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High index immersion lithography is one of the candidates for next generation lithography technology following water immersion lithography. This technology may be most attractive for the industry since it is effective in raising resolution without seriously changing the chip making processes. This motivates us to continue to study further NA expansion although there are many challenges with respect to either high index fluid development or high index lens material development. In this paper, the current status of high index lithography development compared with the industry's requirements is discussed while considering design feasibility.

In order to respond to the constant demand for more productivity in the manufacture of IC devices, higher throughput and higher resolution are fundamental requirements for each new generation of exposure tools. However, meeting both requirements lead to unwanted aberration we refer to as "thermal aberration". In our experience, the problem of the thermal aberrations does not correlated only to the duration of heavy use. It depends very strongly on both the optical settings and the mask patterns, also even on the specific interaction between the two. So, even if using the same illumination settings, there is a possibility to observe different distribution of thermal aberrations. In this paper, we define and investigate various patterns to be used as targets for thermal aberrations compensation. These patterns are identified as the "weak patterns" of the thermal aberration. We assess several cases of thermal aberrations, and show how the optimized compensation for each is determined and then applied on the actual exposure tools.

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