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Proceedings Paper

Scanning electron microscopy imaging of ultra-high aspect ratio hole features
Author(s): Aron J. Cepler; Benjamin Bunday; Bradley L Thiel; John S. Villarrubia
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Paper Abstract

In-line, non-destructive process control metrology of high aspect ratio (HAR) holes and trenches has long been a known gap in metrology. Imaging the bottoms of at-node size contact holes in oxide with aspect rations beyond 10:1 has not yet been demonstrated. Nevertheless, holes and trenches of 30:1, 40:1, or even 60:1 will soon enter production, with these etches being applied to various homogeneous and multi-layer stacks of Si and SiO2. The need comes from Moore's Law and increasing functional density on microchips, on which true 3D memory devices will soon be manufactured. These can take many different forms, but a common building block will be these ultra-HAR etched features. In this work, we show experimental results and simulations from the NIST JMONSEL program to assess the feasibility of measuring such features using both conventional low voltage scanning electron microscopy (SEM) and higher beam energies and low vacuum conditions to ameliorate charging. In our measurements, higher voltage SEM did not improve upon conventional critical dimension (CD)-SEM. Simulations suggest the reason is a failure to overcome a negative oxide potential. Although a signal can in principle be detected from the bottom of contact holes in typical imaging conditions in the CD-SEM, it is likely that it will be very small and possibly below the noise floor.

Paper Details

Date Published: 5 April 2012
PDF: 14 pages
Proc. SPIE 8324, Metrology, Inspection, and Process Control for Microlithography XXVI, 83241N (5 April 2012); doi: 10.1117/12.916552
Show Author Affiliations
Aron J. Cepler, SEMATECH (United States)
SUNY/Albany (United States)
Benjamin Bunday, SEMATECH (United States)
Bradley L Thiel, SEMATECH (United States)
SUNY/Albany (United States)
John S. Villarrubia, NIST (United States)

Published in SPIE Proceedings Vol. 8324:
Metrology, Inspection, and Process Control for Microlithography XXVI
Alexander Starikov, Editor(s)

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