate than GDSII. NEO is intended to be a general input format of Variable-Shaped-Beam (VSB) mask writers in principle, not particularly designed for any specific equipment or software. Data conversion process between mask writers being taken into account, NEO requires some constraints for VSB mask writers, such as removal of overlapping figures. Due to many differences in jobdeck syntax and functions among mask writers, it is a complicated task to edit or modify a jobdeck, and convert it into another format. MALY is a text-based format whose purpose is to standardize mask layout information among mask writers. This unification of mask layout information optimized for EB writers is expected to reduce workload of mask data preparation significantly. Besides the information described in MALY, some other information specific to the target EB writer, such as drawing parameters, has to be prepared separately. This paper illustrates a model of data flow and benefits of using these unified formats. The format and the data flow are effective in reducing data handling cost, providing flexible data handling solution. Applying the handling flow using NEO and MALY would result in reducing the load on mask manufacturers. Moreover, device manufacturers would be freed from the need to specify the mask writer to be used when ordering masks to mask manufacturers.