A weak pattern random creation and scoring method for lithography process tuning

As the IC technology node moves forward, critical dimension becomes smaller and smaller, which brings huge challenge to IC manufacturing. Lithography is one of the most important steps during the whole manufacturing process and litho hotspots become a big source of yield detractors. Thus tuning lithographic recipes to cover a big range of litho hotspots is very essential to yield enhancing. During early technology developing stage, foundries only have limited customer layout data for recipe tuning. So collecting enough patterns is significant for process optimization. After accumulating enough patterns, a general way to treat them is not precise and applicable. Instead, an approach to scoring these patterns could provide a priority and reference to address different patterns more effectively. For example, the weakest group of patterns could be applied the most limited specs to ensure process robustness. This paper presents a new method of creation of real design alike patterns of multiple layers based on design rules using Layout Schema Generator (LSG) utility and a pattern scoring flow using Litho-friendly Design (LFD) and Pattern Matching. Through LSG, plenty of new unknown patterns could be created for further exploration. Then, litho simulation through LFD and topological matches by using Pattern Matching is applied on the output patterns of LSG. Finally, lithographical severity, printability properties and topological distribution of every pattern are collected. After a statistical analysis of pattern data, every pattern is given a relative score representing the pattern’s yield detracting level. By sorting the output pattern score tables, weak patterns could be filtered out for further research and process tuning. This pattern generation and scoring flow is demonstrated on 28nm logic technology node. A weak pattern library is created and scored to help improve recipe coverage of litho hotspots and enhance the reliability of process.