Development of a plasma etch process for TaN absorber patterning on EUV masks

Guenther G. Ruhl; Josef Mathuni; Dirk Knobloch; Frank-Michael Kamm; Jenspeter Rau; Florian Letzkus; Reinhard Springer

doi:10.1117/12.504243

28 August 2003 Development of a plasma etch process for TaN absorber patterning on EUV masks

Guenther G. Ruhl, Josef Mathuni, Dirk Knobloch, Frank-Michael Kamm, Jenspeter Rau, Florian Letzkus, Reinhard Springer

Proceedings Volume 5130, Photomask and Next-Generation Lithography Mask Technology X; (2003) https://doi.org/10.1117/12.504243
Event: Photomask and Next Generation Lithography Mask Technology X, 2003, Yokohama, Japan

Abstract

EUV mask technology poses many new challenges on mask manufacturing processes. One crucial manufacturing step is the patterning of the EUV absorber. Although in the first concepts a Chromium film is used as absorber, increasing demands for shrinking feature sizes will run Chromium out of steam. Due to the necessary oxygen content of the chromium etch plasma and the isotropic etch mechanism for chromium an etch bias of several 10 nm occurs. This results in limitations for the minimal feature size, for which reason a new absorber material has to be developed. The most promising candidate is Tantalum Nitride TaN, which in contrast to the isotropic Cr-etch process, gives the possibility of applying a more anisotropic etch utilizing higher ion energies and sidewall passivation. In this work a plasma etch process for TaN masked with positive CAR resist was developed on masks including a SiO₂ buffer layer. Before running the experiments for process characterization, an endpoint detection solution by OES for very small open areas was developed utilizing principal components analysis (PCA). Additionally, an experimental matrix was set up varying bias power, source power and pressure. The DoE experiments were analyzed with respect to etch selectivities, etch bias, etch polymer formation, sidewall angle, iso-dense bias and linearity. After characterisation of the experimental results, optimized process conditions are discussed. We show that this process is capable of resolving feature sizes below 100 nm.

Citation Download Citation

Guenther G. Ruhl, Josef Mathuni, Dirk Knobloch, Frank-Michael Kamm, Jenspeter Rau, Florian Letzkus, and Reinhard Springer "Development of a plasma etch process for TaN absorber patterning on EUV masks", Proc. SPIE 5130, Photomask and Next-Generation Lithography Mask Technology X, (28 August 2003); https://doi.org/10.1117/12.504243

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