title: Evaluation of carbon nanotube probes in critical dimension atomic force microscopes.
abstract: The decreasing size of semiconductor features and the increasing structural complexity of advanced devices have 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, this has resulted in increasing sophistication of imaging models. For critical dimension atomic force microscopes (CD-AFMs), 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 the manufacture and use of CNT tips. Specifically, the growth or attachment of CNTs to AFM cantilevers has been a challenge to the 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 on the application of CNT tips for CD-AFM. Progress by KRISS on 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 CNTs are capable of scanning the profiles of these structures, including re-entrant sidewalls, but there remain important challenges to address. These challenges include tighter control of tip geometry and careful optimization of scan parameters and algorithms for using CNT tips.
authors.affiliation: Korea Research Institute of Standards and Science, 267 Gajeong-Ro, Yuseong-Gu, Daejeon 305-345, Republic of Korea; Chungnam National University, 99 Daehak-Ro, Yuseong-Gu, Daejeon 34134, Republic of Korea.
authors.forename: Jinho
authors.initials: J
authors.lastname: Choi
authors.affiliation: Korea Research Institute of Standards and Science, 267 Gajeong-Ro, Yuseong-Gu, Daejeon 305-345, Republic of Korea.
authors.forename: Byong Chon
authors.initials: BC
authors.lastname: Park
authors.affiliation: Korea Research Institute of Standards and Science, 267 Gajeong-Ro, Yuseong-Gu, Daejeon 305-345, Republic of Korea.
authors.forename: Sang Jung
authors.initials: SJ
authors.lastname: Ahn
authors.affiliation: Korea Research Institute of Standards and Science, 267 Gajeong-Ro, Yuseong-Gu, Daejeon 305-345, Republic of Korea.
authors.forename: Dal-Hyun
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Chungnam National University, 99 Daehak-Ro, Yuseong-Gu, Daejeon 34134, Republic of Korea.
authors.forename: Joon
authors.initials: J
authors.lastname: Lyou
authors.affiliation: National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899-8212, United States.
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Dixson
authors.affiliation: National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899-8212, United States.
authors.forename: Ndubuisi G
authors.initials: NG
authors.lastname: Orji
authors.affiliation: National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899-8212, United States.
authors.forename: Joseph
authors.initials: J
authors.lastname: Fu
authors.affiliation: National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899-8212, United States.
authors.forename: Theodore V
authors.initials: TV
authors.lastname: Vorburger
keywords: atomic force microscope; carbon nanotube tip; critical dimension atomic force microscope; critical dimension metrology; ion beam bending; ion beam induced deposition; nanomanipulation