Amid continuing reduction in average wafer sale price, in the past 30 years, the industry witnesses continuous shrink in production design rules in order to gain performance per unit area on each silicon wafer. While the mainstream wafer production is at 65 and 45 nm with 300 mm diameter wafers, to maintain cost competitiveness, 200 mm wafer companies also start to explore production feasibility under groundrules smaller than 110 nm while maintain the cost advantages in KrF exposure tools systems. The k1 factor under 110 nm with 248 nm illumination will be below 0.35. For example, at 90 nm, at 0.80 NA, the k1 factor is 0.29, which owns the same level of complexity in optical proximity correction compared to 65 nm at 0.93 NA with 193 nm exposure tools. However, due to that the KrF photoresists are originally designed for ground rules greater than 110 nm, such as, 130 nm structures, it is relatively unknown how feasible it is to extend their performance below 110 nm. In this paper, we will show our initial study in CD process window and CD through pitch performance at 90 nm groundrule for 3 critical layers - Active, Gate poly and Contact. The wafer data in process window and optical proximity will be analyzed and compared with performance specifications of the current exposure tools.
To maintain cost competitiveness for the 200 mm wafer production, the industry starts to explore production feasibility under groundrules smaller than 110 nm while maintaining the cost advantages given by the KrF exposure tools systems. The k1 factor under 110 nm will be below 0.35. It has the similar level of complexity in optical proximity correction compared to 65 nm at 0.93 NA with 193 nm exposure tools. However, due to that the KrF photoresists are originally designed for ground rules greater than 110 nm it is relatively unknown how feasible it is to extend their performance below 110 nm. As we know, in each photoresist design, there is a balance among three major performance indices, which are spatial resolution, photospeed, and pattern edge roughness. For example, a fast photoresist may not have the same resolution or pattern edge roughness performance as a slow photoresist, which may, of course, has low productivity. A good production resist usually has a good balance of all three parameters. This paper will explore the line edge roughness parameters under sub 110 nm design rules and will explore the performance dependence on imaging conditions. Classical photo process optimization result is shown and acceptable LWR performance is achieved. In addition, a comparison in line edge roughness among 3 production KrF photoresists will be made.
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