Ruthenium (Ru) peeling and predicting robustness of the capping layer using finite element method (FEM) modeling

Il-Yong Jang; Arun John; Frank Goodwin; Su-Young Lee; Byung-Gook Kim; Seong-Sue Kim; Chan-Uk Jeon; Jae Hyung Kim; Yong Hoon Jang

doi:10.1117/12.2069991

28 July 2014 Ruthenium (Ru) peeling and predicting robustness of the capping layer using finite element method (FEM) modeling

Il-Yong Jang, Arun John, Frank Goodwin, Su-Young Lee, Byung-Gook Kim, Seong-Sue Kim, Chan-Uk Jeon, Jae Hyung Kim, Yong Hoon Jang

Author Affiliations +

Proceedings Volume 9256, Photomask and Next-Generation Lithography Mask Technology XXI; 92560I (2014) https://doi.org/10.1117/12.2069991
Event: Photomask Japan 2014, 2014, Yokohama, Japan

Abstract

Ruthenium (Ru) film used as capping layer in extreme ultraviolet (EUV) mask peeled off after annealing and in-situ UV (IUV) cleaning. We investigated Ru peeling and found out that the mechanical stress caused by the formation of Si oxide due to the penetration of oxygen atoms from ambient or cleaning media to top-Si of ML is the root cause for the problem. To support our experimental results, we developed a numerical model of finite element method (FEM) using commercial software (ABAQUS™) to calculate the stress and displacement forced on the capping layer. By using this model, we could observe that the displacement agrees well with the actual results measured from the transmission electron microscopy (TEM) image. Using the ion beam deposition (IBD) tool at SEMATECH, we developed four new types of alternative capping materials (RuA, RuB, B₄C, B₄C-buffered Ru). The durability of each new alternative capping layer observed by experiment was better than that of conventional Ru. The stress and displacement calculated from each new alternative capping layer, using modeling, also agreed well with the experimental results. A new EUV mask structure is proposed, inserting a layer of B₄C (B₄C-buffered Ru) at the interface between the capping layer (Ru) and the top-Si layer. The modeling results showed that the maximum displacement and bending stress observed from the B₄C-buffered Ru are significantly lower than that of single capping layer cases. The durability investigated from the experiment also showed that the B₄C-buffered structure is at least 3X stronger than that of conventional Ru.

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Il-Yong Jang, Arun John, Frank Goodwin, Su-Young Lee, Byung-Gook Kim, Seong-Sue Kim, Chan-Uk Jeon, Jae Hyung Kim, and Yong Hoon Jang "Ruthenium (Ru) peeling and predicting robustness of the capping layer using finite element method (FEM) modeling", Proc. SPIE 9256, Photomask and Next-Generation Lithography Mask Technology XXI, 92560I (28 July 2014); https://doi.org/10.1117/12.2069991

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