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Evaluation of Carbon Nanotube Probes in Critical Dimension Atomic Force Microscopes



Jinho Choi, Byong Chon Park, Sang Jung Ahn, Dal-Hyun Kim, J Lyou, Ronald G. Dixson, Ndubuisi George Orji, Joseph Fu, Theodore V. Vorburger


The decreasing size of semiconductor features and the increasing structural complexity of advanced devices has placed continuously greater demands on manufacturing metrology-arising both from the measurement challenges of smaller feature sizes and the growing requirement to characterize structures in more than just a single critical dimension. For scanning electron microscopy (SEM), this has resulted in increasing sophistication of imaging models. For critical dimension atomic force microscopes (CD-AFM), this has resulted in the need for smaller and more complex tips. Carbon nanotube (CNT) tips have thus been the focus of much interest and effort by a number of researchers. However, there have been significant issues surrounding both manufacturing and using CNT tips. Specifically, the growth or attachment of CNTs to AFM cantilevers has been a challenge to fabrication of CNT tips, and the flexibility and resultant bending artifacts have presented challenges to using CNT tips. The Korea Research Institute for Standards and Science (KRISS) has invested considerable effort in the controlled fabrication of CNT tips and is collaborating with the National Institute of Standards and Technology (NIST) on the application of CNT tips for CD-AFM. Progress by KRISS in the precise control of CNT orientation, length, and end modification, using manipulation and focused ion beam processes, has allowed us to implement ball-capped CNT tips and bent CNT tips for CD-AFM. Using two different generations of CD-AFM instruments, we have evaluated these tip types by imaging a line/space grating and a programmed line edge roughness specimen. We concluded that these CNT are capable of scanning the profiles-including re-entrant sidewalls, but there remain important challenges to address-including tighter control of tip geometry and careful optimization of scan parameters and algorithms for using CNT tips.
Journal of Micro/Nanolithography, MEMS, and MOEMS


CD-AFM, atomic force microscope (AFM), carbon nanotube (CNT) tip, nano-manipulation, ion beam bending (IBB), ion beam induced deposition (IBID), critical dimension (CD) metrology


Choi, J. , Park, B. , Ahn, S. , Kim, D. , Lyou, J. , Dixson, R. , Orji, N. , Fu, J. and Vorburger, T. (2016), Evaluation of Carbon Nanotube Probes in Critical Dimension Atomic Force Microscopes, Journal of Micro/Nanolithography, MEMS, and MOEMS, [online],, (Accessed May 25, 2024)


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Created August 25, 2016, Updated October 12, 2021