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Proceedings Paper

Electrical test prediction using hybrid metrology and machine learning
Author(s): Mary Breton; Robin Chao; Gangadhara Raja Muthinti; Abraham A. de la Peña; Jacques Simon; Aron J. Cepler; Matthew Sendelbach; John Gaudiello; Susan Emans; Michael Shifrin; Yoav Etzioni; Ronen Urenski; Wei Ti Lee
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Paper Abstract

Electrical test measurement in the back-end of line (BEOL) is crucial for wafer and die sorting as well as comparing intended process splits. Any in-line, nondestructive technique in the process flow to accurately predict these measurements can significantly improve mean-time-to-detect (MTTD) of defects and improve cycle times for yield and process learning. Measuring after BEOL metallization is commonly done for process control and learning, particularly with scatterometry (also called OCD (Optical Critical Dimension)), which can solve for multiple profile parameters such as metal line height or sidewall angle and does so within patterned regions. This gives scatterometry an advantage over inline microscopy-based techniques, which provide top-down information, since such techniques can be insensitive to sidewall variations hidden under the metal fill of the trench. But when faced with correlation to electrical test measurements that are specific to the BEOL processing, both techniques face the additional challenge of sampling. Microscopy-based techniques are sampling-limited by their small probe size, while scatterometry is traditionally limited (for microprocessors) to scribe targets that mimic device ground rules but are not necessarily designed to be electrically testable. A solution to this sampling challenge lies in a fast reference-based machine learning capability that allows for OCD measurement directly of the electrically-testable structures, even when they are not OCD-compatible. By incorporating such direct OCD measurements, correlation to, and therefore prediction of, resistance of BEOL electrical test structures is significantly improved. Improvements in prediction capability for multiple types of in-die electrically-testable device structures is demonstrated. To further improve the quality of the prediction of the electrical resistance measurements, hybrid metrology using the OCD measurements as well as X-ray metrology (XRF) is used. Hybrid metrology is the practice of combining information from multiple sources in order to enable or improve the measurement of one or more critical parameters. Here, the XRF measurements are used to detect subtle changes in barrier layer composition and thickness that can have second-order effects on the electrical resistance of the test structures. By accounting for such effects with the aid of the X-ray-based measurements, further improvement in the OCD correlation to electrical test measurements is achieved. Using both types of solution incorporation of fast reference-based machine learning on nonOCD-compatible test structures, and hybrid metrology combining OCD with XRF technology improvement in BEOL cycle time learning could be accomplished through improved prediction capability.

Paper Details

Date Published: 12 April 2017
PDF: 8 pages
Proc. SPIE 10145, Metrology, Inspection, and Process Control for Microlithography XXXI, 1014504 (12 April 2017); doi: 10.1117/12.2261091
Show Author Affiliations
Mary Breton, IBM Corp. (United States)
Robin Chao, IBM Corp. (United States)
Gangadhara Raja Muthinti, IBM Corp. (United States)
Abraham A. de la Peña, IBM Corp. (United States)
Jacques Simon, IBM Corp. (United States)
Aron J. Cepler, Nova Measuring Instruments, Inc. (United States)
Matthew Sendelbach, Nova Measuring Instruments Inc. (United States)
John Gaudiello, IBM Corp. (United States)
Susan Emans, Nova Measuring Instruments Inc. (United States)
Michael Shifrin, Nova Measuring Instruments Ltd. (Israel)
Yoav Etzioni, Nova Measuring Instruments Ltd. (Israel)
Ronen Urenski, Nova Measuring Instruments Ltd. (Israel)
Wei Ti Lee, ReVera, a Nova Co. (United States)

Published in SPIE Proceedings Vol. 10145:
Metrology, Inspection, and Process Control for Microlithography XXXI
Martha I. Sanchez, Editor(s)

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