DFM Viewpoints of Cell-level Layout Assessments and Indications forConcurrent Layout Optimization

摘要

Design-for-manufacturing (DFM) is becoming an actual design practice among IC manufacturers, designers andEDA companies. Layout assessment by design-rule-check (DRC) using EDA tools is a common practice today to ensurewell-manufactured design geometries. Standalone DFM tools, which require iteration loops of DFM analysis and fixing,do not fit well in design flows and are considered cumbersome. A better layout assessment method for DFM issues isrequired: one that gives actionable feedback, and that can be used with automatic optimization in early design stages.The latter is needed to avoid costly design re-spins that will consume critical time-to-market as well as use a lot ofengineering resources, reticles and wafer material costs. For example, a DFM checking tool may report the hotspot typesand locations, but this information is not sufficient for designers to decide tradeoffs between different fixing choices andto take care of trade-off between physical and electrical design constraints at the same time. When model-basedproperties are introduced such as lithographic contour, the tradeoffs between rule-based and model-based properties canonly be resolved by the automatic and concurrent optimization. This work demonstrates a methodology of DFM scoring of layout based on preferred rules compliance, lithographyGATE printability, as well as the layout fixing. The electrical impact on gates is analyzed and showed reduced variability(compared to nominal behavior) in gate performance. Designers can get visual feedback of the layout quality, as well asimprovement suggestions. Takumi TKE software is used to demonstrate automatic and concurrent optimization. Themethod applies to both cell-level and custom designs.