Abstract：[Objective] Overlay targets with a small range and requiring extremely high measurement accuracy are used in the lithography system's alignment, exposure, and measurement processes. They are inevitably affected by many errors when performing specialized functions, e.g., line width and design difference, line edge roughness, and target edge effect. This paper conducts a simulation study on the micro diffraction-based overlay target (μDBO) in the condition of wafer stage overlay (WSO), which is commonly used in lithography, based on the design of overlay alignment targets in the field of measurement. Litho-target design simulation software is known to be more advanced than lithographic imaging simulation software, but its license is usually rarer and more expensive. We propose a novel method for simulating lithography target metrology results using lithography imaging simulation software. The method predicts the detected light intensity distribution in the experiment qualitatively and can calculate target performance in metrology.[Methods] This paper compares the similarities between metrology process imaging in the optical method and lithography imaging. In the metrology process imaging simulation, the target, lens, and imaging sensor modules have analogs in the lithography simulation, which are the mask, lens, and aerial image modules. Thus, metrology target patterns can be represented as mask patterns, and the output of an aerial image from lithography simulation software can be analyzed to obtain metrology information. We use WSO-μDBO targets, which have two different critical dimensions and suffer from a heavy marginal effect in experiments. The self-made DrM software in Matlab code with the rigorous couple wave analysis (RCWA) algorithm and the commercial program HyperLith with the finite-difference time-domain algorithm are used as tools to restore the phenomenon in the experiment. Both programs import the illumination patterns of the experimental instruments as well as the structures of WSO-μDBO targets. The Abbe imaging principle in DrM and the Hopkins approximation in HyperLith are used in the simulations. The pupil imaging simulation is applied to analyze the marginal effect on the original targets. In this simulation study, four key performance indicators (KPI) of WSO-μDBO performance are selected as evaluation indices.[Results] The simulation of WSO-μDBO targets showed that:(1) The special phenomenon of bright and dark lines in the experiment can be reproduced in simulation using both tools and algorithms. (2) In the simulation, this method can provide calculated KPI of μDBO targets in simulation. (3) The aerial image generated by this method was closed between both tools but with a relative error of 1% to 5%, resulting in a discrepancy of around 1 nm between the simulated overlay values. (4) This work presented a novel design of WSO-μDBO targets (Edge, Windmill, and Hybrid) with a relative improvement in simulated stack sensitivity(SS) of 202.6% over the original design. As a result, the simulated metrology error of the target was reduced by 50.9% to 1.3%.[Conclusions] The feasibility of our simulation method is verified by comparing simulated and experimental WSO-μDBO images, which can serve as a new simulation research platform for studying metrology targets. This method is also simple and easy to implement, and it has the potential to reduce the software cost investment in marking design during the production process.
[1] CHEN G Q, BAI S F, KENT E R, et al. Process based metrology target design:20160140267A1[P]. 2015-11-13. [2] HINNEN P, WANG V, MARDANPOUR H, et al. Scatterometry-based on-product focus measurement and monitoring[C]//Proceedings of the ASMC 2013 SEMI Advanced Semiconductor Manufacturing Conference. Saratoga Springs, United States:IEEE, 2013:352-359. [3] SMILDE H J H, VAN HAREN R J F, VAN BUËL W, et al. Target design optimization for overlay scatterometry to improve on-product overlay[C]//Proceedings of SPIE 9424, Metrology, Inspection, and Process Control for Microlithography XXIX. San Jose, United States:SPIE, 2015:355-364. [4] VAN BUEL H W M, BELTMAN J M M, LIU X L, et al. Optimization of target arrangement and associated target:10331043B2[P]. 2015-01-29. [5] 韦亚一.超大规模集成电路先进光刻理论与应用[M].北京:科学出版社, 2016. WEI Y Y. Super frontier advanced lithography theory and application[M]. Beijing:Science Press, 2016.(in Chinese) [6] DETTONI F, BOUYSSOU R, DEZAUZIER C, et al. Enhanced 28 nm FD-SOI diffraction based overlay metrology based on holistic metrology qualification[C]//Proceedings of SPIE 10145, Metrology, Inspection, and Process Control for Microlithography XXXI. San Jose, United States:SPIE, 2017:680-690. [7] ASML NETHERLANDS B V. ASML's customer magazine, D4C function[OL].(2017-06-30)[2022-10-15] . https://max.book118.com/html/2017/0629/119064096.shtm. [8] BATISTAKIS C, MIDDLEBROOKS S A, WUISTER S F. Systems and methods for predicting layer deformation:2020320238A1[P]. 2020-10-08. [9] LERAY P, JEHOUL C, SOCHA R, et al. Improving scanner wafer alignment performance by target optimization[C]//Proceedings of SPIE 9778, Metrology, Inspection, and Process Control for Microlithography XXX. San Jose, United States:SPIE, 2016:827-833. [10] MENCHTCHIKOV B, SOCHA R, RAGHUNATHAN S, et al. Computational scanner wafer mark alignment[C]//Proceedings of SPIE 10147, Optical Microlithography XXX. San Jose, United States:SPIE, 2017:399-407. [11] 毛晓明.先进节点工艺的新型套刻误差测量系统[D].上海:上海交通大学, 2019. MAO X M. New overlay metrology system of advanced node process[D]. Shanghai:Shanghai Jiaotong University, 2019.(in Chinese) [12] BLANCQUAERT Y, DEZAUZIER C, DEPRE J, et al. Performance of ASML yieldstar μDBO overlay targets for advanced lithography nodes C028 and C014 overlay process control[C]//Proceedings of SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII. San Jose, United States:SPIE, 2013:424-436. [13] Panoramic Technology Inc. Lithography simulator[Z/OL].(2022-06-18)[2022-10-15]. https://www.panoramictech.com/index.php?option=com_content&view=article&id=11&Itemid=7. [14] 陈德伟.衍射光学中的严格耦合波分析方法[D].合肥:中国科学技术大学, 2004. CHEN D W. Rigorous coupled wave analysis method in diffractive optics[D]. Hefei:University of Science and Technology of China, 2004.(in Chinese) [15] ERDMANN A, EVANSCHITZKY P, CITARELLA G, et al. Rigorous mask modeling using waveguide and FDTD methods:An assessment for typical Hyper-NA imaging problems[C]//Proceedings of SPIE 6283, Photomask and Next-Generation Lithography Mask Technology XIII. Yokohama, Japan:SPIE, 2006:338-348. [16] DEN BOEF A J. Optical wafer metrology sensors for process-robust CD and overlay control in semiconductor device manufacturing[J]. Surface Topography:Metrology and Properties, 2016, 4(2):023001. [17] DIRAWI R, KATZ S, VOLKOVICH R. Process variation impacts on optical overlay accuracy signature[C]//Proceedings of SPIE 11611, Metrology, Inspection, and Process Control for Semiconductor Manufacturing XXXV. Bellingham, Washington, United States:SPIE, 2021:685-698. [18] MACK C. Fundamental principles of optical lithography:The science of microfabrication[M]. Chichester:John Wiley&Sons, 2007. [19] ZHANG L B, FENG Y B, DONG L S, et al. New alignment mark design structures for higher diffraction order wafer quality enhancement[C]//Proceedings of SPIE 10145, Metrology, Inspection, and Process Control for Microlithography XXXI. San Jose, United States:SPIE, 2017:691-698.
2023, Vol. 63 
