Limit of Line End Shortening Correction under Single Exposure in 193 nm Immersion Lithography

Abstract

As the lithography starts to approach the limit of 193 nm immersion imaging capability under single exposure, successful development of a lithographic process rely on the good balance of the process parameters, such as the exposure latitude and depth of focus for the dense, semi-dense, isolated structures, MEF, LWR, proximity bias, etc. Such balance requires very good understanding of the inter-relationship among them and ways to give reasonable specification to the important materials such as photoresist and photomasks. Although, relatively speaking, 1-dimensional structures, such as, line and space or even square contacts are relatively easy to understand and model with accurate simulations, which is close to perfect, 2-dimensional structures are not easy to understand physically and the simulation for them are up to larger errors. Since previous study on this subject was either done at larger ground-rules or lack of good physical understanding in the simulation, this paper will use both experimental wafer measurement data and physical modeling to probe the limits for the OPC correction of line (or space) end shortening structures at around 50 nm dimensions. Several structures will be studied in theory and wafer data.