1 September 2017 Investigation of alternative absorbers for extreme ultraviolet mask blanks
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Abstract
Mask three-dimensional (3D) effects in extreme ultraviolet (EUV) lithography critically influence pattern transfer such as horizontal-vertical bias and/or CD shift. Although the mask 3D effects can be reduced using a thin film absorber, the current Ta-based absorber reaches its thin film limit at <60  nm for both binary and phase-shift type usages. To improve mask 3D effects for future EUV lithography production, the absorber material and film stack should be reconsidered. We investigated two types of thin film structure as a binary type absorber. One is a high-k type absorber. We selected nickel which has been proposed as one of the thin absorber solutions. Nickel enables less than 2% peak reflectivity at 30-nm thickness due to its high absorption. The other is a multilayer (ML)-type absorber. This type of absorber cancels out reflection from each interface, and thus low reflectivity is achieved. In the case of Ta/Si ML absorber, ≤2% reflectivity can be expected at the 39-nm film thickness.
© 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
Yohei Ikebe, Hirofumi Kozakai, Tsutomu Shoki, Takahiro Onoue, "Investigation of alternative absorbers for extreme ultraviolet mask blanks," Journal of Micro/Nanolithography, MEMS, and MOEMS 16(4), 041006 (1 September 2017). https://doi.org/10.1117/1.JMM.16.4.041006 . Submission: Received: 16 May 2017; Accepted: 24 July 2017
Received: 16 May 2017; Accepted: 24 July 2017; Published: 1 September 2017
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