Effect of lens aberrations on OPC model accuracy for low k1 lithography process

As reduction of k1 factor continues, it becomes more extensive to apply resolution enhancement techniques(R-ETs) such as phase shift mask(PSM), optical proximity correction(OPC) and off axis illumination(OAI). OPC has been playing a key role to control of pattern printing accuracy and maximize the overlapping process window especially for logic devices. However, RETs, including OPC, tend to increase the sensitivity of printed images to the projection lens aberrations. In order to improve the pattern uniformities and image qualities, lens aberration should be considered as one of the most important factor to OPC modeling. In this paper, we investigated the impact of lens aberration on data set for OPC model generation. The data of projection lens aberrations on exposure tools were extracted by LITEL In-situ Interferometer(ISI) and the sensitivity of CD variation with each lens aberration was simulated by SIGMA-C Solid-E Simulator. Among the lens aberrations, the significant error sources contributing to setting a limit to use one general OPC model with multiple exposure tools were analyzed. Also, the lens aberration specification to use one general OPC model was proposed. By considering the effect and specification of lens aberrations, further improvement of the OPC model accuracy and prevention of device yield loss originated from lens aberrations are expected.