Carbon nanotube AFM probes for microlithography process control

Liu, Bernard Haochih; Fong, David; Dahlen, Gregory A.; Osborn, Marc; Hand, Seán; Osborne, James F.

doi:10.1117/12.656807

Cited by 13 publications

(4 citation statements)

References 9 publications

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“…However, there has been progress in the application of CNT tips to CD-AFM by a number of researchers. 22,24 The considerably greater wear resistance of CNT tips has also been demonstrated in this context.…”

Section: Introductionmentioning

confidence: 82%

Evaluation of carbon nanotube probes in critical dimension atomic force microscopes

Choi

Park

Ahn

et al. 2016

J. Micro/Nanolith. MEMS MOEMS

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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.

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Section: Introductionmentioning

confidence: 82%

Evaluation of carbon nanotube probes in critical dimension atomic force microscopes

Choi

Park

Ahn

et al. 2016

J. Micro/Nanolith. MEMS MOEMS

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“…Carbon nanotubes (CNTs) [1,2] have many actual and potential applications in different fields of engineering (e.g. sensors [3], actuators [4,5], springs [6], resonators [7,8], reinforcement elements [9][10][11][12], probes [13][14][15][16]) thanks to their outstanding mechanical, optical, thermal and electrical properties [17][18][19][20]. Even though discrete modeling techniques can precisely mimic the response of the corresponding media with a proper choice of interatomic potential and realistic boundary/loading conditions [21][22][23][24][25][26] [ [27][28][29][30], limitations are imposed both on time and scale of the problem due to computational concerns [31], while experimental methods might suffer from physical challenges (e.g.…”

Section: Applications and Literature Reviewmentioning

confidence: 99%

Bending characteristics of carbon nanotubes: Micropolar elasticity models and molecular dynamics simulations

Izadi

Tuna

Trovalusci

et al. 2021

Mechanics of Advanced Materials and Structures

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The present paper aims at evaluating non-classical continuum parameters for each class of armchair and zigzag single-walled CNTs focusing on the scale effect in their flexural behavior observed in molecular dynamics (MD) simulations. Through a non-linear optimization approach, the bending rigidities obtained from atomistic simulations are compared to those derived from non-classical continua. For MD simulations, a novel method ensuring pure bending is introduced and for continuum modeling, micropolar, constrained micropolar, and modified couple stress theories are employed. The results reveal that adopted non-classical theories, notably micropolar theory, provide reasonable outcomes with an obvious failure of classical Cauchy theory.

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“…Several examples of IVPS/SOCS tip qualification were given in [2][3][4]. As CD AFM continues to find new applications in semiconductor production with new probe designs, the IVPS/SOCS approach can no longer satisfy several aspects of the metrology operation.…”

Section: Introductionmentioning

confidence: 99%

Advanced CD-AFM probe tip shape characterization for metrology accuracy and throughput

et al. 2007

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As semiconductor and data storage industries apply Critical Dimension Atomic Force Microscopy (CD-AFM) for their metrology needs in research and production, (1) measurement accuracy/repeatability and (2) measurement throughput are the major criteria for acceptance. However, these two requirements are usually contradictory for a metrology instrument. For example, a scatterometer can take a snapshot of a wafer in seconds, but such indirect CD measurements are biased by the availability of library models and uncertainty of computer simulations. Transmission Electron Microscopy (TEM) provides an atomic-scale resolution that is traceable back to the lattice structure of atoms, yet the cross-section data is highly localized and can take days or weeks to acquire.In the case of CD-AFM, since the scanning probe physically interacts with the structure of interest at a close proximity, the determination of sample morphology comes from direct measurements. Therefore, the measurement uncertainty can be attributed to: (1) AFM probe tip shapes and (2) system control and scan algorithms. For the former, past efforts have been mainly focused on improving metrology accuracy and repeatability by reducing the dimensional uncertainty of a tip shape. This approach includes characterizing the probe tip shape periodically. Inevitably, such tip shape calibration procedure takes time (approximately 5 min) and burdens production throughput.In this paper, we introduce several new methods for AFM probe tip shape characterization with different designs of tip shape characterizers. The new tip shape characterizers were designed to address the limitation of current structures. First, a single silicon overhang structure with wear-resistant coatings was used as the characterizer for both tip width and tip shape profile. Tip-to-tip scan repeatability data (0.7 nm 3 Sigma) and measurement statistics suggest an improvement over present state-of-the-art practice. Tip shape profiles of several high aspect ratio (20:1 to 25:1), low lateral stiffness probes were successfully characterized with this method. Furthermore, the use of single characterizer provides an opportunity to shorten tool calibration time, and consequently, increase measurement throughput.In addition, a carbon nanotube characterizer prototype is proposed for CD-AFM. When scanning probe geometry shrinks with semiconductor technology nodes, it has become a challenge to characterize a probe with a few tens of nanometer of width with a micrometer-size characterizer. Using a comparable or smaller size of characterizer for a small (20 to 50 nm) AFM probe not only reduces the dimensional uncertainty, but also expands the 2-D profiling capability of current tip shape characterization.We will discuss limitations of current tip shape profiling techniques, proof-of-concept experiments for new characterizers, implementation of new tip shape characterization methods, and approaches to increasing measurement throughput. BACKGROUNDCD AFM is a direct metrology instrument that uses a probe tip to acqui...

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Carbon nanotube AFM probes for microlithography process control

Cited by 13 publications

References 9 publications

Evaluation of carbon nanotube probes in critical dimension atomic force microscopes

Evaluation of carbon nanotube probes in critical dimension atomic force microscopes

Bending characteristics of carbon nanotubes: Micropolar elasticity models and molecular dynamics simulations

Advanced CD-AFM probe tip shape characterization for metrology accuracy and throughput

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