Comparison of line width calibration using critical dimension atomic force microscopes between PTB and NIST

Abstract

International comparisons between National Metrology Institutes are important to verify measurement results and the associated uncertainties. In this paper, we report a comparison of the line width calibration of a crystalline silicon line width standard, referred to as IVPS100-PTB standard, between the Physikalisch-Technische Bundesanstalt in Germany and the National Institute of Standards and Technology in the United States. Critical dimension atomic force microscopy was the measurement method used for this comparison. Both institutes applied generally the same but independently developed traceability pathways: the scaling factor of the atomic force microscope (AFM) scanner was calibrated by a set of step height and lateral standards certified by metrological AFMs, while the effective tip width was ultimately traceable to the lattice parameter of silicon via high resolution transmission electron microscopy. Good agreement has been achieved in the comparison: For two groups of line features with nominal critical dimensions (CDs) of 50 nm, 70 nm, 90 nm, 110 nm and 130 nm that were compared, the observed deviations of CD results were between −1.5 nm and 0.3 nm. The deviations are well within the associated measurement uncertainty.

Comparison of EUV Photomask Metrology Between CD-AFM and TEM

“…The results of state-of-the-art studies indicate that sub-nanometer measurement uncertainty can be reached for CD metrology using reference TEM method [18]. When the error propagation of all possible error sources in both realization and dissemination is considered, the expanded measurement uncertainty of CD metrology may reach about 0.7-1.6 nm using the methodology mentioned above, as confirmed in a bilateral comparison between the NIST and PTB [22].…”

Dimensional artefacts to achieve metrological traceability in advanced manufacturing

“…A similar approach for determination of single crystal silicon linewidth using high-resolution TEM imaging was followed by the PTB [62]. The results of the first comparison on silicon linewidth values at and below 100 nm showed agreement within the expanded measurement uncertainties, which were estimated at 0.7 nm [64]. The use of the single crystal silicon lattice as a secondary realisation of the metre for length measurements at the nanoscale has recently been recommended by the Consultative Committee for Length (CCL) of the International Committee for Weights and Measures (CIPM) [28].…”

Metrology for the next generation of semiconductor devices

“…In topography mode, AFM is less sensitive to materials’ differences and as such could be used for low-contrast materials such as those shown in Figure 1d or in probing memristor nanodevices 67 where it has been used to study the shape dependent performance of ribbed and planar TiO 2 structures 119 . AFMs can be made directly traceable to the SI length using displacement interferometry, or with calibrated samples 120-122 . See Fig.…”