While the mainstream wafer production is at 0.065 and 0.045 um with 300 mm diameter wafers with ArF exposure tools systems, an idea to explore production feasibility under groundrules smaller than 0.09 um while maintain the cost advantages in KrF exposure tools systems becomes more and more popular and important to all companies including 300mm/200mm FAB. But the k1 factor for sub 0.09um with current popular KrF exposure tools will be about 0.31, which has the same level of complexity in optical proximity correction compared to 0.045 um at 0.93 NA with 193 nm exposure tools. Several RET (Resolution Enhancement Technology) techniques have been proposed for low k1 case and some good results have been achieved. However, each RET techniques has their own merits and demerits. It is still attractive to find out a solution with current KrF exposure tools, popular illumination settings and cost effective masks. In this paper, we will introduce our study for sub 0.09 um design rule with maximum 0.82NA KrF scanner tools. No special RET techniques are used and acceptable DOF, EL, MEEF, LWR and CD proximity are achieved. A novel photoresist optimization solution is both discussed.

For low k1 lithography process, some minor facotrs' impacts are strongly enhanced such as MEEF, lens distortion, wafer topography, pattern density and so on. How to minimize those impacts becomes more and more important. Unfortunately those impacts are not controlled by lithography process itself and caused by other modules such as layout design, integration schemes, mask making, film deposition, CMP and so on. A method to reduce those impacts is quietly needed. DFM (Design for Manufacturability) is a popular and effective approach to get more robust process by reducing pattern loading effect. In this paper, we will show our study on wafer local topography in low k1 lithography process. Products with sub-90nm design rules and different device structures are processed by pure KrF process. The maximum 0.82NA KrF scanner tools are used. The k1 factor is low enough to enhance the impacts. By using DFM solutions, we had resolved these issues and the process window are obviously improved.