Printing 130-nm DRAM isolation pattern: Zernike correlation and tool improvement

To meet lithographic requirements for the 130nm generation, the influence of aberrations on printing of various patterns is investigated. This paper shows a process for patterns that are sensitive to coma and three wave. The aberration sensitivities are calculated and the effect on printing experimentally verified. This analysis leads to slight changes in lens adjustment strategy to accommodate the printing of specific DRAM patterns. Additional improvements in materials and surface figures, as well as reduction in process-induced aberrations and associated RMS wave front error, enable the production of tools that are capable of printing the 130nm device generation. The importance of collaboration between makers of lithography tools and their customers cannot be underestimated in finding tool specific limitations. Because of the length of the design cycle of lithography tools it is necessary to perform analysis of device patterns years in advance. The current work also indicates that patterns historically used to determine lens specifications, such as dense and isolated lines, are insufficient to fully determine lens specifications. This paper also outlines techniques that can be used to reduce aberration sensitivities by use of resolution enhancement techniques. This is another area where close interaction between vendor and customer is needed.