  Electron beam lithography (EBL) is a promising maskless solution for the
technology beyond 14nm logic node. To overcome its throughput limitation,
industry has proposed character projection (CP) technique, where some complex
shapes (characters) can be printed in one shot. Recently the traditional EBL
system is extended into multi-column cell (MCC) system to further improve the
throughput. In MCC system, several independent CPs are used to further speed-up
the writing process. Because of the area constraint of stencil, MCC system
needs to be packed/planned carefully to take advantage of the characters. In
this paper, we prove that the overlapping aware stencil planning (OSP) problem
is NP-hard. To solve OSP problem in MCC system, we present a tool, E-BLOW, with
several novel speedup techniques, such as successive relaxation, dynamic
programming, and KD-Tree based clustering. Experimental results show that,
compared with previous works, E-BLOW demonstrates better performance for both
conventional EBL system and MCC system.
