title: Tip characterization method using multi-feature characterizer for CD-AFM.
abstract: In atomic force microscopy (AFM) metrology, the tip is a key source of uncertainty. Images taken with an AFM show a change in feature width and shape that depends on tip geometry. This geometric dilation is more pronounced when measuring features with high aspect ratios, and makes it difficult to obtain absolute dimensions. In order to accurately measure nanoscale features using an AFM, the tip dimensions should be known with a high degree of precision. We evaluate a new AFM tip characterizer, and apply it to critical dimension AFM (CD-AFM) tips used for high aspect ratio features. The characterizer is made up of comb-shaped lines and spaces, and includes a series of gratings that could be used as an integrated nanoscale length reference. We also demonstrate a simulation method that could be used to specify what range of tip sizes and shapes the characterizer can measure. Our experiments show that for non re-entrant features, the results obtained with this characterizer are consistent to 1nm with the results obtained by using widely accepted but slower methods that are common practice in CD-AFM metrology. A validation of the integrated length standard using displacement interferometry indicates a uniformity of better than 0.75%, suggesting that the sample could be used as highly accurate and SI traceable lateral scale for the whole evaluation process.
authors.affiliation: Engineering Physics Division, National Institute of Standards and Technology, Gaithersburg, MD, United States. Electronic address: ndubuisi.orji@nist.gov.
authors.forename: Ndubuisi G
authors.initials: NG
authors.lastname: Orji
authors.affiliation: National Institute of Advanced Industrial Science and Technology AIST Tsukuba Central Research Institute of Instrumentation Frontier Nanoscale MicroSpectroscopic Analysis Group, Tsukuba, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Itoh
authors.affiliation: National Institute of Advanced Industrial Science and Technology AIST Tsukuba Central Research Institute of Instrumentation Frontier Nanoscale MicroSpectroscopic Analysis Group, Tsukuba, Japan.
authors.forename: Chumei
authors.initials: C
authors.lastname: Wang
authors.affiliation: Engineering Physics Division, National Institute of Standards and Technology, Gaithersburg, MD, United States.
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Dixson
authors.affiliation: Engineering Physics Division, National Institute of Standards and Technology, Gaithersburg, MD, United States; Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431, United States.
authors.forename: Peter S
authors.initials: PS
authors.lastname: Walecki
authors.affiliation: nanotools GmbH, Reichenbachstr. 33, 80469 Munich, Germany.
authors.forename: Sebastian W
authors.initials: SW
authors.lastname: Schmidt
authors.affiliation: nanotools GmbH, Reichenbachstr. 33, 80469 Munich, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Irmer
keywords: Critical dimension atomic force microscope; Tip characterizer; Tip dilation