11 May 2009 An evaluation of a new side-wall-angle measurement technique for mask patterns by CD-SEM
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Proceedings Volume 7379, Photomask and Next-Generation Lithography Mask Technology XVI; 737922 (2009); doi: 10.1117/12.824280
Event: Photomask and NGL Mask Technology XVI, 2009, Yokohama, Japan
Abstract
The verification of not only two-dimensional feature but also three-dimensional feature, sidewall angle (SWA), has been becoming increasingly important in NGL mask fabrication. The OMOG (Opaque MoSi on Glass) mask for ArF immersion lithography with double patterning and the reflective type mask for EUV (Extreme Ultra- Violet) lithography are especially in need of it. There are several metrology tools e.g. SEM, AFM, and Scatterometry for sidewall angle (SWA) measurement. We evaluated a new SWA measurement method using white-band width (WBW), which is equivalent to mask pattern edge width, by CD-SEM. In general, WBW correlates with SWA. It narrows as SWA becomes steeper. However, the correlation deteriorates when SWA is vertically near. This is due to the resolution limit of electron beam diameter used for measurement. We analyzed the new approach to measure SWA by CD-SEM to solve this problem. And the analysis revealed that WBW changes proportionately electron beam current value. The amount of width change depends on SWA. In this paper, we will describe the new SWA measurement method and its evaluation results as well as SWA measurement results of OMOG and EUV masks.
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Hidemitsu Hakii, Isao Yonekura, Masashi Kawashita, Yosuke Kojima, Yoshifumi Sakamoto, Keishi Tanaka, "An evaluation of a new side-wall-angle measurement technique for mask patterns by CD-SEM", Proc. SPIE 7379, Photomask and Next-Generation Lithography Mask Technology XVI, 737922 (11 May 2009); doi: 10.1117/12.824280; https://doi.org/10.1117/12.824280
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KEYWORDS
Photomasks

Extreme ultraviolet

Scanning electron microscopy

Metrology

Pixel resolution

Time metrology

3D metrology

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