Stitch-avoiding Global Routing for Multiple E-Beam Lithography

In Multiple E-Beam Lithography (MEBL), a layout of an IC is partitioned into vertical stripes whose boundaries are called stitch-lines. Routing patterns in each stripe are written by different beams and/or in different writing passes. However, patterns cut by stitch-lines suffer from overlay errors resulting in severe pattern distortions. These distortions are mainly due to Via violation, Vertical Routing violation, or Short Polygon. In this paper, we have proposed a Stitch-avoiding Global Router. The proposed method selects the best possible global routing path for each net so that even a traditional detailed router can generate a Detailed Routing solution with fewer violations. Experimental results show that our proposed global router followed by a conventional detailed router generates solutions with 17.3%, 6.21% and 1.89% reduction in Via violations, Short polygon violations and routed wirelength respectively with no vertical routing violations, compared to those by traditional global routing.