1 January 2004 Developing a viable multilayer coating process for extreme ultraviolet lithography reticles
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Reticle blanks for extreme ultraviolet lithography (EUVL) are fabricated by depositing reflective Mo/Si multilayer films on superpolished substrates. To obtain a reasonable cost of ownership for EUVL, the multilayer films must be nearly defect free, have excellent reflectance/thickness uniformity, and have a high EUV reflectance. Small particle contaminants on the substrate that can nucleate printable Mo/Si phase defects are a serious concern. We develop an ion-beam thin film planarization process for mitigating the effect of small substrate contaminants that relies on enhancing the smoothing capability of Mo/Si multilayer films; we observe that etching of the Si layers in between deposition steps can yield a significant improvement in smoothing. Using this process substrate particles as large as ~50 nm in diameter are smoothed to ~1 nm in height, rendering them harmless. We further develop this process so that it retains these particle-smoothing capabilities while also achieving a high EUV reflectance and excellent uniformity.
Paul B. Mirkarimi, Eberhard Adolf Spiller, Sherry L. Baker, Victor R. Sperry, Daniel Gorman Stearns, Eric M. Gullikson, "Developing a viable multilayer coating process for extreme ultraviolet lithography reticles," Journal of Micro/Nanolithography, MEMS, and MOEMS 3(1), (1 January 2004). https://doi.org/10.1117/1.1631006

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