Mask fabrication costs can be significantly aggravated by OPC complexity. This increased complexity is presumably needed to accurately render 2-D configurations. The humble line-end is one of the most difficult 2-D configurations to print accurately, when considering process margin requirements and mask fabrication constraints. In this paper, the requirements for proximity corrected line-end structures will be explored and a pattern complexity metric will be proposed to compare relative mask cost versus line-end lithographic performance. Many types of correction shapes are available to improve process margin for line-ends. However, the cost of producing these various line-end configurations can vary dramatically. Using both a simple optical model to simulate line-end performance through focus offset and a cost metric based on fracture primitive count, a comparison of six types of lines ends for correction and process efficiency will be undertaken. Each of the six line-end corrections will attempt to produce equally effective silicon line-end shapes. Line-ends will be evaluated based on shortening (pullback), pinching, and bridging characteristics. Line-end lithographic behavior will be characterized through all process window boundary conditions. The objective of this study is to quantify the tradeoffs among three variables: mask cost, process-window robustness, and design tolerance margin. In addition, through the study of proximity effects on the various line-end types, the possibility of mixing expensive but high performance line-ends with simpler less aggressive line-ends to reduce reticle cost while maintaining or increasing correction fidelity will be studied.
展开▼
