The Role of Tip-based Measurement in aHybrid Metrology Framework for Roll-to-Roll
Nanofabrication
Liam G. Connolly and Michael Cullinan*
Walker Department of Mechanical Engineering
The University of Texas at Austin
Austin, TX, USA 78712
E-mail: Michael.Cullinan@austin.utexas.edu

As the boundaries of minimum feature size, pitch, and aspect ratio are pushed back in
the rapid evolution of roll-to-roll (R2R) nanoimprint and nanoprinting manufacturing, a new
approach to nanoscale measurement for process control must also be developed to keep pace.
Where in traditional R2R manufacturing or micro-replication processes direct opticalinspection, and indirect methods such as scatterometry, ellipsometry, and diffractometry havebeen sufficient to provide defect detection and process control measurements in current art, asfabricated features shrink below the diffraction limit of visible light, new metrology techniquesmust be employed [1]–[12]. Further, while typical out-of-line methods such as critical dimension(CD)- and Tilt- scanning electron microscopy (SEM) and CD- atomic force microscopy (AFM)
are adequate for run-to-run process control in the traditional semiconductor fab environment,these slow, out-of-line tools do not sync up with the large-area, high-speed processing
environment of R2R nanomanufacturing [5], [13], [14].
To fill this metrology gap and provide direct, nanoscale topography data on fabricatedfeatures for in-line process control, a novel tip-based measurement device is employed – thesingle chip (sc)-AFM (ICSPI Corp.). The micro-electro-mechanical system (MEMS)
architecture leveraged by the sc-AFM packs all sensing and actuation necessary for nanometerscale topography measurements onto a compact ~1.1 mm2 footprint device at an incredible low
cost (~$250) as seen in Figure 1 [15]. This research seeks to leverage the extremely compact
packaging and resilient, micro-scale sensing and actuation mechanisms of sc-AFMs to achieve
in-line, nanoscale process control through a proof-of-concept metrology system which
positions an sc-AFM above a flexible web in a R2R system with less than ± 10 nm (1σ)
certainty in position in Z and machine directions as seen in Figure 2. This concept tool can
provide true nanometer scale topography measurements of flexible, hierarchical, andnanofeatured patterns in a 60 second step-and-scan process as shown by the scan of a butterfly
wing seen in Figure 3.
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Figure 1. sc-AFM MEMS device next to the N in United on a US Quarter

Figure 2. Nanometrology Proof-of-Concept Prototype System Overview [16]Figure 3. In-line sc-AFM Scan of Queen Butterfly Wing on Polycarbonate Substrate [16]