Electron Beam direct writing (EBDW) technology is the most cost-effective lithography tool for small-volume logic-LSI fabrication. The EB exposure time will be greatly reduced by applying character-projection (CP) aperture. But the applicable number of CP aperture is limited to 25-400 depending upon EB lithography apparatus. The cell-based logic LSIs are composed of standard-cells (SCs) whose number is 400-1000. Therefore, it is impossible to implement all SCs as CP apertures, because the SCs are placed to 4-directions in general. We had proposed the new technique named 'Character-Build (CB) standard-cell', and demonstrate the most of the combination-logic SCs can be composed by only 17 CP apertures. In this paper, not only combination-logic SCs but also sequential-logic SCs are considered. The number of EB-shots and the chip-area are estimated for some sample circuits.
Compared to the simply-limited SCs, The EB shot number is 30-40% reduced by using proposed CB standard-cell, when the CP aperture numbers are 20-30. Moreover, CB standard-cell was advantageous in the module area. Considering 2-directional placement of SCs, the combination of the EB apparatus with 50-100 CP apertures and the CB
standard-cell technique may be the best method for high-speed EB direct-writing.
EB direct writing technology for small-volume fabrication LSIs is cost-effective compared to optical lithography. The new standard cell layout technique called “Character-Build cell” is developed in order to increase the utilization ratio of character projection (CP) mask. The various kinds of standard cells can be composed by the combination of "character” cells. The 86% of 223 standard cells can be composed by 17 “character” cell using this technique. It is estimated that the great portion of random logic area can be exposed by about 50 CP mask. Therefore the throughput of EB direct write using this layout technique will be greatly higher than that of the conventional layout.