Carbon nanotube metrology in a CD SEM

Colin Yates; Thomas Rueckes; Richard J. Carter

doi:10.1117/12.712352

5 April 2007 Carbon nanotube metrology in a CD SEM

Colin Yates, Thomas Rueckes, Richard J. Carter

Proceedings Volume 6518, Metrology, Inspection, and Process Control for Microlithography XXI; 65180N (2007) https://doi.org/10.1117/12.712352
Event: SPIE Advanced Lithography, 2007, San Jose, California, United States

Abstract

In the Nantero NRAM process, a carbon nanotube film is patterned using conventional photolithography and etch techniques. CD SEM metrology of the printed resist image is straightforward. However, challenges arise when SEM inspecting an etched nanotube pattern. Under conventional SEM inspection, a nanotube pattern is nearly invisible. In order to facilitate nanotube pattern characterization, metrology structures have been developed which use passive voltage contrast to cause electron emission from the nanotube pattern and associated conducting structures. These enable manual inspection of the nanotubes, along with automated pattern recognition and automated CD measurement. The voltage contrast is achieved by connecting the nanotubes to a remote "charge-sink" outside the image field consisting of a large rectangle of metal. The voltage contrast occurs with no extra electrical connection to the wafer, and without special SEM components or beam adjustment. The metrology structures are used in two general ways: 1. Nanotubes are clearly imaged, enabling inspection, CD measurement, coat-quality characterization, etc. 2. Indicator structures in associated process layers light up when contacted by nanotubes, enabling measurements of line-end shortening; etch bias; overlay; etc. Various structures have been developed: 1. CD cells for manual and automated CD measurement. 2. Vernier structures for characterization of overlay, line-end shortening and etch-bias. 3. Serpentine structures for characterization of nanotube coat quality using conduction length.

Citation Download Citation

Colin Yates, Thomas Rueckes, and Richard J. Carter "Carbon nanotube metrology in a CD SEM", Proc. SPIE 6518, Metrology, Inspection, and Process Control for Microlithography XXI, 65180N (5 April 2007); https://doi.org/10.1117/12.712352

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KEYWORDS

Scanning electron microscopy

Metals

Metrology

Carbon nanotubes

Inspection

Etching

Semiconducting wafers

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