0.33 NA EUV lithography is expected to be introduced into High Volume Manufacturing at k 1 values of approximately 0.4...0.5. This is significantly larger than state of the art immersion lithography which can operate at k 1 of 0.3. We investigated the impact of contrast enhancement on the imaging properties of Contact Holes and Lines and Spaces. Contrast was adjusted by changing the illumination properties pupil fill ratio and center incidence angle. We found a strong improvement of the local Critical Dimension control: line width variation for Lines and Spaces and hole to hole CD variations for arrays of contact holes. For all features we found a similar dependency on contrast. As the local Critical Dimension variations contribute significant to Edge Placement Error budgets, we foresee the implementation of contrast enhancements already at moderate k 1 values around 0.4.
With the introduction of the NXE:3100 NA=0.25 exposure system a big step has been made to get EUV lithography ready for High Volume Manufacturing. Over the last year, 6 exposure systems have been shipped to various customers around the world, active in Logic, DRAM, MPU and Flash memory, covering all major segments in the semi-conductor industry. The integration and qualification of these systems have provided a great learning, identifying the benefits of EUV over ArF immersion and the critical parameters of the exposure tool and how to operate it.In this paper we will focus specifically on the imaging performance of the NXE:3100 EUV scanner. Having been operational for more than a year a wide range of features were evaluated for lithographic performance across the field and across wafer. CD results of 32nm contact holes, 27nm isolated and dense lines, 27nm two-bar, 22nm dense L/S with Dipole, as well as several device features will be discussed and benchmarked against the current ArF immersion performance. A budget verification will be presented showing CD and contrast budgets for a selection of lithographic features. The contribution of the resist process and the mask will be discussed as well.The litho performance optimization will be highlighted with the 27nm twobar and isolated lines features that are sensitive to the illuminator pupil shape and projection lens aberrations.We will estimate the amount of resist induced contrast loss for 27 and 22nm L/S based on measurements of Exposure Latitude and the contributors from the exposure system.We will further present on the impact of variations in the mask blank and patterned mask on imaging, with several new contributors to take into account compared to traditional transmission masks.Finally, the combined results will be projected to the NXE:3300 NA=0.33 exposure system to give an outlook for its imaging performance capabilities.
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