A method is described for the calibration of vertical piezoelectric transducer (PZT) stages using a large range metrological atomic force microscope (LRM-AFM). A vertical PZT stage is mounted onto the system and an optical-flat sample is attached on the top of the PZT stage. The AFM probe is operated in contact mode and used as a null indicator to measure the movement of the optical-flat as it is driven by the PZT stage. As the PZT stage is scanned vertically, the AFM probe is in contact with the test surface without lateral scanning. The displacement of the vertical stage of the LRM-AFM is measured by the integrated laser interferometer, and the corresponding laser interferometer readings and the nominal position of the PZT stage are recorded. This body of data is then used to establish the relationship between the laser interferometer reading and the nominal displacement of the PZT stage. Our results show that this method can be used to calibrate PZT stages up to a range of 250 µm with an expanded uncertainty of less than 5 nm.
In this paper, a method for the calibration of vertical PZT stages using a large range metrological atomic force
microscope (LRM-AFM) is described. A vertical PZT stage is mounted onto the system and an optical-flat sample is
attached on the top of the PZT stage. The AFM probe working in the contact mode is used as a null indicator which is
sensitive to the movement of the optical-flat sample directly driven by the vertical PZT stage. At each state of the PZT
stage movement, the AFM probe approaches to the test surface without horizontal scanning in the system. The
displacement of the vertical stage is measured by the laser interferometer in LRM-AFM and the corresponding laser
interferometer readings and the movements of the PZT stage are recorded. All collected data are retrieved to establish the
relationship of the laser interferometer reading versus the PZT stage displacement. The results show that the system is
capable of calibrating PZT stage in the range of up to 250 μm with an expanded uncertainty of less than 5 nm.
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 SiO2 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 104.
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 SiO2 lines having a 70 nm
pitch patterned on a silicon substrate.
NIST has a multifaceted program in atomic force microscope (AFM) dimensional metrology. One component of this
effort is a custom in-house metrology AFM, called the calibrated AFM (C-AFM). The NIST C-AFM has displacement
metrology for all three axes traceable to the 633 nm wavelength of the iodine-stabilized He-Ne laser - a recommended
wavelength for realization of the SI (Système International d'Unités, or International System of Units) meter. NIST
used the C-AFM to participate in this comparison.
ASM used a commercially available AFM with an open-loop scanner, calibrated by a 144 nm pitch transfer standard. In
a prior collaboration with Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute,
ASM's transfer standard was calibrated using PTB's traceable optical diffractometry instrument. Thus, ASM's
measurements are also traceable to the SI meter.
NMC/A*STAR used a large scanning range metrological atomic force microscope (LRM-AFM). The LRM-AFM
integrates an AFM scanning head into a nano-stage equipped with three built-in He-Ne laser interferometers so that its
measurement related to the motion on all three axes is directly traceable to the SI meter.
The measurements for this interlaboratory comparison have been completed and the results are in agreement within
their expanded uncertainties and at the level of a few parts in 104.
KEYWORDS: Optical spheres, 3D metrology, Uncertainty analysis, Silicon, Laser interferometry, Standards development, Signal detection, Manufacturing, Sensors, Control systems
Micro-coordinate measuring machines (micro-CMMs) with small probes (φ300 μm or smaller), low probing force and
high accuracy working stage have been developed in recent years for three-dimensional (3D) measurement of micro
structures. In general, the performance of the micro-CMM depends on the accuracy of its working stage and the probing
system. The accuracy of the working stage of a micro CMM can be assessed by laser interferometry to the order of a few
tens of nanometers. However, the accuracy of its probing system is difficult to assess due to the small probe size and low
probing force. The probing error of a micro-CMM (model F25 by Carl Zeiss) was investigated at our laboratory. The
probes used in the system are based on silicon membrane and piezo-resistive elements. The stylus size of the probes
ranges from φ120 μm to φ300 μm. The effect of various sources, including the stylus size, on the probing error of the
system was evaluated by means of certified precision spheres with reference to ISO 10360-2:2001. Based on the results
obtained, possible ways to reduce the probing error are discussed. This is illustrated by the uncertainty analysis of the
diameter measurements of a ring gauge using the system.
The rapid advancement of nanotechnology is increasingly demanding measurements carried out at nano-scale be more
accurate, comparable and traceable to the international standards of units (the SI). The Atomic Force Microscope (AFM)
is a very powerful tool for the measurement of surface texture and micro-/nano-structures, with wide applications in
nanotechnology. However, the traceability and accuracy of quantitative measurements made by commercial AFMs are
often questionable and large discrepancies among them have been reported. This paper describes a metrological AFM
developed at the National Metrology Centre (NMC) which has a very large scanning range with nanometre uncertainty.
In order to achieve direct traceability to the SI, the system was constructed by integrating an AFM probe with a 3-axis
nano-translation stage furnished with high performance autocollimators and laser interferometers along its X, Y and Z
axes on a metrological frame. The large scanning range (25 mm × 25 mm × 5 mm) enables the system to be used for
surface inspection on much larger samples than those allowed in normal commercial AFMs. Details of the system design
and operation will be described in the paper. The uncertainty evaluation was done using certified step height, 1D/2D
lateral pitch gratings. The experimental results show that the system is capable of achieving an uncertainty in the order
of a few nanometres, which demonstrates that the system is suitable for providing traceability to commercial scanning
probe microscopes (SPMs) including AFMs through calibrated transfer artefacts.
Gauge blocks, line scales and polygons are precision dimensional standards widely used for the dissemination of linear and angular quantities. Comparisons on these standards have been carried out among Singapore Productivity and Standards Board in Singapore, Commonwealth Scientific and Industrial Research Organization in Australia and National Metrology Institute of Japan/National Institute of Advanced Industrial Science and Technology in Japan. The standards include a set of five ceramic gauge blocks with sizes of 1 mm, 3 mm, 6 mm, 25 mm and 100 mm, a 100 mm and 200 mm glass scales, and an eight-sided 45 degrees glass polygon. The results of comparisons are described in this paper.
A special calibration tool has been developed for a CCD camera based vision system in an automatic assembly machine. The machine is used to attach orifice plates onto a silicon wafer in a production process. The center locations of the positioning circular holes on the plate must be controlled accurately to coincide with those on the wafer die before they are attached together by UV curing. Although CCD camera based vision systems are widely used for accurate positioning and dimensional measurements in precision engineering, electronics and semiconductor industry, their calibrations are normally done by artefacts with plane patterns. These artefacts are therefore restricted to only two dimensional measurements. The calibration tool we developed was to check the positioning accuracy of circular objects in a two-layered structure. It can also be used to determine parallax errors, non-linearity and spatial non- uniformity errors as well as repeatability of the vision system with an uncertainty at sub-micrometer level. The design, calibration and performance of the tool are described in detail in this paper.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.