Characterization of the shape and line-edge roughness of polymer gratings with grazing incidence small-angle X-ray scattering and atomic force microscopy

Abstract

Grazing-incidence small-angle X-ray scattering (GISAXS) is increasingly used for the metrology of substrate-supported nanoscale features and nanostructured films. In the case of line gratings, where long objects are arranged with a nanoscale periodicity perpendicular to the beam, a series of characteristic spots of high-intensity (grating truncation rods, GTRs) are recorded on a twodimensional detector. The intensity of the GTRs is modulated by the threedimensional shape and arrangement of the lines. Previous studies aimed to extract an average cross-sectional profile of the gratings, attributing intensity loss at GTRs to sample imperfections. Such imperfections are just as important as the average shape when employing soft polymer gratings which display significant line-edge roughness. Herein are reported a series of GISAXS measurements of polymer line gratings over a range of incident angles. Both an average shape and fluctuations contributing to the intensity in between the GTRs are extracted. The results are critically compared with atomic force microscopy (AFM) measurements, and it is found that the two methods are in good agreement if appropriate corrections for scattering from the substrate (GISAXS) and contributions from the probe shape (AFM) are accounted for.

Applicability of the Debye-Waller damping factor for the determination of the line-edge roughness of lamellar gratings

“…In the presence of roughness, light is scattered out of the position of the diffraction orders and several scattering phenomena can be observed 10,12,32,33 . The total intensity of the out-scattered light depends on the amplitude of the roughness.…”

Extracting dimensional parameters of gratings produced with self-aligned multiple patterning using grazing-incidence small-angle x-ray scattering

“…Despite these challenges, GISAXS was already shown to be a suitable method to determine line grating pitches (Yan and Gibaud, 2007;Wernecke et al, 2014b) and line profiles (Hofmann, Dobisz, and Ocko, 2009;Soltwisch et al, 2017;Yamanaka et al, 2016) as well as line-edge roughness (Suh et al, 2016). It was also used to reconstruct the average profile of contact holes (Hagihara et al, 2017), to unravel complex hierarchical nanostructures (Khaira et al, 2017) and to quantify deviations in nanostructure orientation (Pflüger et al, 2019).…”

Estimation of Line Cross Sections Using Critical-Dimension Grazing-Incidence Small-Angle X-Ray Scattering

“…Grazing Incidence Small Angle X-ray Scattering (GISAXS) is mostly used for the characterization of thin film morphologies, but has been recently used to approximate the profile of polymer line gratings [13]. A precise alignment of the lines in the direction of the incoming beam is required to record a semicircle of spots, which are laid out as the intersection of the Ewald sphere with the Bragg rods from the gratings [14,15].…”

“…To do so, Hoffman et al proposed to rotate the gratings along the normal of the substrate to record the full Bragg rods [16]. Later on, Suh et al proposed to record GISAXS images at several incident angles to probe the form factor of the line profile across different regions of reciprocal space [13]. In parallel, development improving data analysis progressed.…”

“…Transmission scattering in grazing-incidence geometry, called GT-SAXS, were studied to get rid of the complexity of the distorted-wave Born approximation (DWBA) formalism [17]. A proposed a model to extract the roughness of line gratings with a combination of AFM and GISAXS [13].…”