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Tales of scales: how to enable backup process tool qualification for high-end photomasks
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Paper Abstract

Strict reticle critical dimension (CD) control is needed to supply ≤ 20nm wafer technology nodes. In front end lithographic processes for example, precise temperature control in resist baking steps is considered paramount to limiting reticle CD error sources. Additionally, current density during writing and focus are continuously tracked in 50kV e-beam pattern generators (PG) in order to provide stable CD performance. Despite these strict controls (and many others), feedback compensation strategies are increasingly utilized in mask manufacturing to reach < 2nm 3σ CD uniformity (CDU). Such compensations require stable reticle CD signatures which can be problematic when alternate or backup process tools are employed. The AMTC has applied principle component analysis (PCA) to resist CD measurements of 50kV test reticles fabricated with chemically amplified resists (CAR) in order to quantify the resist CDU capabilities of front and backup lithographic process tools. PCA results elucidate significant resist CDU differences between similar lithographic process tools that are considered well matched via CDU 3σ comparisons. The utility of PCA relies on the statistical analysis of large data sets however, reticle CD sampling is typically sparse, on the 10-2 m or centimeter (cm) scale using conventional scanning electron microscopes (CD SEM). Higher CD spatial resolutions can be achieved using advanced inspection tools, which provide CD data on a substantially smaller length scale (10-4 m), thus yielding a considerably larger CD snapshot for front/backup process tool comparisons. Combining PCA analysis with high spatial resolution CD data provides novel insights into the opportunities for tool and process CD capabilities.

Paper Details

Date Published: 29 June 2012
PDF: 12 pages
Proc. SPIE 8441, Photomask and Next-Generation Lithography Mask Technology XIX, 844103 (29 June 2012); doi: 10.1117/12.964671
Show Author Affiliations
G. R. Cantrell, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)
Christian Bürgel, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)
Martin Sczyrba, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)
Jan Heumann, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)
Stefan Meusemann, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)
Clemens Utzny, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)

Published in SPIE Proceedings Vol. 8441:
Photomask and Next-Generation Lithography Mask Technology XIX
Kokoro Kato, Editor(s)

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