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Effects of hard mask etch on final topography of advanced phase shift masks
Author(s): Olga Hortenbach; Haiko Rolff; Alexander Lajn; Martin Baessler
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Paper Abstract

Continuous shrinking of the semiconductor device dimensions demands steady improvements of the lithographic resolution on wafer level. These requirements challenge the photomask industry to further improve the mask quality in all relevant printing characteristics. In this paper topography of the Phase Shift Masks (PSM) was investigated. Effects of hard mask etch on phase shift uniformity and mask absorber profile were studied. Design of experiments method (DoE) was used for the process optimization, whereas gas composition, bias power of the hard mask main etch and bias power of the over-etch were varied. In addition, influence of the over-etch time was examined at the end of the experiment. Absorber depth uniformity, sidewall angle (SWA), reactive ion etch lag (RIE lag) and through pitch (TP) dependence were analyzed. Measurements were performed by means of Atomic-force microscopy (AFM) using critical dimension (CD) mode with a boot-shaped tip. Scanning electron microscope (SEM) cross-section images were prepared to verify the profile quality. Finally CD analysis was performed to confirm the optimal etch conditions. Significant dependence of the absorber SWA on hard mask (HM) etch conditions was observed revealing an improvement potential for the mask absorber profile. It was found that hard mask etch can leave a depth footprint in the absorber layer. Thus, the etch depth uniformity of hard mask etch is crucial for achieving a uniform phase shift over the active mask area. The optimized hard mask etch process results in significantly improved mask topography without deterioration of tight CD specifications.

Paper Details

Date Published: 13 July 2017
PDF: 8 pages
Proc. SPIE 10454, Photomask Japan 2017: XXIV Symposium on Photomask and Next-Generation Lithography Mask Technology, 104540K (13 July 2017); doi: 10.1117/12.2277708
Show Author Affiliations
Olga Hortenbach, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)
Haiko Rolff, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)
Alexander Lajn, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)
Martin Baessler, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)


Published in SPIE Proceedings Vol. 10454:
Photomask Japan 2017: XXIV Symposium on Photomask and Next-Generation Lithography Mask Technology
Kiwamu Takehisa, Editor(s)

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