Improvement of actinic blank inspection and phase defect analysis

Yamane, Takeshi; Tanaka, Toshihiko; Terasawa, Tsuneo; Suga, Osamu

doi:10.1117/12.864290

Cited by 9 publications

(5 citation statements)

References 12 publications

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“…Next we consider darkfield mask blank inspection [10,11]. In this case, the mask roughness again leads to speckle, but the final recorded speckle is at significantly lower contrast due to the camera pixel size being considerably larger than the speckle size.…”

Section: Darkfield Mask Blank Inspectionmentioning

confidence: 98%

Extreme ultraviolet mask roughness: requirements, characterization, and modeling

et al. 2014

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It is now well established that extremely ultraviolet (EUV) mask multilayer roughness can lead to wafer-plane line-edge roughness (LER) in lithography tools. It is also evident that this same effect leads to sensor plane variability in inspection tools. This is true for both patterned mask and mask blank inspection. Here we evaluate mask roughness specifications explicitly from the actinic inspection perspective. The mask roughness requirement resulting from this analysis are consistent with previously described requirements based on lithographic LER. In addition to model-based analysis, we also consider the characterization of multilayer mask roughness and evaluate the validity of using atomic force microscopy (AFM) based measurements by direct comparison to EUV scatterometry measurements as well as aerial image measurements on a series of high quality EUV masks. The results demonstrate a significant discrepancy between AFM results and true EUV roughness as measured by actinic scattering.

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Section: Darkfield Mask Blank Inspectionmentioning

confidence: 98%

Extreme ultraviolet mask roughness: requirements, characterization, and modeling

et al. 2014

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“…In the MIRAI-Selete's work, a technique for actinic inspection of EUVL mask blank utilizing dark-field imaging was developed with a 99% probability of detecting 1.2 nm-high and 40 nm-wide phase defect. 6,7 Also, the printed line patterns affected by the phase defects were examined, and depending on the exposure conditions the variations of the impacts of phase defects were investigated. Their simulation results showed the advantage of off-axis illumination in minizing the impact of phase defect.…”

Section: Introductionmentioning

confidence: 99%

Phase defect printability analyses: dependence of defect type and EUV exposure condition

Terasawa¹,

Yamane²,

Arisawa³

et al. 2012

SPIE Proceedings

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Phase defect printability and imaging characteristics were investigated by using aerial image simulation to clarify the phase defect impact on patterns depending on defect types, and on exposure conditions. In particular, the difference between the impacts caused by the same size bump phase defect and pit phase defect on 28 nm ~ 16 nm L&S projected patterns were investigated by calculating line width variations. Aerial images of phase defects in an absence of any absorber pattern were also calculated, and the image intensity losses of the two types of defects were compared. For a dipole illumination with 0.25 NA (numerical aperture) the pit phase defect impact was found to be stronger than the bump phase defect impact, when the two defect widths were less than 70% of the half-pitch of L&S patterns on the mask. This occurrence was not foreseen by the defect image calculation. On the other hand, for circular illumination with 0.33 NA, the bump defect impact was found to be stronger than the pit phase defect impact, which was consistent with the defect image calculation results. The contribution of dipole illumination in lowering the phase defect impact was confirmed for both bump and pit phase defects.

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“…Therefore, an actinic (at wavelength) defect inspection technique is being pursued. [1][2][3][4][5][6][7][8][9] To address this issue, a full-filed inspection prototype (MIRAI-tool) was developed by Selete [10][11][12][13][14][15][16][17] , and a HVM prototype tool is now under development by Lasertec and EIDEC. The defect detection probability of the full-field inspection prototype was found to be more than 99 % for a 1.2 nm-high 40 nm-wide defect with an inspection time of 4.8 hours for full-field area of a mask blank.…”

Section: Introductionmentioning

confidence: 99%

Improved signal to noise ratio in actinic EUVL mask blank inspection

Yamane¹,

Terasawa²

2012

SPIE Proceedings

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We have developed actinic inspection systems to detect multilayer phase-defects with dark field imaging. Although a prototype system for full-field inspection is available for half-pitch (hp) 16 nm node from the viewpoint of inspection sensitivity, but the inspection time for such a full-field area of a mask requires 4.8 hours and hence the technique is not viable for a high-volume manufacturing (HVM) application. To reduce the inspection time of the prototype, its signal to noise ratio was analyzed. The result shows that an "n" times faster scanning speed would require an "n" times enhancement of the illumination intensity for the system. The intensity was enhanced by 1.7 times, by improving the optic efficiency of the system where full-field inspection time reduced from 4.8 hours to 3.25 hours, and where the detection probability was also improved. These results are applied towards the development of a HVM prototype, and for evaluating 11 nm node inspection techniques.

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Improvement of actinic blank inspection and phase defect analysis

Cited by 9 publications

References 12 publications

Extreme ultraviolet mask roughness: requirements, characterization, and modeling

Extreme ultraviolet mask roughness: requirements, characterization, and modeling

Phase defect printability analyses: dependence of defect type and EUV exposure condition

Improved signal to noise ratio in actinic EUVL mask blank inspection

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