Unbiased roughness measurements: Subtracting out SEM effects

Lorusso, Gian; Rutigliani, Vito; Roey, Frieda Van; Mack, Chris A.

doi:10.1016/j.mee.2018.01.010

Cited by 42 publications

(32 citation statements)

References 4 publications

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“…In a previous study, a new technique for producing unbiased estimates of roughness parameters was investigated. 5 It is based on the use of an analytical model for SEM scattering behavior that predicts linescans for a given feature geometry. Run in reverse, an inverse linescan model can be used for edge detection in such a way that SEM noise can be adequately measured and statistically subtracted from the roughness measurement, thus providing unbiased estimates of the roughness parameters.…”

Section: Introductionmentioning

confidence: 99%

Unbiased roughness measurements: Subtracting out SEM effects, part 2

Lorusso

Rutigliani

Roey

et al. 2018

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

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The measurement of roughness of small lithographic patterns is biased by noise in the scanning electron microscopes (SEMs) used to make the measurements. Unbiasing the roughness measurement requires the measurement and subtraction of the image noise based on its unique frequency behavior. Improvement to prior white noise removal is achieved by applying a pink noise model. This pink noise removal technique was applied to roughness measurements made with different electron doses (frames of integration), different operating voltages, and different generations of SEM tools. Effective noise removal to create accurate unbiased estimates of the roughness was achieved over a wider range of SEM tool parameter settings than has been previously achieved. As a result, unbiased roughness measurements can now be used to characterize and improve stochastic variability in semiconductor lithography and patterning.

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Section: Introductionmentioning

confidence: 99%

Unbiased roughness measurements: Subtracting out SEM effects, part 2

Lorusso

Rutigliani

Roey

et al. 2018

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

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“…However, as the resolution of LER measurement using SEM is degraded by instrumental noise, the PSD in the high-frequency region is biased (forming a flat noise floor) and causes error in the LER. The flat noise floor was corrected, and the result shows good reproducibility in the previous studies, [2][3][4] although the precision of the measurement of roughness parameters has not yet been investigated sufficiently. We confirm the noise level of the PSD and HHCF toward reference metrology of roughness parameters and preliminarily calculate the roughness parameters from HHCF.…”

Section: Scaling Analysis Of Lermentioning

confidence: 80%

“…4(c)] used for the PSD calculation, the flat noise floor of the PSD detected in the high-frequency region was several orders of magnitude lower than that of a typical SEM. [2][3][4] The variation of the PðkÞ increased at frequencies higher than 0.1 nm −1 . There was a peak at 0.259 nm −1 that corresponds to a wavelength of 3.86 nm.…”

Section: Scaling Analysis Of Lermentioning

confidence: 99%

“…However, the use of CD-SEMs to provide absolute LER measurements at the sub-nm scale is unreliable because of the difficulty of line-edge determination 1 and the random noise in the high-frequency region. [2][3][4] As the dimensions of semiconductor devices continue to decrease, the horizontal resolution of the SEM becomes insufficient. In addition, CD-SEM provides a top-view (twodimensional) metrology and cannot be used to measure a three-dimensional (3-D) profile of the vertical sidewall of a line pattern.…”

Section: Introductionmentioning

confidence: 99%

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Line edge roughness measurement on vertical sidewall for reference metrology using a metrological tilting atomic force microscope

Kizu

Misumi

Hirai

et al. 2020

J. Micro/Nanolith. MEMS MOEMS

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Line edge roughness (LER) measurement is one of the metrology challenges for three-dimensional device structures, and LER reference metrology is important for reliable LER measurements. For the purpose of LER reference metrology, we developed an LER measurement technique that can analyze LER distribution along the height of a line pattern, with high resolution and repeatability. A high-resolution atomic force microscopy (AFM) image of a vertical sidewall of a line pattern was obtained using a metrological tilting-AFM, which offers SI-traceable dimensional measurements. The tilting-tip was controlled with an inclined servo axis, and it scans the vertical sidewall along a line pattern with a high sampling density to enable an analysis of the LER height distribution at the sidewall. A horizontal cross-section of the sidewall shows sidewall roughness with sub-nm resolution. Power spectral density (PSD) analysis of the sidewall profile showed that the PSD noise in the high-frequency region was several orders of magnitude lower than the noise of typical scanning electron microscopy methods. AFM measurements were sequentially repeated three times to evaluate the repeatability of the LER measurement; results indicated a high repeatability of 0.07 nm evaluated as a standard deviation of LER at each height. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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“…Images for PSD analysis for DOE 2 and 3 were captured using a square scan, 1024×1024 pixels at 100K magnification. The same magnification in the X and Y axis may help to reduce across field distortion and provides more reliable PSD analysis [6]. Table 1.…”

Section: Wafer Coating and Lithographic Evaluationmentioning

confidence: 99%

Utilizing Roughness Power Spectral Density Variables to Guide Resist Formulation and Understand Impact of Frequency Analysis through Process

Cutler¹,

Lee²,

Thackeray³

et al. 2018

J. Photopol. Sci. Technol.

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Linewidth roughness (LWR) remains a difficult challenge for improvement in all resist materials. In this paper, we intend to focus on the impact of key components of LWR by analyzing the power spectral density (PSD) curves which can be obtained using Fractilia's MetroLER computational software. We will study systematic changes to ArF resist formulations and correlate these changes with the overall PSD curves. In this manner we will use frequency analysis information to guide resist formulation improvements. We will also investigate the relationship between frequency roughness components and LWR through lithographic / etch processing and demonstrate which components correspond with the largest impact. In order to achieve quality data over low and high frequency ranges we changed our standard metrology setup to capture longer lines. By making systematic changes to the ArF resists, we can determine the key impacts of various controllable resist factors on the PSD. Through systematic analysis, we can deconvolute LWR improvements both after develop and after an etch process.

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Unbiased roughness measurements: Subtracting out SEM effects

Cited by 42 publications

References 4 publications

Unbiased roughness measurements: Subtracting out SEM effects, part 2

Unbiased roughness measurements: Subtracting out SEM effects, part 2

Line edge roughness measurement on vertical sidewall for reference metrology using a metrological tilting atomic force microscope

Utilizing Roughness Power Spectral Density Variables to Guide Resist Formulation and Understand Impact of Frequency Analysis through Process

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