Shot overlap model-based fracturing for edge-based OPC layouts

Abstract

In this paper, we develop a novel fracturing algorithm with shot overlap that is tailored towards rectilinear masks, such as those generated via edge based OPC software. Our proposed fracturing algorithm generates both the location and dosage of shots given the mask layout and mask making parameters. In the first step we heuristically cover the mask polygon with overlapping shots. Next, we incorporate the forward scattering and resist model in a least squares problem to compute the best dosage for all shots. Finally, we update the locations of the shot edges by computing the edge placement error between our simulated contour and the desired contour. One unique feature of our algorithm is that it can readily trade off between edge placement error and shot count by adjusting two input parameters. Compared to a commercially available non-overlapping shot software package, for a 400µm × 400µm micron SRAM unit with about 1 million polygons, our algorithm results in a 23% reduction in shot count, while increasing the weighted average EPE from 0.7 to 1 nanometers.

Benchmarking of Mask Fracturing Heuristics

“…This is consistent with recent work on mask fracturing [16] [17]. We set the CD tolerance γ = 2nm, and the minimum and maximum dimensions of a shot are 13nm and 1000nm, respectively.…”