17 April 2014 Prospects of DUV OoB suppression techniques in EUV lithography
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Abstract
Though scaling of source power is still the biggest challenge in EUV lithography (EUVL) technology era, CD and overlay controls for transistor‟s requirement are also precondition of adopting EUVL in mass production. Two kinds of contributors are identified as risks for CDU and Overlay: Infrared (IR) and deep ultraviolet (DUV) out of band (OOB) radiations from laser produced plasma (LPP) EUV source. IR from plasma generating CO2 laser that causes optics heating and wafer overlay error is well suppressed by introducing grating on collector to diffract IR off the optical axis and is the effect has been confirmed by operation of pre-production tool (NXE3100). EUV and DUV OOB which are reflected from mask black boarder (BB) are root causes of EUV-specific CD error at the boundaries of exposed shots which would result in the problem of CDU out of spec unless sufficiently suppressed. Therefore, control of DUV OOB reflection from the mask BB is one of the key technologies that must be developed prior to EUV mass production. In this paper, quantitative assessment on the advantage and the disadvantage of potential OOB solutions will be discussed. EUV and DUV OOB impacts on wafer CDs are measured from NXE3100 & NXE3300 experiments. Significant increase of DUV OOB impact on CD from NXE3300 compared with NXE3100 is observed. There are three ways of technology being developed to suppress DUV OOB: spectral purity filter (SPF) as a scanner solution, multi-layer etching as a solution on mask, and resist top-coating as a process solution. PROs and CONs of on-scanner, on-mask, and on-resist solution for the mass production of EUV lithography will be discussed.
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Chang-Min Park, Insung Kim, Sang-Hyun Kim, Dong-Wan Kim, Myung-Soo Hwang, Soon-Nam Kang, Cheolhong Park, Hyun-Woo Kim, Jeong-Ho Yeo, Seong-Sue Kim, "Prospects of DUV OoB suppression techniques in EUV lithography", Proc. SPIE 9048, Extreme Ultraviolet (EUV) Lithography V, 90480S (17 April 2014); doi: 10.1117/12.2046132; https://doi.org/10.1117/12.2046132
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