Three-dimensional metrology with side-wall measurement using tilt-scanning operation in digital probing AFM

Murayama, Kazuro; Gonda, Satoshi; Koyanagi, Hajime; Terasawa, Tsuneo

doi:10.1117/12.654346

Cited by 10 publications

(13 citation statements)

References 7 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: 85%

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: 85%

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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“…In a previous report 26 , we have discussed the modeling of CNT probe deflection, which plays an important role in correcting the AFM image. Hence, we just summarize it in this report.…”

Section: Modeling Of Torsional Signal From the Cantilever Caused By Pmentioning

confidence: 99%

“…We have discussed in-depth how to estimate the deflection amount caused by the van der Waals attractive force in a previous report 26 . Hence, we just show the resulting graph in this report.…”

Section: Modeling Of Probe Deflection Caused By Attractive Force Frommentioning

confidence: 99%

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AFM method for sidewall measurement through CNT probe deformation correction and its accuracy evaluation

Watanabe

Baba

Nakata

et al. 2009

Metrology, Inspection, and Process Control for Microlithography XXIII

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To use atomic force microscope (AFM) to measure dense patterns of 32-nm node structures, there is a difficulty in providing flared probes that go into narrow vertical features. Using carbon nanotube (CNT) probes is a possible alternative. However, even with its extremely high stiffness, van der Waals attractive force from steep sidewalls bends CNT probes. This probe deflection effect causes deformation (or "swelling") of the measured profile. When measuring 100-nm-high vertical sidewalls with a 24-nm-diameter and 220-nm-long CNT probe, the probe deflection can cause a bottom CD bias of 13.5 nm. This phenomenon is inevitable when using long, thin probes whichever scanning method is used. We proposed a method to deconvolve this probe deflection effect. By detecting torsional motion of the base cantilever for the CNT probe, it is possible to estimate the amount of CNT probe deflection. Using this information, we have developed a technique for deconvolving the probe deformation effect from measured profiles. This technique, in combination with deconvolution of the probe shape effect, enables vertical sidewall profile measurement.We have quantitatively evaluated the performance of the proposed method using an improved version of a "tip characterizers" developed at the National Institute of Advanced Industrial Science and Technology (AIST), which has a well-defined high-aspect-ratio line and space structure with a variety of widths ranging from 10 to 60 nm. The critical dimension (CD) values of the line features measured with the proposed AFM method showed good matches to TEMcalibrated CD values. The biases were within a range of ±1.7 nm for combinations of three different probes, five different patterns, and two different threshold heights, which is a remarkable improvement from the bias range of ±4.7 nm with the conventional probe tip shape deconvolution method. The static repeatability was 0.54 nm (3σ), compared to 1.1 nm with the conventional method. Using a 330-nm-deep tip characterizer, we also proved that a 36-nm-narrow groove could be clearly imaged.

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“…StepIn mode combined with CNT probes has been used successfully 22 . To monitor sidewall shapes, Tilt StepIn mode, in which the CNT probe is tilted and obliquely approached to sampling points along sidewalls, has also been developed 24 .…”

Section: Introductionmentioning

confidence: 99%

A novel AFM method for sidewall measurement of high-aspect ratio patterns

et al. 2008

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To use atomic force microscope (AFM) to measure dense patterns of 32-nm node structures, there is a difficulty in providing flared probes that go into narrow vertical features. Using carbon nanotube (CNT) probes is a possible alternative. However, even with its extremely high stiffness, van der Waals attractive force from steep sidewalls bends CNT probes. This probe deflection effect causes deformation (or "swelling") of the measured profile. When measuring 100-nm-high vertical sidewalls with a 24-nm-diameter and 220-nm-long CNT probe, the probe deflection can cause a bottom CD bias of 13.5 nm. This phenomenon is inevitable when using long, thin probes whichever scanning method is used.We have developed a method of deconvolving this probe deflection effect that is well suited to our AFM scanning mode, AdvancedStep-in TM mode. In this scanning mode, the probe is not dragged on the sample surface but approaches the sample surface vertically at each measurement point. The CNT probe deformation is stable because we do not use cantilever oscillation that can cause instability, but we detect static flexure of the cantilever. Consequently, it is possible to estimate the amount of CNT probe deflection by detecting the degree of cantilever torsion. Using this information, we have developed a technique for deconvolving the probe deformation effect from measured profiles. This technique in combination with deconvolution of the probe shape effect makes vertical sidewall profile measurement possible.

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Three-dimensional metrology with side-wall measurement using tilt-scanning operation in digital probing AFM

Cited by 10 publications

References 7 publications

Evaluation of carbon nanotube probes in critical dimension atomic force microscopes

Evaluation of carbon nanotube probes in critical dimension atomic force microscopes

AFM method for sidewall measurement through CNT probe deformation correction and its accuracy evaluation

A novel AFM method for sidewall measurement of high-aspect ratio patterns

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