DOI: 10.1007/s00339-003-2273-7 Appl. Phys. A 78, 645–649 (2004) Materials Science & Processing Applied Physics A p. thomsen-schmidt 1, ✉ k. hasche 1 g. ulm 1 k. herrmann 1 m. krumrey 1 g. ade 1 j. st ¨ umpel 1 i. busch 1 s. sch ¨ adlich 2 a. schindler 3 w. frank 3 d. hirsch 3 m. procop 4 u. beck 4 Realisation and metrological characterisation of thickness standards below 100 nm 1 Physikalisch-Technische Bundesanstalt, Braunschweig und Berlin (PTB), Bundesallee 100, 38116 Braunschweig, Germany 2 Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS), Dresden, Germany 3 Institut für Oberflächenmodifizierung (IOM), Leipzig, Germany 4 Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin, Germany Received: 15 November 2002/Accepted: 18 June 2003 Published online: 12 November 2003 • © Springer-Verlag 2003 ABSTRACT High-accuracy film thickness measurements in the range below 100 nm can be made by various complex methods like spectral ellipsometry (SE), scanning force microscopy (SFM), grazing incidence X-ray reflectometry (GIXR), or X-ray fluorescence analysis (XRF). The measurement results achieved with these methods are based on different interactions between the film and the probe. A key question in nanotechnology is how to achieve consistent results on a level of uncertainty below one nanometre with different techniques. Two different types of thickness standards are realised. Metal film standards for X-ray techniques in the thickness range 10 to 50 nm are calibrated by GIXR with monochromatised synchrotron radiation of 8048 eV. The results obtained at four different facilities show excellent agreement. SiO 2 on Si stan- dards for SE and SFM in the thickness range 6 to 1000 nm are calibrated by GIXR with monochromatised synchrotron radia- tion of 1841 eV and with a metrological SFM. Consistent results within the combined uncertainties are obtained with the two methods. Surfaces and interfaces of both types of standards are additionally investigated by transmission electron microscopy (TEM). PACS 61.10.Kw; 68.55.Jk; 06.20.Fn; 06.60.Mr; 07.79.Lh 1 Introduction Nanotechnology is a field with one of the greatest potentials for growth in the modern economy. Therefore, re- liable measurement tools with high resolution and accuracy need to be developed and tested. The manufacture and meas- urement of homogeneous thin films in the thickness range below 100 nm with uncertainty values around 0.2 nm are im- portant techniques for the semiconductor industry, optical equipment, and X-ray technology. Calibrated reference standards provided and investigated by national metrological institutes are a fundamental precon- dition for a properly compatible worldwide nanoscale. There- fore, it is essential to create reliable embodiments of measures ✉ Fax: +49-531/592-5105, E-mail: peter.thomsen-schmidt@ptb.de and guidelines to be used for different measurement tech- niques like GIXR and XRF or SE and SFM. The content of this work is the manufacture and metrolog- ical characterisation of two different types of film thickness standards called X and E. The type X is a thin metal film on a quartz substrate, which is dedicated to X-ray techniques. Calibration of these standards is done by GIXR, which is also called X-ray reflectometry (XRR) in the literature; other pa- rameters proving the sample as a reference standard are also derived from these measurements. Film homogeneity is in- spected by XRF and GIXR. Ageing tests are still in progress. The type E is a thermally grown SiO 2 layer on a silicon chip, which is dedicated to ellipsometry. There is also a small struc- ture on the chip for step height measurement by SFM. Calibra- tion of film thickness is based also on GIXR measurements; step height calibration is made by a metrological SFM. 2 Manufacture of film thickness standards As the artefacts for both types of standards are completely different, they are manufactured in different insti- tutes using different technologies in order to achieve the best quality of material and proper process control. The type X is made in cooperation with the Institut für Oberflächenmod- ifizierung (IOM) and the Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS). The type E is manufactured in a con- ventional lithography process at the Institut für Mikroelek- tronik in Stuttgart. 2.1 Manufacture of standards for GIXR and XRF (type X) A fused silica substrate (SQ1, size: 60 mm × 20 mm × 10 mm) is polished mechanically to a roughness value R a of about 0.75 nm, measured by SFM within a scan area of 40 μ m × 40 μ m. Afterwards the surface is finished by ion beam planarisation to an R a value ranging between 0.14 and 0.27 nm. Details of the planarisation process are pub- lished elsewhere [1]. The standards consist of a Pt layer or a C–Ni–C system with nominal thickness values of 10 and 50 nm, respectively. The carbon coatings are protective layers with thickness values of about 2– 3 nm to prevent oxidation