Brian Eves and Jeremias Seppä.
The public examination of the doctoral dissertation ”Linear and traceable scales for nanometrology” by Jeremias Seppä (senior research scientist at MIKES) took place at the Aalto University, School of Electrical Engineering on December 5, 2014. Dr. Brian Eves from the National Research Council Canada acted as the opponent.
Methods for the implementation of reliable, repeatable scales are central to all measurement techniques. Laser interferometers and diffractometers can be used for accurate dimensional measurements that are readily traceable to the definitions of the SI (Système International) units.
The thesis is a treatise on the correction of periodic error in laser interferometry and diffractometry and the application of these methods for accurate measurements. Capacitive sensors were used for measurement of periodic errors of a laser interferometer, and a rotary table and diffraction angles with error separation for determination of angle scale in a laser diffractometer. Applying the resulting corrections, leads to uncertainties in the picometre range for laser interferometry and diffraction grating calibration. For linearization of the measurement data, computational models in sets of linear equations were formulated and used, which results in Fourier-series type corrective terms for periodic errors.
The developed symmetric differential heterodyne laser interferometer with the periodic error correction using capacitive sensor was compared to an X-ray interferometer at National Physical Laboratory, UK. The results suggest that periodic nonlinearity error in the range of ten picometres or even lower is possible with the system.
The lateral and vertical scales of IT-MAFM (interferometrically traceable metrological atomic force microscope at MIKES) were produced with laser interferometry in the thesis. Grating standards calibrated with the laser diffractometer and characterized with the IT-MAFM were used to determine the measurement capabilities of tens of research laboratories with scanning electron microscopes (SEMs) and AFMs in the Nordic-Baltic region.
Stroboscopic scanning white light interferometer (SSWLI) is a device that can measure surfaces and interfaces in e.g. oscillating objects in different phases of the oscillation. In this work, an SSWLI at the University of Helsinki was also quasidynamically characterized with an uncertainty of 2.3 nm using a transfer standard with a vertically moving mirror and calibrated by using laser interferometry.
Additional information: Senior research scientist Jeremias Seppä,
firstname.lastname@example.org (Seppä->seppa), tel.
+358 2950 54465