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8 March 2016 Study on overlay AEI-ADI shift on contact layer of advanced technology node
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In this paper, we present a study on the overlay (OVL) shift issue in contact (CT) layer aligned to poly-silicon (short as poly) layer (prior layer) in an advanced technology node [1, 2]. We have showed the wafer level OVL AEI-ADI shift (AEI: After Etch Inspection; ADI: After Developing Inspection; AEI-ADI: AEI minus ADI). Within the shot level map, there exists a center-edge difference. The OVL focus subtraction map can well match the OVL AEI-ADI shift map. Investigation into this interesting correlation finally leads to the conclusion of PR tilt. The film stress of the thick hard mask is responsible for the PR tilt. The method of OVL focus subtraction can therefore be a powerful and convenient tool to represent the OVL mark profile. It is also important to take into account the film deposition when investigating OVL AEI-ADI shift.
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Guogui Deng, Jingan Hao, Lihong Xiao, Bin Xing, Yuntao Jiang, Kaiting He, Qiang Zhang, Weiming He, Chang Liu, Yi-Shih Lin, Qiang Wu, and Xuelong Shi "Study on overlay AEI-ADI shift on contact layer of advanced technology node", Proc. SPIE 9778, Metrology, Inspection, and Process Control for Microlithography XXX, 97782C (8 March 2016);


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