Photoresist cross-sectional shape change caused by scanning electron microscope-induced shrinkage

Ohashi, T.; Sekiguchi, Tomoko; Yamaguchi, Atsuko; Tanaka, J.; Kawada, Hiroki

doi:10.1117/1.jmm.14.3.034001

Cited by 12 publications

(14 citation statements)

References 23 publications

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“…The heights before and after EB exposure were calculated to be 95.6 nm and 82.5 nm, respectively, indicating that a shrinkage of 14 % had occurred. The decrease in height and the rounding of the top corners are consistent with the results of previous study [10].…”

Section: Changes In Sidewall Morphology Top Corner and Heightsupporting

confidence: 92%

“…The cause of this difference could not be clarified in this study; it is likely that the footing part, being in contact with the substrate, was affected by the forces from the contact surface. A more detailed investigation is required to clarify the cause by referring to a previous study [10], which investigated the cross-sectional shape of the pattern in EB-induced shrinkage. Next, the height changes were evaluated.…”

Section: Changes In Sidewall Morphology Top Corner and Heightmentioning

confidence: 99%

“…The SEM image reflects the shape information of the photoresist pattern after the original shape has been deformed. EB-induced shrinkage has been evaluated in previous works [8][9][10][11][12][13]. Measurement techniques that do not, in principle, cause EB-induced shrinkage, such as atomic force microscopy (AFM), are necessary for precise evaluation.…”

Section: Introductionmentioning

confidence: 99%

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Photoresist shrinkage observation by a metrological tilting-AFM

Kizu

Misumi

Hirai

et al. 2023

Metrology, Inspection, and Process Control XXXVII

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Scanning electron microscopy (SEM) is commonly used for line edge roughness (LER) measurement; however, it is difficult to achieve high-precision LER measurement of photoresists because exposure to an electron beam (EB) causes shrinkage of the materials. The differences in the 3D sidewall shape before and after shrinkage have not been investigated in detail. In this study, EB-induced photoresist shrinkage was observed by employing the atomic force microscopy with tip-tilting technique (tilting-AFM), which enables high-precision observation of the vertical sidewall of the pattern. In the experiment, the shrinkage deformation was observed by measuring the same photoresist pattern with the tilting-AFM before and after EB exposure (by SEM observation) on the pattern. The results show that the sidewall was smoothed by EB exposure. Further, the tendency of changes in LER (roughness parameters) was observed. This measurement technique can be used to better understand photoresist materials and to improve the LER measurement by SEM.

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Section: Changes In Sidewall Morphology Top Corner and Heightsupporting

confidence: 92%

Section: Changes In Sidewall Morphology Top Corner and Heightmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Photoresist shrinkage observation by a metrological tilting-AFM

Kizu

Misumi

Hirai

et al. 2023

Metrology, Inspection, and Process Control XXXVII

View full text Add to dashboard Cite

show abstract

“…The decrease in height and the rounding of the top corners are consistent with the results of a previous study. 10…”

Section: Resultsmentioning

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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“…Note that observation by SEM could cause damage, specifically, shrinkage of the resist patterns. 9,10 The damage can be reduced by decreasing the acceleration voltage and the number of electrons. 9 The emission current, the frame integration, and acceleration voltage were decreased to the extent in which the images were still observable.…”

Section: Methodsmentioning

confidence: 99%

Bayesian optimization-based estimation of effective reaction radius of chemically amplified resist in acid catalyzed deprotection reaction

Jin

Kozawa

2022

Photomask Technology 2022

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Chemically amplified resist realized the high sensitivity in semiconductor manufacture by utilizing the acid catalyzed deprotection reaction of protected polymer. One of the parameters reflecting the reaction ability of resist is effective reaction radius of deprotection (Rp). However, Rp cannot be achieved by experimental measurements. Similarly, the concentration of protected units at dissolving point of developer (Cth) cannot be measured as well. Cth strongly related to the generation of defects of resist pattern after development. In the previous study, a simulation model of electron beam (EB) lithography processes from beam exposure to development was constructed. To calibrate the EB lithography model, these parameters must be estimated. Resist pattern taken by scanning electron microscopy (SEM) was used to compare with the simulation calculated resist pattern. The difference between experimental and simulation data was used to evaluate the influence of Rp and Cth on the simulation model. However, during this estimating process, the simulation model must compute every time when Rp or Cth changes. This is time-consuming and the computational cost is high. To reduce the iterative computation, Bayesian optimization (BO) based on Gaussian process regression (GPR) with Matérn covariance kernel was applied to accelerate the optimal pace. BO can optimize the parameter globally and locate the value that worthiest to test. By using BO, the iterative calculation was magnificently reduced from 140 to 35. The probable values of Rp or Cth were found. Furthermore, to prove the ability of BO, the result was verified by grid search method.

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Photoresist cross-sectional shape change caused by scanning electron microscope-induced shrinkage

Cited by 12 publications

References 23 publications

Photoresist shrinkage observation by a metrological tilting-AFM

Photoresist shrinkage observation by a metrological tilting-AFM

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

Bayesian optimization-based estimation of effective reaction radius of chemically amplified resist in acid catalyzed deprotection reaction

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