Shot count reduction for non-Manhattan geometries: concurrentoptimization of data fracture and mask writer design
2013
VSB mask writers, which create patterns using a combination of rectangles and 45 degree triangles, are ill-suited to non-
Manhattan geometries. This issue is particularly acute for layouts which contain a large fraction of curvilinear “offangle”
patterns such as photonic or DRAM designs. Unable to faithfully reproduce the “off-angle” structures, traditional
VSB mask writers approximate the desired design using abutted rectangular shots or small shapes to smooth out line
edge roughness. Fidelity to the original pattern comes at a cost of increased shot count and reduced throughput.
Aselta has developed a novel fracture algorithm to dramatically reduce the shot count of such designs. Using a traditional
VSB pattern generator, the new algorithm provides significant shot count reduction. When combined with a modified
JBX-3200MV VSB, the shot count is reduced while maintaining the same level of fidelity. The data preparation software
tool has also the capability of trading off a more accurate level of fidelity with an even more reduced shot count.
The paper will first describe the basic principles of the fracturing algorithm and e-beam writer hardware configuration
then demonstrate the advantage of the method on a variety of patterns.
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