Calibrated scanning force microscope with capabilities in the subnanometre range (original) (raw)
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Error Sources in Atomic Force Microscopy for Dimensional Measurements: Taxonomy and Modeling
Journal of Manufacturing Science and Engineering, 2010
This paper aimed at identifying the error sources that occur in dimensional measurements performed using atomic force microscopy. In particular, a set of characterization techniques for errors quantification is presented. The discussion on error sources is organized in four main categories: scanning system, tip-surface interaction, environment, and data processing. The discussed errors include scaling effects, squareness errors, hysteresis, creep, tip convolution, and thermal drift. A mathematical model of the measurement system is eventually described, as a reference basis for errors characterization, with an applicative example on a reference silicon grating.
Journal of Micro/Nanolithography, MEMS, and MOEMS, 2011
The National Institute of Standards and Technology (NIST), Advanced Surface Microscopy (ASM), and the National Metrology Centre (NMC) of the Agency for Science, Technology, and Research (A*STAR) in Singapore have completed a three-way interlaboratory comparison of traceable pitch measurements using atomic force microscopy (AFM). The specimen being used for this comparison is provided by ASM and consists of SiO 2 lines having a 70-nm pitch patterned on a silicon substrate. For this comparison, NIST used its calibrated atomic force microscope (C-AFM), an AFM with incorporated displacement interferometry, to participate in this comparison. ASM used a commercially available AFM with an open-loop scanner, calibrated with a 144-nm pitch transfer standard. NMC/A*STAR used a large scanning range metrological atomic force microscope with He-Ne laser displacement interferometry incorporated. The three participants have independently established traceability to the SI (International System of Units) meter. The results obtained by the three organizations are in agreement within their expanded uncertainties and at the level of a few parts in 10 4. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).
International Conferences on Multi-Material Micro Manufacture, 4M/International Conferences on Micro Manufacturing, ICOMM, 2009
Atomic Force Microscopy (AFM) is a powerful technique providing 3D surface topographies with very high resolution in both lateral and vertical direction. Thanks to its relatively easy use, AFM can be well introduced in process control, gaining great advantage in research as well as in the evaluation of final product characteristics. The paper considers quantitative application of AFM measurements for industrial applications. In particular the influence and subsequent optimization of scanning parameters on the precision of AFM maps is discussed, with particular attention to scan speed and interaction force when measuring a one-dimensional grating with triangular profile. The aim is then maximization of information from collected data and minimization of measurement variability and scan time. Optimized scan setting is then applied to measure surface defects of micro injection moulded components. Results show the detrimental effect of high speed on the measurement of deep valleys as well as the effect of force on vertical measurements accuracy. Horizontal measurements were also performed, highlighting the prevailing effect of scan speed.
Microsystem Technologies, 2009
A two-dimensional nano-scale measuring system utilizing a two-dimensional combined optical and X-ray interferometer (2D COXI) was developed for the standardization of measurement in the nanometer region. The system consists of a 2D COXI and an atomic force microscope (AFM). The designed, two-dimensional, flexure-stage scans and the cantilever tip probes the nanostructure of the specimen. The calibrated optical interferometers in the 2D COXI were used to measure two-dimensional nano-scale lengths. The accuracy of the optical interferometers was enhanced to enable sub-nanometer measurements. To demonstrate the nano-scale measuring system, we used it to measure the nano-scale pitches of gratings.
Ultramicroscopy, 2015
A novel atomic force microscope (AFM) dual-probe caliper for critical dimension (CD) metrology has been developed. The caliper is equipped with two facing tilted optical fiber probes (OFPs) wherein each can be used independently to scan either sidewall of micro and nanostructures. The OFP tip with length up to 500μm (aspect ratio 10:1, apex diameter ⩾10nm) has unique features of scanning deep trenches and imaging sidewalls of relatively high steps with exclusive profiling possibilities. The caliper arms-OFPs can be accurately aligned with a well calibrated opening distance. The line width, line edge roughness, line width roughness, groove width and CD angles can be measured through serial scan of adjacent or opposite sidewalls with each probe. Capabilities of the presented AFM caliper have been validated through experimental CD measurement results of comb microstructures and AFM calibration grating TGZ3.
Tehnički glasnik, 2024
The atomic force microscope (AFM) enables the measurement of sample surfaces at the nanoscale. Reference standards with calibration gratings are used for the adjustment and verification of AFM measurement devices. Thus far, there are no guidelines or guides available in the field of atomic force microscopy that analyze the influence of input parameters on the quality of measurement results, nor has the measurement uncertainty of the results been estimated. Given the complex functional relationship between input and output variables, which cannot always be explicitly expressed, one of the primary challenges is how to evaluate the measurement uncertainty of the results. The measurement uncertainty of the calibration grating step height on the AFM reference standard was evaluated using the Monte Carlo simulation method. The measurements within this study were conducted using a commercial, industrial atomic force microscope.
2014
Reliability of measurement is a crucial element of both research and industry. Metrological traceability to the SI unit metre guarantees commensurate units, also at nanometre range. In this thesis, a traceability chain is established for nanometre scale measurements. Measurement instruments and methods were developed for accurate measurements, calibration of instruments and transfer standards, and uncertainty estimations. A metrological atomic force microscope (MAFM) was developed and characterized. The MAFM can be used in the calibration of transfer standards and in accurate AFM measurements. Calibration methods for commercial AFMs were developed. A laser diffractometer was also developed for accurate calibration of 1-D and 2-D gratings with a standard uncertainty of several tens of picometres. Laser interferometric position measurement with a calibrated vacuum wavelength is directly traceable to the realization of the metre if measuring full interferometer fringes, but there is small nonlinearity in sub-fringe measurements. Therefore, in sub-nanometre measurements the nonlinearity of the interferometer needs to be corrected. A method for this correction was developed. Laser diffraction measurement is a very accurate method for characterization of grating pitch. One of the main uncertainty sources is the uncertainty of the measured diffraction angle. Therefore, a method for calibration of the rotary table of the laser diffraction setup was developed. The method can be used also in the realization of angle scale. Methods for transfer standard calibration were developed for both pitch and step height calibration by MAFM. An acoustic method was developed for compensation of the refractive index of air in interferometric measurements. Sub-nanometre uncertainty can be reached with this method. Characterization of instruments, validation of methods and uncertainty estimations are a crucial part of traceability. Therefore, uncertainty estimates based on the characterization of the instruments are given for all measurements in this thesis. Comparisons between laboratories are the best way to ensure commensurate measurements. International comparison results between national metrology institutes for pitch and step height transfer standards are listed. I would like to thank all my colleagues at MIKES, especially MSc Jeremias Seppä, Mr Asko Rantanen, PhD Hannu Husu and MSc Aarni Iho, and the whole length group. It has been a pleasure working with you. Many thanks to PhD Mikko Merimaa for the discussions and comments on the thesis. Thanks also to PhD Kaj Nyholm for his valuable comments. I am grateful to Mr Leonid Mihaljov and AcWaCo Ltd for their kind cooperation. I would like to thank all my international colleagues for their cooperation and valuable input throughout the years. I am also thankful to the University of Helsinki, Department of Physics, and Professor Juhani Keinonen for the inspiring atmosphere during my studies and initial years in the academic world, and to Professor Jyrki Räisänen for his support at the very end of the work. Many thanks to the preliminary examiners Professor Janne Ruokolainen and Professor Markus Ahlskog for their effort. Thanks to Adelaide Lönnberg for revising the English language of the thesis. I would like to acknowledge the Academy of Finland for the financial support, and NGS-NANO for their support. Finally, I would thank my family, Ilkka and Lassi, for their encouragement and support.
Design and characterization of MIKES metrological atomic force microscope
Precision Engineering, 2010
An interferometrically traceable metrological atomic force microscope (IT-MAFM) has been developed at MIKES. It can be used for traceable atomic force microscope (AFM) measurements and for calibration of transfer standards of scanning probe microscopes (SPMs). Sample position is measured online by 3 axes of laser interferometers. A novel and simple method for detection and online correction of the interferometer nonlinearity was developed. Effect of the nonlinearity in measurements is demonstrated. In the design, special attention has been paid to elimination of external disturbances like electric noise, acoustic noise, ambient temperature variations and vibrations. The instrument has been carefully characterized. The largest uncertainty components are caused by Abbe errors, orthogonality errors, drifts and noise. Noise level in Z direction was 0.25 nm, and in X and Y directions 0.36 nm and 0.31 nm, respectively. Standard uncertainties for X, Y and Z coordinates are u cx = q[0.48; 0.04x; 0.17y; 1.7z; 2 time] nm, u cy = q[0.45; 0.31x; 0.07y; 0.14z; 4 time] nm and u cz = q[0.42; 3x; 7.2y; 0.18z; 2 time] nm where x, y, z are in m and time in h. Standard uncertainty for 300 nm pitch is 0.023 nm,and for 7 nm step height measurement is 0.35 nm. Uncertainty estimates are supported by an international comparison.
Review of Scientific Instruments, 2008
We present here a method to calibrate the lateral force in the atomic force microscope. This method makes use of an accurately calibrated force sensor composed of a tipless piezoresistive cantilever and corresponding signal amplifying and processing electronics. Two ways of force loading with different loading points were compared by scanning the top and side edges of the piezoresistive cantilever. Conversion factors between the lateral force and photodiode signal using three types of atomic force microscope cantilevers with rectangular geometries ͑normal spring constants from 0.092 to 1.24 N / m and lateral stiffness from 10.34 to 101.06 N / m͒ were measured in experiments using the proposed method. When used properly, this method calibrates the conversion factors that are accurate to Ϯ12.4% or better. This standard has less error than the commonly used method based on the cantilever's beam mechanics. Methods such of this allow accurate and direct conversion between lateral forces and photodiode signals without any knowledge of the cantilevers and the laser measuring system.