Mapping buried nanostructures using subsurface ultrasonic resonance force microscopy

Es, M.H. van; Mohtashami, Abbas; Thijssen, Rutger; Piras, Daniele; Neer, P.L.M.J. van; Sadeghian, Hamed

doi:10.1016/j.ultramic.2017.09.005

Cited by 26 publications

(12 citation statements)

References 27 publications

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“…CR AFM has also been used to measure the viscoelastic loss tangents of polymer blends [3], study the effect of relative humidity on the viscoelastic properties of organic thin films [4], and conduct photorheological measurements to study curing kinetics of polymers [5]. Additionally, CR AFM has been used to measure buried, subsurface nanostructures [6,7,8,9] that are not visible in typical topographic AFM measurements. Finally, the principles of contact resonance have been used to enhance other popular modes of AFM, such as electrochemical strain microscopy (ESM) [10,11,12] and piezoresponse force microscopy [13,14] (PFM), and researchers have developed new experimental measurement procedures and techniques for CR AFM that aim to increase the accuracy of these coupled methods [15].…”

Section: Introductionmentioning

confidence: 99%

Contact Resonance Atomic Force Microscopy Using Long, Massive Tips

Jaquez-Moreno

Aureli

Tung

2019

Sensors

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In this work, we present a new theoretical model for use in contact resonance atomic force microscopy. This model incorporates the effects of a long, massive sensing tip and is especially useful to interpret operation in the so-called trolling mode. The model is based on traditional Euler–Bernoulli beam theory, whereby the effect of the tip as well as of the sample in contact, modeled as an elastic substrate, are captured by appropriate boundary conditions. A novel interpretation of the flexural and torsional modes of vibration of the cantilever, when not in contact with the sample, is used to estimate the inertia properties of the long, massive tip. Using this information, sample elastic properties are then estimated from the in-contact resonance frequencies of the system. The predictive capability of the proposed model is verified via finite element analysis. Different combinations of cantilever geometry, tip geometry, and sample stiffness are investigated. The model’s accurate predictive ranges are discussed and shown to outperform those of other popular models currently used in contact resonance atomic force microscopy.

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Section: Introductionmentioning

confidence: 99%

Contact Resonance Atomic Force Microscopy Using Long, Massive Tips

Jaquez-Moreno

Aureli

Tung

2019

Sensors

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“…Viscoelasticity based SSPM requires large indentation forces applied to the tip in order to extend the stress field in the sample and in that way probe the subsurface. Thus, the maximum detection depth of the method is limited to less than 1 μm 8,12 depending on the medium's compressive strength and the viscoelastic contrast between the subsurface feature and the surrounding medium. 2) Scattering 14 15 :…”

Section: Introductionmentioning

confidence: 99%

“…The scattered wave then travels towards the sample top surface, and the resulting sample top surface displacement is picked up by an AFM probe. The contact between tip and sample surface is described in literature by means of Hertz theory 8,12,17 . In Hertz theory the relation between the contact force and the resulting tip indentation is nonlinear.…”

Section: Introductionmentioning

confidence: 99%

“…The analytical expansion of such mixed frequencies shows that the process generates a low frequency component signal at the chosen modulation frequency (or twice the modulation frequency depending on the modulation scheme). Details of the experimental setup relevant for the downmixing are reported in the work by van Es et al 8 Typically the modulation frequency is chosen to be close to the contact resonance frequency of the cantilever (0.1 -1 MHz) to enhance the AFM sensitivity 18 .…”

Section: Introductionmentioning

confidence: 99%

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Optimization of acoustic coupling for bottom actuated scattering based subsurface scanning probe microscopy

Neer

Quesson

et al. 2019

Review of Scientific Instruments

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The characterization of buried nanoscale structures non-destructively is an important challenge in a number of applications, such as defect detection and metrology in the semiconductor industry. A promising technique is Subsurface Scanning Probe Microscopy (SSPM), which combines ultrasound with Atomic Force Microscopy (AFM). Initially, SSPM was used measure the viscoelastic contrast between a subsurface feature and its surrounding medium. However, by increasing the ultrasonic frequency to >1 GHz, it has been shown that SSPM can also measure acoustic impedance based contrasts. At these frequencies it becomes difficult to reliably couple the sound into the sample such that the AFM is able to pick up the scattered sound field. The cause is the existence of strong acoustic resonances in the sample, the transducer and the coupling layer-the liquid layer used to couple the sound energy from the transducer into the sample-in combination with the nonlinearity of the tipsample interaction. Thus, it is essential to control and measure the thickness of the coupling layer with nanometer accuracy. Here, we present the design of a mechanical clamp to ensure a stable acoustic coupling. Moreover, an acoustic method is presented to measure the coupling layer thickness in realtime. Stable coupling layers with thicknesses of 700 ± 2 nm were achieved over periods of 2-4 hours. Measurements of the downmixed AFM signals showed stable signal intensities for >1 hour. The clamp and monitoring method introduced here makes scattering based SSPM practical, robust and reliable and enables measurement periods of hours.

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“…In recent years we have investigated and optimized the performance of subsurface imaging of structures based on their (visco-)elastic properties using SPM. 1,8 Once the gaps between the structures have been filled with other materials, this technique, in principle, allows extracting all kinds of geometrical and material properties from the measured data. Thus it enables characterizing structures in 3 dimensions.…”

Section: Introductionmentioning

confidence: 99%

Quantitative tomography with subsurface scanning ultrasound resonance force microscopy

Fillinger

Sadeghian

2019

Metrology, Inspection, and Process Control for Microlithography XXXIII

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Extracting quantitative information about dimensions and material properties of buried structures is continuing to be an important but difficult task in metrology. Examples of questions asking for this capability include critical dimension metrology of fins such as the profile (bottom width, top width, height) or the presence and extent of voids. In recent years TNO has demonstrated the concept of using Atomic Force Microscopy (AFM) in combination with ultrasound to image buried structures based on their (visco-)elasticity in a technique called Subsurface Scanning Ultrasound Resonance Force Microscopy (SSURFM). We have successfully imaged structures less than 10 nm wide, as well as structures buried up to a micrometer deep. However, extracting quantitative information from this data is not trivial, as the induced stress field in the sample depends on many parameters in a non-linear way: experimental parameters such as applied force, tip size and tip shape, and geometry and material properties of the buried structures themselves. Therefore, measurements based on this technique have a point spread function which varies in a complicated way with the sample properties that need to be measured. However, a solid understanding of the physics and mechanics involved, and the modeling of the expected structures and their response to externally applied stress, enable quantitative measurements. We specifically show our progress on characterizing a sample comprising fins from a 7 nm node manufacturing test run.

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Mapping buried nanostructures using subsurface ultrasonic resonance force microscopy

Cited by 26 publications

References 27 publications

Contact Resonance Atomic Force Microscopy Using Long, Massive Tips

Contact Resonance Atomic Force Microscopy Using Long, Massive Tips

Optimization of acoustic coupling for bottom actuated scattering based subsurface scanning probe microscopy

Quantitative tomography with subsurface scanning ultrasound resonance force microscopy

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