Absorbing assist pattern technique (A2PT) for effective sidelobe control for attenuated phase-shifting masks in optical projection lithography

摘要

A novel technique of sidelobe suppression based on absorbing assist pattern is introduced. Chrome shields are placed exactly at the position, where sidelobes appear. The effectiveness of this technique for sidelobe control is demonstrated by simulation and experimental results. The resulting process window enlargement for 180 nm contacts is investigated. Corresponding mask making issues are discussed.