Characterization and characteristics of a ULE glass tailored for EUVL needs

Hrdina, Kenneth E.; Hanson, B.; Fenn, Philip M.; Sabia, Robert

doi:10.1117/12.472321

Cited by 28 publications

(17 citation statements)

References 12 publications

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“…These measurements have been detailed previously [3,4]. What is measured can be a complex set of striae with different magnitudes.…”

Section: Measuring and Characterizing Striaementioning

confidence: 99%

Corning ULE glass can meet P-37 specifications

Rosch¹,

Beall²,

Maxon³

et al. 2007

SPIE Proceedings

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Corning ULE ® glass is a binary SiO 2 + TiO 2 composition formed directly using a flame hydrolysis process. ULE possesses a very low thermal expansion range that can also be accurately adjusted for various applications including EUV photolithography. For ULE to be used for mask blanks and optics applications, it is also necessary that the material be capable of meeting stringent flatness and roughness specifications. For ULE, small compositional striations have been shown to affect the surface quality by inducing mid-spatial frequency roughness during polishing. Therefore, the main challenge has been to reduce mid-spatial frequency roughness to an acceptably low level by diminishing compositional striations present in the glass.Recently, a combination of predictive modeling and experimentation has resulted in a process that reduces striae to the levels needed for EUV masks and optics. These models have enhanced the fundamental understanding of the glass forming process, leading to process adjustments both in oscillation patterns and additional thermal treatments producing glass with improved striae characteristics.ULE masks with reduced striae have been polished to mid-spatial frequency roughness peak-to-valley levels of less than 8 nm. This sub-8 nm topography accounts for less than 20% of the total 50 nm flatness error budget allowable for EUVL masks. These results indicate that Corning's ULE product can meet the P-37 surface finishing specifications, and combined with ULE's superior CTE performance is positioned as the material of choice for EUV mask blanks.

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“…These measurements have been detailed previously [3,4]. What is measured can be a complex set of striae with different magnitudes.…”

Section: Measuring and Characterizing Striaementioning

confidence: 99%

Corning ULE glass can meet P-37 specifications

Rosch¹,

Beall²,

Maxon³

et al. 2007

SPIE Proceedings

Self Cite

View full text Add to dashboard Cite

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“…It has been reported that striae are formed in TiO 2 -SiO 2 glass during the fabrication process and their periodicity is approximately 160 µm. 2 We prepared two types of specimen substrates cut from the ingot with the striae plane perpendicular to the z axis, as shown in Fig. 1(a), to investigate a evaluation method of striae in section 4.1; the substrate surfaces were parallel (specimen 1) and perpendicular (specimen 2) to the striae plane, as shown in Figs.…”

Section: Specimensmentioning

confidence: 99%

“…However, the TiO 2 -SiO 2 glasses have periodic striae (variation in TiO 2 concentration) associated with its fabrication process. 2 To fabricate homogeneous ultra-lowexpansion glasses for EUVL system, it is necessary to evaluate the striae accurately, and to feed back the measurement results to improvement of the glass production conditions.…”

Section: Introductionmentioning

confidence: 99%

Striae evaluation of TiO 2 -SiO 2 ultra-low expansion glasses using the line-focus-beam ultrasonic material characterization system

2006

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Super accurate evaluation method for TiO 2 -doped SiO 2 ultra-low-expansion glass having periodic striae associated with its fabrication process was investigated using the line-focus-beam ultrasonic material characterization (LFB-UMC) system. To obtain absolute values of leaky surface acoustic wave (LSAW) velocities measured with the LFB-UMC system, proper standard specimens of the glass for system calibration was examined. Using a specimen with a surface perpendicular to the striae plane as the standard specimen, a reliable standard LSAW velocity of 3308.18 m/s within ±0.35 m/s for the calibration was obtained regardless of influence of velocity variations due to the periodic striae. Also, we determined the accurate relationship between the TiO 2 concentrations and LSAW velocities (sensitivity: -0.0601 wt%/(m/s)) so that the TiO 2 concentration of the standard specimen with a LSAW velocity of 3308.18 m/s was determined to be 7.09 wt%. Furthermore, to evaluate more reliably the more homogeneous ultra-low-expansion glasses in the near future, the measurement accuracy of the LSAW velocity was improved with a method using the LFB device with a larger curvature radius R operating at lower frequency from ±0.0053% for R=1.0 mm at 225 MHz to ±0.0020% for R=2.0 mm at 75 MHz.

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“…Classes of mean CTE and its spatial uniformity are described in the standard, and commercial suppliers of bulk substrate material can probably meet at least <20 ppb/K requirements. 7,8 The temperature of operation of the EUVL mask must be specified because coefficient of thermal expansion changes with temperature. Measurement of CTE to the tolerances required by SEMI P37-1101 is challenging, and suppliers are developing methods with the required accuracy, precision and spatial resolution.…”

Section: Mask Substratesmentioning

confidence: 99%

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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Characterization and characteristics of a ULE glass tailored for EUVL needs

Cited by 28 publications

References 12 publications

Corning ULE glass can meet P-37 specifications

Corning ULE glass can meet P-37 specifications

Striae evaluation of TiO 2 -SiO 2 ultra-low expansion glasses using the line-focus-beam ultrasonic material characterization system

EUVL masks: requirements and potential solutions

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