New AFM imaging for observing a high aspect structure

Hosaka, Sumio; Morimoto, Takafumi; Kuroda, Hiroshi; Minomoto, Yasushi; Kembo, Yukio; Koyabu, Hirokazu

doi:10.1016/s0169-4332(01)00934-5

Cited by 16 publications

(10 citation statements)

References 7 publications

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“…Here, we explain the StepIn™ mode 15,16,17,18,19 . In this method, which is illustrated in Figure 3, after each height sampling point (i.e., measurement pixel), the AFM probe is retracted to a height where the probe tip does not detect short distance forces (such as van der Waals forces and capillary forces) from the sample, and the probe is moved laterally to the next measuring point (1).…”

Section: Introductionmentioning

confidence: 99%

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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Section: Introductionmentioning

confidence: 99%

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

Self Cite

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show abstract

“…Here, we explain StepIn™ mode 13,14,15,16,17 . In this method, which is illustrated in Figure 2, after each height sampling point (i.e., measurement pixel), the AFM probe is retracted to a height where the probe tip does not detect short distance forces (such as van der Waals forces and capillary forces) from the sample, and the probe is moved laterally to the next measuring point (1).…”

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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“…For these applications, special tips with high aspect ratios are required, including exotic tips such as carbon nanotubes (Bhushan et al , 2004). Alternatively, a ‘hopping’ approach to the X‐Y scanning of the AFM has been shown to help reduce tip‐sample convolution (Hosaka et al , 2002). The Phoenix AFM (Akiyama et al , 2001; Pike et al , 2001) however, being a space‐qualified instrument, is limited in its range of available tip geometries, as robustness is a key criteria for space‐bound hardware, and high‐aspect ratio tips tend to be very fragile and more difficult to use.…”

Section: Introductionmentioning

confidence: 99%

AFM investigation of Martian soil simulants on micromachined Si substrates

Vijendran

Sykulska

Pike

2007

Journal of Microscopy

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SummaryThe micro and nanostructures of Martian soil simulants with particles in the micrometre-size range have been studied using a combination of optical and atomic force microscopy (AFM) in preparation for the 2007 NASA Phoenix Mars Lander mission. The operation of an atomic force microscope on samples of micrometre-sized soil particles is a poorly investigated area where the unwanted interaction between the scanning tip and loose particles results in poor image quality and tip contamination by the sample. In order to mitigate these effects, etched silicon substrates with a variety of features have been used to facilitate the sorting and gripping of particles. From these experiments, a number of patterns were identified that were particularly good at isolating and immobilizing particles for AFM imaging. This data was used to guide the design of micromachined substrates for the Phoenix AFM. Both individual particles as well as aggregates were successfully imaged, and information on sizes, shapes and surface morphologies were obtained. This study highlights both the strengths and weaknesses of AFM for the potential in situ investigation of Martian soil and dust. Also presented are more general findings of the limiting operational constraints that exist when attempting the AFM of high aspect ratio particles with current technology. The performance of the final designs of the substrates incorporated on Phoenix will be described in a later paper.

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New AFM imaging for observing a high aspect structure

Cited by 16 publications

References 7 publications

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

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

AFM investigation of Martian soil simulants on micromachined Si substrates

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