Determination of optimal parameters for CD-SEM measurement of line-edge roughness

Bunday, Benjamin; Bishop, Michael; McCormack, Donald W.; Villarrubia, John S.; Vladár, András; Dixson, Ronald G.; Vorburger, Theodore V.; Orji, Ndubuisi G.; Allgair, John A.

doi:10.1117/12.535926

Cited by 71 publications

(42 citation statements)

References 7 publications

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“…The deposited lines are significantly thinner in width than the nominal CD, showing an average width of $45 nm, with a standard deviation of $10 nm, showing significant line edge roughness (LER). 12 Some of this LER can be attributed to the grain size in the poly-crystalline AlN membrane material. The edges of the lines in the SEMs of the etched oxide patterns shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Assessing the manufacturing tolerances and uniformity of CMOS compatible metamaterial fabrication

Musick

Wendt

Resnick

et al. 2018

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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The manufacturing tolerances of a stencil-lithography variant, membrane projection lithography, were investigated. In the first part of this work, electron beam lithography was used to create stencils with a range of linewidths. These patterns were transferred into the stencil membrane and used to pattern metallic lines on vertical silicon faces. Only the largest lines, with a nominal width of 84 nm, were resolved, resulting in 45 ± 10 nm (average ± standard deviation) as deposited with 135-nm spacing. Although written in the e-beam write software file as 84-nm in width, the lines exhibited linewidth bias. This can largely be attributed to nonvertical sidewalls inherent to dry etching techniques that cause proportionally larger impact with decreasing feature size. The line edge roughness can be significantly attributed to the grain structure of the aluminum nitride stencil membrane. In the second part of this work, the spatial uniformity of optically defined (as opposed to e-beam written) metamaterial structures over large areas was assessed. A Fourier transform infrared spectrometer microscope was used to collect the reflection spectra of samples with optically defined vertical split ring from 25 spatially resolved 300 × 300 μm regions in a 1-cm2 area. The technique is shown to provide a qualitative measure of the uniformity of the inclusions.

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Section: Resultsmentioning

confidence: 99%

Assessing the manufacturing tolerances and uniformity of CMOS compatible metamaterial fabrication

Musick

Wendt

Resnick

et al. 2018

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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“…We note that detailed mathematical descriptions of the PSD, HHCF, and SVL functions used here and the extraction of spatial parameters such as correlation length and roughness exponents from these functions can readily be found in the literature. References in this area specifically dealing with resist LER include [2][3][4]6]. As is typically done in the literature, we assume the line-edge residuals to be well described in terms of self-affine fractal scaling.…”

Section: Metric Extraction Accuracymentioning

confidence: 99%

“…[4], we assume noise in the measurement process to be represented as additive white Gaussian noise on the true edge position data. We can thus simply add Gaussian noise to the ideal model edge data from above and observe its effect on metric extraction characteristics.…”

Section: Noise Sensitivitymentioning

confidence: 99%

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Experimental and model-based study of the robustness of line-edge roughness metric extraction in the presence of noise

Naulleau

Cain

2007

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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As critical dimensions shrink, line edge and width roughness (LER and LWR) become of increasing concern. Crucial to the goal of reducing LER is its accurate characterization. LER has traditionally been represented as a single rms value. More recently the use of power spectral density (PSD), height-height correlation (HHCF), and σ versus length plots has been proposed in order to extract the additional spatial descriptors of correlation length and roughness exponent.Here we perform a modeling-based noise-sensitivity study on the extraction of spatial descriptors from line-edge data as well as an experimental study of the robustness of these various descriptors using a large dataset of recent extreme-ultraviolet exposure data. The results show that in the presence of noise and in the large dataset limit, the PSD method provides higher accuracy in the extraction of the roughness exponent, whereas the HHCF method provides higher accuracy for the correlation length. On the other hand, when considering precision, the HHCF method is superior for both metrics.

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“…͑11͒ does not calculate the true value ͑popu-lation variance of LWR͒ but contains the SEM-image-noise component. 37,38 In the case when a nonstochastic variation coexists as in this study, its variance is further added to the experimental value. To confirm this, we subtracted the aforedetermined variances of the first, second, and image-noise components from the experimental value obtained using Eq.…”

Section: B Variance Of Nonstochastic Lwrmentioning

confidence: 99%

Spectral analysis of line edge and line-width roughness with long-range correlation

Hiraiwa

Nishida

2010

Journal of Applied Physics

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Large-scale integrations (LSIs) are facing an ever-growing problem of device variability. One of the origins that cause the variability is line-width roughness (LWR) caused by line edge roughness (LER). Accurate characterization of the LWR plays an essential role in controlling the LWR. To do this, we report a methodology, named the “assembly method,” that enables to analyze LWR statistics beyond the conventional correlation length limit, basing on the previous “patchwork” method and recent discrete power spectral density (PSD) method. The methodology virtually assembles a long line by gathering line segments that are randomly scattered on a single line or equally processed different lines. The virtual lines are repeatedly assembled by randomly changing the combination of the segments and the order of the gathered segments while permitting overlaps of the segments between the assembled lines. Squared Fourier transforms of their widths are averaged over the assembled lines to obtain the PSD. By these steps, the statistical noise, which is inherent to experimental PSDs, is markedly reduced. Furthermore, to extract LWR statistics by comparing experimental and theoretical PSDs, we derived an analytic formula of the assembled-line PSD. In the derivation, the randomness of the segment collections played a key role. The PSDs calculated using the formula almost completely fitted experimental PSDs that were obtained by the assembly method. The parameters used in the best-fitted calculation revealed that the photoresist LWR of this study contained a component that had a correlation length of 2780 nm in addition to the previously reported LWR of 35 nm. The LWR variance of the component accounted for approximately 10% of the total variance. The formula also enabled us to evaluate the accuracy of experimentally obtained averages of widths. We find two distinct features in the PSDs by the assembly method. One is the oscillatory structure that shows up in the case when the correlation length is larger than half the length of the segments. A trace of this structure was actually observed in the experimental PSDs of this study. The other is the spikes that are periodically observed as a function of wave number. The spikes originate from a nonstochastic width variation that exists in all the segments in common. Their intensity is proportional to the number of gathered segments in the assembled lines. Because the spikes are excluded from the analysis, the LWR parameters determined by the assembly method are not affected by the nonstochastic variation, unlike the conventional methods. By all these results, we confirm that the assembly method of this study extends the upper limit of analyzable correlation lengths by a factor of approximately 20 and enhances the accuracy as well. This feature also has a practical significance that the widely observed LWR with a correlation length of approximately 35 nm can be analyzed by the assembly method using a conventional critical-dimension scanning-electron-microscope, without resorting to a specially designed one. Accordingly, the method will be a key tool for investigating LER and LWR in developing and manufacturing LSIs. It will also help analyze other stochastic processes in many research and development settings.

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Determination of optimal parameters for CD-SEM measurement of line-edge roughness

Cited by 71 publications

References 7 publications

Assessing the manufacturing tolerances and uniformity of CMOS compatible metamaterial fabrication

Assessing the manufacturing tolerances and uniformity of CMOS compatible metamaterial fabrication

Experimental and model-based study of the robustness of line-edge roughness metric extraction in the presence of noise

Spectral analysis of line edge and line-width roughness with long-range correlation

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