9 July 2015 Alternative EUV mask technology to compensate for mask 3D effects
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Traditional EUV masks, with absorber on top of the multi-layer (ML) mirror, generally suffer from mask 3D effects: H/V shadowing, best focus shifts through pitch and pattern shifts through focus. These effects reduce the overlapping process window, complicate optical proximity correction and generate overlay errors. With further pitch scaling, these mask 3D effects are expected to become stronger, increasing the need for a compensation strategy. In this study, we have proven by simulations and experiments that alternative mask technologies can lower mask 3D effects and therefore have the potential to improve the imaging of critical EUV layers. We have performed an experimental imaging study of a prototype Etched ML mask, which has recently become available. This prototype alternative mask has only half the ML mirror thickness (20 Mo/Si pairs) and contains no absorber material at all. Instead, the ML mirror is etched away to the substrate at the location of the dark features. For this Etched ML mask, we have compared the imaging performance for mask 3D related effects to that of a standard EUV mask, using wafer exposures at 0.33 NA. Experimental data are compared to the simulated predictions and the benefits and drawbacks of such an alternative mask are shown. Besides the imaging performance, we will also discuss the manufacturability challenges related to the etched ML mask technology.
© (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Lieve Van Look, Lieve Van Look, Vicky Philipsen, Vicky Philipsen, Eric Hendrickx, Eric Hendrickx, Geert Vandenberghe, Geert Vandenberghe, Natalia Davydova, Natalia Davydova, Friso Wittebrood, Friso Wittebrood, Robert de Kruif, Robert de Kruif, Anton van Oosten, Anton van Oosten, Junji Miyazaki, Junji Miyazaki, Timon Fliervoet, Timon Fliervoet, Jan van Schoot, Jan van Schoot, Jens Timo Neumann, Jens Timo Neumann, } "Alternative EUV mask technology to compensate for mask 3D effects ", Proc. SPIE 9658, Photomask Japan 2015: Photomask and Next-Generation Lithography Mask Technology XXII, 96580I (9 July 2015); doi: 10.1117/12.2197213; https://doi.org/10.1117/12.2197213

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