Vendor capability for low-thermal-expansion mask substrates for EUV lithography

Blaedel, Kenneth L.; Taylor, John S.; Hector, Scott Daniel; Yan, Pei-yang; Ramamoorthy, Arun; Brooker, Peter

doi:10.1117/12.472273

Cited by 8 publications

(5 citation statements)

References 10 publications

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“…Blaedel at al. 10 summarize the results of these evaluations in more detail. Some substrates from one supplier have met the surface roughness requirement with 0.15 to 0.17 nm rms surface roughness.…”

Section: Mask Substratesmentioning

confidence: 98%

“…One measurement on a substrate from one supplier showed ~1 mrad rms local slope error compared to the target of <1 mrad total. Furthermore, Blaedel et al 10 detail some of the metrology challenges for verifying flatness. Measuring the surface flatness of each surface on an optical flat is challenging, but commercial instruments are becoming available to make these measurements.…”

Section: Mask Substratesmentioning

confidence: 99%

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EUVL masks: requirements and potential solutions

Hector

2002

Emerging Lithographic Technologies VI

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Extreme ultraviolet lithography (EUVL) is a leading next generation lithography technology. Significant progress has been made in developing mask fabrication processes for EUVL. The mask blank for EUVL consists of a low thermal expansion material substrate having a square photomask form factor that is coated with Mo/Si multilayers. A SEMI standard is now available for mask substrates. SEMI standards are also being developed for mask mounting, for mask blank multilayers and absorbers and for mask handling and storage. Several commercial suppliers are developing polishing processes for LTEM substrates, and they are progressing toward meeting the requirements for flatness, surface roughness, and defects defined in the SEMI standard.One of the challenges in implementing EUVL is to economically fabricate multilayer-coated mask blanks with no printable defects. Significant progress has been made in developing mask blank multilayer coating processes with low added defect density. Besides lowering added defect density, methods to reduce defect printability are being developed to effectively enable repair of many defect types. These repair processes might significantly increase yield of EUV mask blanks before defect density is lowered to production targets. Calculations of EUVL mask cost indicate that defect repair processes could allow the initial defect density targets for mask blanks to be relaxed.The mask patterning process for EUVL is nearly the same as that for conventional binary optical lithography masks. EUVL mask patterning efforts are focused on developing the EUV-specific aspects of the patterning process. Eight absorbers have been evaluated against the requirements for EUVL masks, and two absorbers-TaN and Cr--will probably meet the requirements after some further development.

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Section: Mask Substratesmentioning

confidence: 98%

Section: Mask Substratesmentioning

confidence: 99%

EUVL masks: requirements and potential solutions

Hector

2002

Emerging Lithographic Technologies VI

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“…For production qualification, SEMI Standard P37 3 currently specifies that the front and backside have a maximum of 50 nm p-v flatness over the 142 mm × 142 mm quality area. Currently, a typical value for the freestanding flatness of low thermal expansion material mask substrates is about 250 nm p-v. 4 The ability of the chuck to flatten a "standard" reticle depends primarily on the mechanical stiffness of the chuck and the clamping pressure. However, a thinner reticle would have a lower effective stiffness and therefore would be easier to flatten during electrostatic chucking.…”

Section: Chucking Effectsmentioning

confidence: 99%

Optimization of EUVL reticle thickness for image placement accuracy

et al. 2003

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Extreme ultraviolet lithography (EUVL) is one of the leading candidates for next-generation lithography in the sub-65 nm regime. The International Technology Roadmap for Semiconductors proposes overlay error budgets of 18 nm and 13 nm for the 45 nm and 32 nm nodes, respectively. Full three-dimensional finite element (FE) models were developed to identify the optimal mask thickness to minimize image placement (IP) errors. Five thicknesses of the EUVL reticle have been investigated ranging from 2.3 mm to 9.0 mm.The mask fabrication process was simulated, as well as the e-beam mounting, pattern transfer, and exposure mounting, utilizing FE structural models. Out-of-plane distortions and in-plane distortions were tracked for each process step. Both electrostatic and 3-point mounts were considered for the e-beam tool and exposure tool. In this case, increasing the thickness of the reticle will reduce the magnitude of the distortions.The effect of varying the reticle thickness on chucking was also studied. FE models were utilized to predict how changing the reticle thickness would affect the overall clamping response. By decreasing the reticle thickness (and therefore the effective bending stiffness), the deformed reticle is easier to flatten during chucking.In addition, the thermomechanical response of the reticle during exposure was investigated for different reticle thicknesses. Since conduction to the chuck is the main heat dissipation mechanism, decreasing the reticle thickness results in more energy being conducted away from the reticle, which reduces the maximum temperature rise and the corresponding thermal distortion.The FE simulations illustrate the optimal thickness to keep IP errors within the allotted error budget as well as provide the necessary flatness during typical chucking procedures.

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“…Additionally, the defect metrology techniques for both uncoated and coated mask blanks have difficulty in isolating the sources of the defects 10,11 . Additionally, the defect metrology techniques for both uncoated and coated mask blanks have difficulty in isolating the sources of the defects 10,11 .…”

Section: Inclusions Vs Defectsmentioning

confidence: 99%

“…As previously mentioned, multiple defects are being detected on each substrates 10,11,13 , however their source has not been explicitly identified. If these defects were the result of internal inclusions manifesting themselves on the surface, then large defect densities or large defect sizes should be present.…”

Section: Inclusions Vs Defectsmentioning

confidence: 99%

Characterization and characteristics of a ULE glass tailored for EUVL needs

Hrdina

Hanson

Fenn

et al. 2002

Emerging Lithographic Technologies VI

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The EUVL industry has unique material requirements, which are being addressed. Implementation of metrology methods new to ULE  Glass will be discussed along with material characteristics altered to meet the needs of EUVL. Metrology methods include multiple means of evaluating the striae, CTE and inclusions. Material characteristics have been altered to better meet the demands of the industry. The reduction in inclusion levels along with other improvements such as in the area of striae will be discussed here. Improvements of greater than 4x were achieved in these preliminary striae reduction trials.

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Vendor capability for low-thermal-expansion mask substrates for EUV lithography

Cited by 8 publications

References 10 publications

EUVL masks: requirements and potential solutions

EUVL masks: requirements and potential solutions

Optimization of EUVL reticle thickness for image placement accuracy

Characterization and characteristics of a ULE glass tailored for EUVL needs

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