Proposal for new atomic force microscopy (AFM) imaging for a high aspect structure (digital probing mode AFM)

Hosaka, Sumio; Morimoto, Takafumi; Kuroda, Kazuaki; Kunitomo, Hiroyuki; Hiroki, Takenori; Kitsukawa, Tsuyoshi; Miwa, Shigeru; Yanagimoto, Hiroyuki; Murayama, Kazuro

doi:10.1016/s0167-9317(01)00551-2

Cited by 16 publications

(14 citation statements)

References 3 publications

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“…However, such probes encounter problems such as bending and slipping, which introduce serious errors. In order to achieve faithful measurement using the probe, we have developed a step-in mode technique [2,3]. The present research has demonstrated that the proposed method is suitable for CD-AFM and prevents bending of the probe by maintaining a constant gap between the probe and the sample surface during probe scanning in conventional AFM methods such as contact mode [1], non-contact mode [1,4,5] and tapping mode AFM [6].…”

Section: Introductionmentioning

confidence: 89%

“…The resonant base frequency is approximately 139.8 kHz, the conversion band width is approximately 1.3 kHz, and the FV conversion is approximately 26 mV/Hz. In step-in mode operation, (1) the probe is made to approach the sample surface and to control the force gradient constant after xy-scanning has completely stopped, (2) the probe is moved stepwise from pixel to pixel just after gap control is stopped, and it is lifted up from the sample surface, and (3) a step-in mode NC-AFM image is produced by repeating steps (1) and (2) while xy-scanning the probe over the surface [2,3]. This sequence is performed by modifying the software in the AFM system.…”

Section: Prototype Step-in Mode Nc-afmmentioning

confidence: 99%

“…† Corresponding author: hosaka@el.gunma-u.ac.jp ping on steep structures which caused the position error in the AFM measurement [2,8].…”

Section: Introductionmentioning

confidence: 99%

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Step-In Mode NC-AFM Using a Quadrature Frequency Demodulator for Observing High-Aspect Ratio Structures in Air

Hosaka

Terauchi

Takizawa

et al. 2011

e-J. Surf. Sci. Nanotechnol.

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We have investigated step-in mode non-contact atomic force microscopy (NC-AFM) for precise measurement of fine and steep structures having high aspect ratios. We have proposed piconewton controlled step-in mode AFM using NC-AFM to suppress bending and slipping of the probe on a slope. We have constructed a prototype of the step-in mode NC-AFM using a quadrature frequency demodulator for detecting the resonant frequency shift of the cantilever. Experiments revealed that the system was able to perform step-in mode NC-AFM even in air. We obtained a faithful AFM image of the steep structure of a dry-etched Si pattern without bending or slipping of the probe at approximately 2-3 pN using a sharp, slim probe, as compared with a step-in mode contact AFM image obtained at 1, 5, and 10 nN.

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Section: Introductionmentioning

confidence: 89%

Section: Prototype Step-in Mode Nc-afmmentioning

confidence: 99%

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Step-In Mode NC-AFM Using a Quadrature Frequency Demodulator for Observing High-Aspect Ratio Structures in Air

Hosaka

Terauchi

Takizawa

et al. 2011

e-J. Surf. Sci. Nanotechnol.

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“…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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“…We have a proprietary AFM scanning method named Step in mode® 7,8,9,10,11,12 . This method is illustrated in Figure 2.…”

Section: Introductionmentioning

confidence: 99%

An advanced AFM sensor for high-aspect ratio pattern profile in-line measurement

et al. 2006

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Design rule shrinkage and the wider adoption of new device structures such as STI, copper damascene interconnects, and deep trench structures have increased the necessity of in-line process monitoring of step heights and profiles of device structures. For monitoring active device patterns, not test patterns as in OCD, AFM is the only non-destructive 3D monitoring tool. The barriers to using AFM in-line monitoring are its slow throughput and the accuracy degradation associated with probe tip wear and spike noise caused by unwanted oscillation on the steep slopes of highaspect-ratio patterns. Our proprietary AFM scanning method, Step in mode®, is the method best suited to measuring high-aspect-ratio pattern profiles. Because the probe is not dragged on the sample surface as in conventional AFM, the profile trace fidelity across steep slopes is excellent. Because the probe does not oscillate and hit the sample at a high frequency as in AC scanning mode, this mode is free from unwanted spurious noises on steep sample slopes and incurs extremely little probe tip wear. To fully take advantage of the above properties, we have developed an AFM sensor optimized for in-line use, which produces accurate profile data at high speeds.The control scheme we have developed for the AFM sensor, which we call "Smart Step-in", elaborately analyses the contact force signal, enabling efficient probe tip scanning and a low and stable contact force. The mechanism of the AFM sensor has been optimized for the higher scanning rate and has improved the accuracy, such as the scanning planarity, position and height accuracy, and slope angle accuracy. Our prototype AFM sensor can scan high-aspectratio patterns while stabilizing the contact force at 3 nN. The step height measurement repeatability was 0.8 nm (3σ). A STI-like test pattern was scanned, and the steep sidewalls with angles of 84° were measured with high fidelity and without spurious noises.

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Proposal for new atomic force microscopy (AFM) imaging for a high aspect structure (digital probing mode AFM)

Cited by 16 publications

References 3 publications

Step-In Mode NC-AFM Using a Quadrature Frequency Demodulator for Observing High-Aspect Ratio Structures in Air

Step-In Mode NC-AFM Using a Quadrature Frequency Demodulator for Observing High-Aspect Ratio Structures in Air

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

An advanced AFM sensor for high-aspect ratio pattern profile in-line measurement

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