| Popis: |
The effect of assist feature optical proximity correction (OPC) has been well examined in 248nm lithography. The design of scattering bars is governed by rules that determine their ideal size and placement and for 248nm lithography have been successfully applied to improve the process latitude for 130nm features. However, assist feature OPC has not been explored for use in 193nm lithography. The objective of this paper is to determine the effectiveness of assist features, specifically scattering bars, in 193nm lithography using established rules for scattering bar size and placement. The experiment consists of a binary reticle with scattering bars of different size and placement. The exposures are obtained on an ASML 5500/950 scanner using conventional, annular and quasar illumination. The results of individual process latitude are examined for 100nm features from dense through isolated lines with no OPC applied to obtain a baseline process. The use of assist feature OPC is examined as a means to improve common and individual process latitudes. However, the initial results indicate that the existing rules for scattering bar design are not adequate to produce a useable process with 193nm lithography. The experimental results are examined to further refine the current rules for the design of scattering bars. The factors that resolve scattering bars and produce resist artifacts are discussed, including illumination, scattering bar size, type and placement. The results indicate that the existing rules for scattering bar design need to be modified for use in 193nm lithography. |
