Line edge roughness metrology: recent challenges and advances toward more complete and accurate measurements

Constantoudis, Vassilios; Papavieros, George; Lorusso, Gian; Rutigliani, Vito; Roey, Frieda Van; Gogolides, Εvangelos

doi:10.1117/1.jmm.17.4.041014

Cited by 6 publications

(9 citation statements)

References 33 publications

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“…BCP line roughness is an important performance metric for applying DSA to semiconductor manufacturing and lithography, 38,39 and therefore, we quantified the effect of the introduction of the homopolymer inks on the line roughness. Figure 5a shows an example power spectral density (PSD) profile of the PS line placement roughness (LPR) for the various DSA conditions: DSA versus SRSA and thin versus 40 At low frequencies (below 0.02 nm −1 , which corresponds to length-scales above 50 nm), the placement fluctuations plateau as a direct result of the guiding properties of the underlying pattern (Figure 5a).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Sequential Brush Grafting for Chemically and Dimensionally Tolerant Directed Self-Assembly of Block Copolymers

Chang

Loo

et al. 2022

ACS Appl. Mater. Interfaces

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We report a method for the directed self-assembly (DSA) of block copolymers (BCPs) in which a first BCP film deploys homopolymer brushes, or “inks”, that sequentially graft onto the substrate’s surface via the interpenetration of polymer molecules during the thermal annealing of the polymer film on top of existing polymer brushes. By selecting polymer “inks” with the desired chemistry and appropriate relative molecular weights, it is possible to use brush interpenetration as a powerful technique to generate self-registered chemical contrast patterns at the same frequency as that of the domains of the BCP. The result is a process with a higher tolerance to dimensional and chemical imperfections in the guiding patterns, which we showcase by implementing DSA using homopolymer brushes for the guiding features as opposed to more robust cross-linkable mats. We find that the use of “inks” does not compromise the line width roughness, and the quality of the DSA as a lithographic mask is verified by implementing a robust “dry lift-off” pattern transfer.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Sequential Brush Grafting for Chemically and Dimensionally Tolerant Directed Self-Assembly of Block Copolymers

Chang

Loo

et al. 2022

ACS Appl. Mater. Interfaces

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“…In the roughness analysis, this study adopts the self-affine fractal model 1,18,21,22 whose autocorrelation function RðrÞ is represented by three roughness parameters [standard deviation (σ), correlation length (ξ), and roughness exponent (α)], as follows:…”

Section: Change Of Sidewall Roughness Profile and Ler Analysismentioning

confidence: 99%

“…Height-height correlation function (HHCF) and power spectral density (PSD) are often used to evaluate self-affine fractals. 1,21,22 Figure 4 presents the HHCF and PSD calculated based on the sidewall profiles, as shown in Fig. 3.…”

Section: Change Of Sidewall Roughness Profile and Ler Analysismentioning

confidence: 99%

Evaluation of the change in photoresist sidewall roughness due to electron beam-induced shrinkage using atomic force microscopy

Kizu,

Misumi,

Hirai

et al. 2023

J. Micro/Nanopattern. Mats. Metro.

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.BackgroundScanning electron microscopy (SEM) is commonly employed for line edge roughness (LER) measurements; however, achieving high-precision LER measurement of photoresists is difficult through this approach because electron beam (EB) exposure causes shrinkage of materials. Moreover, the differences in the 3D sidewall shape before and after shrinkage have not been investigated in detail.AimEvaluation of the impact of photoresist shrinkage induced by EB exposure on the sidewall roughness of a pattern.ApproachThe shrinkage was observed by measuring a photoresist pattern before and after EB exposure using atomic force microscopy with a tip-tilting technique (tilting-AFM).ResultsEB exposure smoothed the surface roughness, rounded the top corners, and reduced the pattern height. Roughness parameters evaluated via LER analysis showed that with shrinkage, the standard deviation (σ) and roughness exponent (α) decreased, while the correlation length (ξ) increased.ConclusionsThe results show that SEM-based LER measurements may lead to underestimation of σ and α, and the overestimation of ξ because of the effect of EB-induced shrinkage. Overall, we establish a tilting-AFM technique to evaluate the 3D shape of photoresist patterns without EB damage and with high resolution and low noise.

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“…To address this issue, previous studies have investigated the impact of noise on roughness profiles using the power spectral density (PSD) and the height-height correlation function (HHCF) and have developed noise-correction techniques applicable to LER analysis. The corrected results are called unbiased PSD/HHCF [6,12,13]. Although these noise-correction techniques improve the reproducibility and reliability of roughness measurements, their assumptions partially neglect theoretical considerations on the noise-error component.…”

Section: Introductionmentioning

confidence: 99%

“…However, the validity of this assumption has not been checked, and the influence of the correlated component must be clarified for reliable assessment of noise errors. Some previous studies have similarly ignored the correlated component [6,13,[17][18][19][20][21][22]. As the above assumption is widely accepted in fields of roughness measurement, an accurate theoretical equation related to the noise error is imminently required for roughness analysis.…”

Section: Introductionmentioning

confidence: 99%

Effect of white noise on roughness measurements of self-affine fractals

Kizu

Misumi

Hirai³

et al. 2023

Meas. Sci. Technol.

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This study formulated and clarified the presentation of the noise-related error terms in the power spectral density (PSD) and height–height correlation function (HHCF) through a roughness analysis of self-affine fractals. Assuming the noise as white noise, this study simulated the PSD and HHCF of the noisy roughness profile in a typical situation: line-edge roughness measurements involved in semiconductor lithography technology. It was found that conventional noise-correction techniques can bias the PSD/HHCF from those of the true roughness profiles because they do not account for the residual noise-induced error. The findings obtained from the roughness analysis and simulation techniques are expected to benefit various applications, such as clarifying the quantitative residual error in specific situations, selecting the optimum analysis method (PSD or HHCF), estimating the required number of averaged profiles (measurements) that yields sufficiently small noise errors, and considering strategies for noise reduction.

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Line edge roughness metrology: recent challenges and advances toward more complete and accurate measurements

Cited by 6 publications

References 33 publications

Sequential Brush Grafting for Chemically and Dimensionally Tolerant Directed Self-Assembly of Block Copolymers

Sequential Brush Grafting for Chemically and Dimensionally Tolerant Directed Self-Assembly of Block Copolymers

Evaluation of the change in photoresist sidewall roughness due to electron beam-induced shrinkage using atomic force microscopy

Effect of white noise on roughness measurements of self-affine fractals

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