Determining the shape and periodicity of nanostructures using small-angle X-ray scattering

Abstract

The semiconductor industry is exploring new metrology techniques capable of meeting the future requirement to characterize three‐dimensional structure where the critical dimensions are less than 10 nm. X‐ray scattering techniques are one candidate owing to the sub‐Å wavelengths which are sensitive to internal changes in electron density. Critical‐dimension small‐angle X‐ray scattering (CDSAXS) has been shown to be capable of determining the average shape of a line grating. Here it is used to study a set of line gratings patterned via a self‐aligned multiple patterning process, which resulted in a set of mirrored lines, where the individual line shapes were asymmetric. The spacing between lines was systematically varied by sub‐nm shifts. The model used to simulate the scattering was developed in stages of increasing complexity in order to justify the large number of parameters included. Comparisons between the models at different stages of development demonstrate that the measurement can determine differences in line shapes within the superlattice. The shape and spacing between lines within a given set were determined to sub‐nm accuracy. This demonstrates the potential for CDSAXS as a high‐resolution nanostructure metrology tool.

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

“…SAXS (Sunday et al, 2015;Sunday et al, 2016) and electron microscopy (Villarrubia et al, 2015) measurements of the described samples are already reported in the literature. We use the line shape reconstructed from SAXS measurements by Sunday et al (Sunday et al, 2015) as a comparison for our GISAXS measurements.…”

“…Due to the multi-step production process, the grating lines rest on top of a layer structure consisting of 30 nm of silicon nitride on top of 25 nm of titanium nitride on top of 100 nm of silicon oxide, on the silicon wafer. Further details of the sample production have been published previously (Sunday et al, 2015;Villarrubia M Pflüger, RJ Kline, A Fernández Herrero, M Hammerschmidt, V Soltwisch, M Krumrey: Extracting Dimensional Parameters of Gratings Produced with Self-Aligned Multiple Patterning Using GISAXS et al, 2015). SAXS (Sunday et al, 2015;Sunday et al, 2016) and electron microscopy (Villarrubia et al, 2015) measurements of the described samples are already reported in the literature.…”

“…Further details of the sample production have been published previously (Sunday et al, 2015;Villarrubia M Pflüger, RJ Kline, A Fernández Herrero, M Hammerschmidt, V Soltwisch, M Krumrey: Extracting Dimensional Parameters of Gratings Produced with Self-Aligned Multiple Patterning Using GISAXS et al, 2015). SAXS (Sunday et al, 2015;Sunday et al, 2016) and electron microscopy (Villarrubia et al, 2015) measurements of the described samples are already reported in the literature. We use the line shape reconstructed from SAXS measurements by Sunday et al (Sunday et al, 2015) as a comparison for our GISAXS measurements.…”

“…For the reconstruction of the undisturbed line with nominally zero pitchwalk, the pitchwalk is fixed as zero, so that the width of the simulated unit cell is twice the pitch 2 = 64 nm. Motivated by prior knowledge about the production process and electron microscopic images of cross sections of similarly produced samples (Sunday et al, 2015), the lines are described using the line width, the line height, elliptic rounding of three of the four corners, a side wall angle of one of the sides, and the distance between the mirrored lines. The parameters are varied within predefined limits, the extent of these boundaries is shown in figure 5 b).…”

“…One technique which is considered for this purpose is critical dimension small-angle x-ray scattering in M Pflüger, RJ Kline, A Fernández Herrero, M Hammerschmidt, V Soltwisch, M Krumrey: Extracting Dimensional Parameters of Gratings Produced with Self-Aligned Multiple Patterning Using GISAXS transmission (CD-SAXS) or reflection grazing incidence (CD-GISAXS) geometry (Bunday et al, 2018). X-ray scattering probes the average structure with nm precision over a relatively large (µm 2 ) area (Jones et al, 2003;Sunday et al, 2015). A key problem of scattering in the transmission geometry is that high X-ray intensities and long measurement times are needed to penetrate the full sample (Bunday et al, 2018).…”