Auxiliary pattern-based optical proximity correction for better printability, timing, and leakage control

Abstract

Listen

Translate article

Optical proximity correction OPC is a mandatory resolution enhancement technique RET to ensure the printability of layout fea- tures in silicon. The most prominent OPC method, model-based OPC, alters the layout data for the photomask that enables drawn layout fea- tures to be accurately reproduced by lithography and etch processes onto the wafer. This technique in various forms has now become stan- dard in integrated circuit IC manufacturing at 0.18 m and below. How- ever, model-based OPC is computationally expensive and its runtime increases with technology scaling. The cell-based OPC approach im- proves runtime by performing OPC once per cell definition, as opposed to once per cell instantiation in the layout. However, cell-based OPC does not comprehend intercell optical interactions that affect feature printability in a layout context. This leads to printability, and conse- quently, performance and leakage, degradation. In this work, we propose auxiliary pattern-enabled cell-based OPC to improve printability of cell- based OPC, while retaining its runtime advantage. Auxiliary patterns AP are nonfunctional poly features that are added around a standard cell to shield it from optical proximity effects. We present the AP-based OPC approach and demonstrate its advantages over cell-based and model-based OPC in terms of printability as well as timing and leakage variabilities. AP-based OPC improves the edge placement error over cell-based OPC by 68%. To enable effective insertion of AP in cell in- stances at a full-chip layout level, we propose a dynamic programming DP-based method for perturbation of detailed placement. Our approach modifies the detailed placement to allow opportunistic insertion of AP around cell instances in the design layout. By perturbing placement, we achieve 100% AP applicability in designs with placement utilization less than 70%. AP-based OPC also reduces leakage and timing variability compared to conventional cell-based OPC. We further demonstrate that AP insertion achieves timing and leakage variability comparable to that of model-based OPC. © 2008 Society of Photo-Optical Instrumentation Engineers.