Development of data conversion system for electron beam projection lithography (EPL) mask

Electron beam (EB) lithography has long been used for fabricating advanced ULSIs. Recently, to increase the writing throughput, electron beam projection lithography (EPL) technology has been proposed (100kV acceleration voltage and 20-30 muA total currents). When we implement this technology to mass production, the data conversion system and EPL mask, which is different from conventional optical mask, have to be developed. In EPL mask conversion system, it is necessary to divide a full chip data into 1mm X 1mm (250um X 250um on the wafer) sub-fields, which size is as same as the EPL shot size with format conversion. In this paper, we show the data conversion system that converts pattern data (GDS II) to EPL mask data. This system can maintain the hierarchy data structure in the dividing process to sub-fields. The patterns that located on the boundary between neighboring sub-fields will be treated as belonging in either field for the prevention of critical division. We have developed a data conversion system for EPL mask that can divide the device data with high speed and high quality.