Lossless Compression Algorithm for REBL Direct-Write E-Beam Lithography System

Future lithography systems must produce microchips with smaller feature sizes, while maintaining throughputs comparable to those of today’s optical lithography systems. This places stringent constraints on the effective data throughput of any maskless lithography system. In recent years, we have developed a datapath architecture for directwrite lithography systems, and have shown that compression plays a key role in reducing throughput requirements of such systems. Our approach integrates a low complexity hardware-based decoder with the writers, in order to decompress a compressed data layer in real time on the fly. In doing so, we have developed a spectrum of lossless compression algorithms for integrated circuit layout data to provide a tradeoff between compression efficiency and hardware complexity, the latest of which is Block Golomb Context Copy Coding (Block GC3). In this paper, we present a modified version of Block GC3 called Block RGC3, specifically tailored to the REBL direct-write E-beam lithography system. Two characteristic features of the REBL system are a rotary stage and E-beam corrections prior to writing the data. The former results in arbitrarily-rotated layout imagery to be compressed, and as such, presents significant challenges to the lossless compression algorithms, including Block GC3. We characterize the performance of Block RGC3 in terms of compression efficiency and encoding complexity on a number of rotated layouts at various angles, and show that it outperforms existing lossless compression algorithms.