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Proceedings Paper

Metrology of deep trench etched memory structures using 3D scatterometry
Author(s): Peter Reinig; Rene Dost; Manfred Moert; Thomas Hingst; Ulrich Mantz; Jasen Moffitt; Sushil Shakya; Christopher J. Raymond; Mike Littau
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Paper Abstract

Scatterometry is receiving considerable attention as an emerging optical metrology in the silicon industry. One area of progress in deploying these powerful measurements in process control is performing measurements on real device structures, as opposed to limiting scatterometry measurements to periodic structures, such as line-space gratings, placed in the wafer scribe. In this work we will discuss applications of 3D scatterometry to the measurement of advanced trench memory devices. This is a challenging and complex scatterometry application that requires exceptionally high-performance computational abilities. In order to represent the physical device, the relatively tall structures require a high number of slices in the rigorous coupled wave analysis (RCWA) theoretical model. This is complicated further by the presence of an amorphous silicon hard mask on the surface, which is highly sensitive to reflectance scattering and therefore needs to be modeled in detail. The overall structure is comprised of several layers, with the trenches presenting a complex bow-shape sidewall that must be measured. Finally, the double periodicity in the structures demands significantly greater computational capabilities. Our results demonstrate that angular scatterometry is sensitive to the key parameters of interest. The influence of further model parameters and parameter cross correlations have to be carefully taken into account. Profile results obtained by non-library optimization methods compare favorably with cross-section SEM images. Generating a model library suitable for process control, which is preferred for precision, presents numerical throughput challenges. Details will be discussed regarding library generation approaches and strategies for reducing the numerical overhead. Scatterometry and SEM results will be compared, leading to conclusions about the feasibility of this advanced application.

Paper Details

Date Published: 10 May 2005
PDF: 11 pages
Proc. SPIE 5752, Metrology, Inspection, and Process Control for Microlithography XIX, (10 May 2005); doi: 10.1117/12.599342
Show Author Affiliations
Peter Reinig, Infineon Technologies Dresden (Germany)
Rene Dost, Infineon Technologies Dresden (Germany)
Manfred Moert, Infineon Technologies Dresden (Germany)
Thomas Hingst, Infineon Technologies Dresden (Germany)
Ulrich Mantz, Infineon Technologies Dresden (Germany)
Jasen Moffitt, Infineon Technologies Richmond (United States)
Sushil Shakya, Infineon Technologies Richmond (United States)
Christopher J. Raymond, Accent Optical Technologies (United States)
Mike Littau, Accent Optical Technologies (United States)

Published in SPIE Proceedings Vol. 5752:
Metrology, Inspection, and Process Control for Microlithography XIX
Richard M. Silver, Editor(s)

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