18 October 2017 Advanced photomask chrome etch: selectivity without sacrifice
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Abstract
The current Cr etch solutions will need to be improved to keep up with market demand for smaller features and reticle resolution while the industry awaits the maturity of EUV technology, and based on the current roadmap, there is an urgency to improve the Cr reticle pattern resolution capability today. That resolution capability comes in the form of writing smaller features on a photomask, but as the Cr-to-photoresist (PR) ratio increases beyond three to one, there is a negative impact on the integrity of the PR, resulting in costly product scrap. Thinner PR layers are required to avoid such scrap, since the Cr layer is fixed. This necessitates lower consumption of the PR during the etch process, and that translates to higher etch selectivity of Cr to PR. This manuscript covers the ideas selected to address reduction in PR loss, the experiments around a few of those ideas, and the results of those experiments. Our experimental set shows that a <25% increase in selectivity and a 40-50% reduction in over-etch can be achieved through increased ion/neutral control during the etch process. This, combined with resist pretreatments or other Cr etch modifications, could prove to be a solution in the interim, but while the initial results are promising, further investigation is needed on production nodes to realize the full impact of this achievement.
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Michael Morgan, Michael Morgan, Chris Johnson, Chris Johnson, Kristen Bevlin, Kristen Bevlin, Dwarakanath Geerpuram, Dwarakanath Geerpuram, Russ Westerman, Russ Westerman, } "Advanced photomask chrome etch: selectivity without sacrifice", Proc. SPIE 10451, Photomask Technology, 1045115 (18 October 2017); doi: 10.1117/12.2281439; https://doi.org/10.1117/12.2281439
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