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Non-contact distance measurement and profilometry using thermal near-field radiation towards a high resolution inspection and metrology solution

Author: Bijster, R.J.F. · Sadeghian Marnani, H. · Keulen, F. van
Publisher: SPIE
Source:Sanchez, M.I.Ukraintsev, V.A., 30th Conference on Metrology, Inspection, and Process Control for Microlithography, 22-25 February 2016, 9778
Proceedings of SPIE - The International Society for Optical Engineering
Identifier: 546177
ISBN: 9781510600133
Article number: 97780H
Keywords: Electronics · High resolution inspection · Thermal microscopy · Lenses · Profilometry · Uncertainty analysis · Units of measurement · Near field radiation · Optical near field · Optical performance · Sensitive calorimeter · Solid immersion lens · Process control · High Tech Systems & Materials · Industrial Innovation · Nano Technology · OM - Opto-Mechatronics · TS - Technical Sciences


Optical near-field technologies such as solid immersion lenses and hyperlenses are candidate solutions for high resolution and high throughput wafer inspection and metrology for the next technology nodes. Besides sub-diffraction limited optical performance, these concepts share the necessity of extreme proximity to the sample at distances that are measured in tens of nanometers. For the instrument this poses two major challenges: 1) how to measure the distance to the sample? and 2) how to position accurately and at high speed? For the first challenge near-field thermal radiation is proposed as a mechanism for an integrated distance sensor (patent pending). This sensor is realized by making a sensitive calorimeter (accuracy of 2:31nW root sum squared). When used for distance measurement an equivalent uncertainty of 1nm can be achieved for distances smaller than 100 nm. By scanning the distance sensor over the sample, thermal profilometry is realized, which can be used to inspect surfaces in a non-intrusive and non-contact way. This reduces wear of the probe and minimizes the likelihood of damaging the sample.