EUVL mask blank repair

Barty, Anton; Mirkarimi, Paul B.; Stearns, D. G.; Sweeney, Donald W.; Chapman, Henry N.; Clift, W. Miles; Hector, Scott Daniel; Yi, Moonsuk

doi:10.1117/12.472313

Cited by 13 publications

(13 citation statements)

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“…28 To result in <±1% relative reflectivity uniformity error, the mask multilayer must be coated so that film thickness mean error and uniformity error must be <±0.15% of the target film thickness. As reported by Hector et al, 24 a mask coating process has been developed that provides relative reflectivity variation from all sources of ±0.41% 3σ, which significantly exceeds the minimum requirement of <±1% 3σ. Recently, this coating uniformity has been achieved with the same process used to maximize multilayer defect smoothing as described by Mirkarimi et al 19 Hector et al referenced previous efforts to redesign the multilayer coating recipe to provide larger bandwidth, but Kuhlmann et al 29 recently started design and fabrication of coatings with greater bandwidth and with less change in reflectivity with wavelength.…”

Section: Multilayer Coating Reflectivitymentioning

confidence: 97%

“…Defects at or near the surface might be removed with wet cleaning processes. Barty et al 24 have developed and demonstrated a technique to remove particle defects at or near the surface of the multilayer by using focused ion beam milling. Figure 6 depicts their approach.…”

Section: Multilayer Defect Repairmentioning

confidence: 99%

“…Hector et al 24 proposed a roadmap for relative reflectivity uniformity error due to the mask and for mask multilayer reflectivity uniformity. This roadmap has also been incorporated into the requirement for EUV masks shown in the 2001 update to the ITRS.…”

Section: Multilayer Coating Reflectivitymentioning

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: Multilayer Coating Reflectivitymentioning

confidence: 97%

Section: Multilayer Defect Repairmentioning

confidence: 99%

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EUVL masks: requirements and potential solutions

Hector

2002

Emerging Lithographic Technologies VI

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“…The main reason why it is needed is to boost the yield of mask blanks. A couple of repair methods have been suggested [3] [5] [14][15]. An amplitude defect in several Mo/Si pairs can be scooped out by FIB or RAVE, although a crater remains afterward.…”

Section: Effect Of Defect Repair On Aerial Imagementioning

confidence: 99%

Lithographic characterization of EUVL mask blank defects

et al. 2004

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The strong smoothing effect resulting from recent progress in multilayer deposition technology has a great influence on the imaging characteristics of mask blank defects. The imaging characteristics of such defects were investigated through accurate simulations employing the FDTD method; and the effect of multilayer smoothing on the aerial image was examined. Strong smoothing was found to suppress the degradation in the aerial image due to phase defects while at the same time giving rise to phase defects that are undetectable with a visible-light inspection tool. 3-dimensional simulations also indicated the existence of such defects. Moreover, the aerial image of phase defects after repair with an electron beam was also investigated. Repair was found to be effective when there was no smoothing, but not so effective when there was strong smoothing. Experimental verification ofthese results will be attempted in the near future.

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“…However, there are currently no known commercial technologies for repair of defects in the ML coating, even though several approaches 4,5 have been proposed. One approach to mitigating the phase defect problem in EUVL mask blanks is a defect-smoothing technique.…”

Section: Introductionmentioning

confidence: 99%

At-wavelength inspection of defect smoothing in EUVL masks

Park

Mirkarimi

et al. 2002

Emerging Lithographic Technologies VI

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Results of at-wavelength inspection of EUVL mask substrate defects which were smoothed using multilayer coatings are presented. Programmed mask substrate defects were made with 80nm gold (Au) spheres, which were deposited on the mask substrate before the Mo/Si reflective multilayer coating. After coating, at-wavelength and visible-light inspection of the mask substrates were performed. The smoothing process was found to be effective in significantly suppressing the EUV visibility of the defects.

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EUVL mask blank repair

Cited by 13 publications

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EUVL masks: requirements and potential solutions

EUVL masks: requirements and potential solutions

Lithographic characterization of EUVL mask blank defects

At-wavelength inspection of defect smoothing in EUVL masks

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