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Proceedings Paper

Advanced in-line metrology strategy for self-aligned quadruple patterning
Author(s): Robin Chao; Mary Breton; Benoit L'herron; Brock Mendoza; Raja Muthinti; Florence Nelson; Abraham De La Pena; Fee li Le; Eric Miller; Stuart Sieg; James Demarest; Peter Gin; Matthew Wormington; Aron Cepler; Cornel Bozdog; Matthew Sendelbach; Shay Wolfling; Tom Cardinal; Sivananda Kanakasabapathy; John Gaudiello; Nelson Felix
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Paper Abstract

Self-Aligned Quadruple Patterning (SAQP) is a promising technique extending the 193-nm lithography to manufacture structures that are 20nm half pitch or smaller. This process adopts multiple sidewall spacer image transfers to split a rather relaxed design into a quarter of its original pitch. Due to the number of multiple process steps required for the pitch splitting in SAQP, the process error propagates through each deposition and etch, and accumulates at the final step into structure variations, such as pitch walk and poor critical dimension uniformity (CDU). They can further affect the downstream processes and lower the yield. The impact of this error propagation becomes significant for advanced technology nodes when the process specifications of device design CD requirements are at nanometer scale. Therefore, semiconductor manufacturing demands strict in-line process control to ensure a high process yield and improved performance, which must rely on precise measurements to enable corrective actions and quick decision making for process development. This work aims to provide a comprehensive metrology solution for SAQP.

During SAQP process development, the challenges in conventional in-line metrology techniques start to surface. For instance, critical-dimension scanning electron microscopy (CDSEM) is commonly the first choice for CD and pitch variation control. However, it is found that the high aspect ratio at mandrel level processes and the trench variations after etch prevent the tool from extracting the true bottom edges of the structure in order to report the position shift. On the other hand, while the complex shape and variations can be captured with scatterometry, or optical CD (OCD), the asymmetric features, such as pitch walk, show low sensitivity with strong correlations in scatterometry. X-ray diffraction (XRD) is known to provide useful direct measurements of the pitch walk in crystalline arrays, yet the data analysis is influenced by the incoming geometry and must be used carefully.

A successful implementation of SAQP process control for yield improvement requires the metrology issues to be addressed. By optimizing the measurement parameters and beam configurations, CDSEM measurements distinguish each of the spaces corresponding to the upstream mandrel processes and report their CDs separately to feed back to the process team for the next development cycle. We also utilize the unique capability in scatterometry to measure the structure details in-line and implement a “predictive” process control, which shows a good correlation between the “predictive” measurement and the cross-sections from our design of experiments (DOE). The ability to measure the pitch walk in scatterometry was also demonstrated. This work also explored the frontier of in-line XRD capability by enabling an automatic RSM fitting on tool to output pitch walk values. With these advances in metrology development, we are able to demonstrate the impacts of in-line monitoring in the SAQP process, to shorten the patterning development learning cycle to improve the yield.

Paper Details

Date Published: 30 March 2016
PDF: 10 pages
Proc. SPIE 9778, Metrology, Inspection, and Process Control for Microlithography XXX, 977813 (30 March 2016); doi: 10.1117/12.2220601
Show Author Affiliations
Robin Chao, IBM Albany NanoTech (United States)
Mary Breton, IBM Albany NanoTech (United States)
Benoit L'herron, IBM Albany NanoTech (United States)
Brock Mendoza, IBM Albany NanoTech (United States)
Raja Muthinti, IBM Albany NanoTech (United States)
Florence Nelson, IBM Albany NanoTech (United States)
Abraham De La Pena, IBM Albany NanoTech (United States)
Fee li Le, IBM Albany NanoTech (United States)
Eric Miller, IBM Albany NanoTech (United States)
Stuart Sieg, IBM Albany NanoTech (United States)
James Demarest, IBM Albany NanoTech (United States)
Peter Gin, Bruker, Inc. (United States)
Matthew Wormington, Bruker, Inc. (United States)
Aron Cepler, Nova Measuring Instruments, Inc. (United States)
Cornel Bozdog, ReVera (United States)
Matthew Sendelbach, Nova Measuring Instruments, Inc. (United States)
Shay Wolfling, Nova Measuring Instruments, LTD (Israel)
Tom Cardinal, IBM Albany NanoTech (United States)
Sivananda Kanakasabapathy, IBM Albany NanoTech (United States)
John Gaudiello, IBM Albany NanoTech (United States)
Nelson Felix, IBM Albany NanoTech (United States)

Published in SPIE Proceedings Vol. 9778:
Metrology, Inspection, and Process Control for Microlithography XXX
Martha I. Sanchez, Editor(s)

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