From the motion sensor to the computer chip, in many products of daily life
components are used whose functioning is based on smallest structures of the
size of thousandths -- or even millionths -- of millimetres. These micro and
nano structures must be manufactured and assembled with the highest precision
so that in the end, the overall system will function smoothly.
 | | The micro probe used in the micro-nano CMM measures the form and the spacing of two reference spheres with diameters of two millimetres each. The figure shows a survey of the system and the proportions of measuring probe and measurement object in detail. (Credit: PTB) |
Because of this, details are important. Scientists at the Physikalisch-Technische
Bundesanstalt (PTB) have now developed a metrological scanning probe microscope
into a micro and nano coordinate measuring instrument. This allows dimensional
quantities with nanometer resolution also to be measured on three-dimensional
objects in an extraordinarily large measurement range of 25 mm x 25 mm x 5 mm.
The new device is already extensively being used at PTB - to a large part for
calibration orders from industry and research.
Often, such small dimensions can be grasped only when they are transferred
to everyday life. If we assume, for example, that someone lost a cube of sugar
within an area of 25 square kilometres - the new micro and nano coordinate
measuring instrument would not only be able to find it, but it would also be
able to determine its exact position and shape. This does not only apply to
plane surfaces, but also to three-dimensional landscapes, for example if the
cube of sugar were stuck to a steep wall.
As increasingly, components with structures in the micro- and nanometer range
are being used in industry, dimensional metrology on such structures is becoming
increasingly important. To meet the increasing requirements for 3D measurements
of micro and nano structures, 3D measuring probes newly developed at PTB were
incorporated in a metrological scanning probe microscope based on a commercial
nano-positioning system with integrated laser displacement sensors of the company
SIOS Messtechnik GmbH. The new functionalities given by the measuring probe
and the software extend the scanning probe microscope to a metrological micro/nano
coordinate measuring machine (CMM) which also allows 3D measurements conforming
to standards to be performed on micro and nano structures.
International intercomparisons on step-height standards and lattice structures
have shown that the measuring system is worldwide one of the most precise of
its kind. For step heights, measurement uncertainties in the subnanometer range
- and for measurements of the mean structure spacing on extensive lattice standards
even in the range of 10 picometers - have been achieved and confirmed in comparison
with optical diffraction measurements.
The new measuring instrument is available for dimensional precision measurements
with nm resolution on 3D micro and nano structures such as micro gears, micro
balls, hardness indenters and nano lattice standards as well as for comparisons
of measures; moreover, it serves as a platform for research and development
tasks. It is an important link between nano, micro and macro coordinate metrology.
Posted October 13th, 2009
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