EBL Overlapping Aware Stencil Planning for MCC System

Abstract

Electron beam lithography (EBL) is a promising, maskless solution for the technology beyond 14nm logic nodes. 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 was extended into a multi-column cell (MCC) system to further improve the throughput. In an MCC system, several independent CPs are used to further speed-up the writing process. Because of the area constraint of stencil, the MCC system needs to be packed/planned carefully to take advantage of the characters. In this article, we prove that the overlapping aware stencil planning (OSP) problem is NP-hard. Then we propose E-BLOW, a tool to solve the MCC system OSP problem. E-BLOW involves several novel speedup techniques, such as successive relaxation and dynamic programming. Experimental results show that, compared with previous works, E-BLOW demonstrates better performance for both the conventional EBL system and the MCC system.