EUV mask absorber characterization and selection

Yan, Pei-yang; Zhang, Guojing; Kofron, Patrick; Powers, Jeff; Tran, Mark; Liang, Ted; Stivers, Alan R.; Lo, Fu-Chang

doi:10.1117/12.392025

Cited by 25 publications

(20 citation statements)

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“…It has been demonstrated previously in the Si wafer format that TaN EUVL mask absorber in many areas are comparable to that of Cr absorbers, such as high chemical resistance to the mask cleaning, high etch selectivity to the buffer oxide 1 . In addition, TaN film has higher EUV absorbance than that of Cr film.…”

Section: Introductionmentioning

confidence: 94%

EUVL Square Mask Patterning with TaN Absorber

Yan

Huang

et al. 2002

SPIE Proceedings

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Using TaN as extreme ultra-violet lithography (EUVL) mask absorber has been previously explored in wafer format 1-2 . Due to substrate material difference between the square mask format and Si wafer format, e.g., electrical conductivity and thermal conductivity difference, etc., the etch process does not behave the same when mask substrate switches from the Si wafer to the square quartz substrates. With low thermal conductivity on quartz material and no backside cooling, mask etch prefers low power as compared to the Si wafer etch. In the study, we found that for a given source and bias power, the cooling of the substrate plays a role in TaN etch rate and selectivity to the buffer oxide layer.In this paper, we will present detailed study and comparison of TaN EUVL mask absorber etch characteristics for both the Si substrate and the square quartz substrate cases. The effect of source power, bias power, and backside cooling will also be discussed. The etchers used in study to etch TaN film on the wafer substrate and on the square format mask substrate have the similar configuration. With the optimized etch process, we have achieved good TaN etch profile with high etch selectivity to SiO 2 buffer layer on the square quartz mask substrate.

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Section: Introductionmentioning

confidence: 94%

EUVL Square Mask Patterning with TaN Absorber

Yan

Huang

et al. 2002

SPIE Proceedings

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“…EUV mask absorber requirements, etch process and cleaning durability have all been assessed for these materials. 8 TaN has been the leading candidate due to its processing compatibility as well as its high absorbance in the EUV regime. 9 Films that are more absorbent can be deposited thinner and can still attenuate radiation down to the process requirement.…”

Section: Mask Absorbermentioning

confidence: 99%

Longer wavelength EUV lithography (LW-EUVL)

Maloney

Smith

2012

SPIE Proceedings

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Extreme UV Lithography (EUVL) is generally accepted as the leading candidate for next generation lithography. Several challenges remain for EUVL, especially as its insertion point is pushed to finer resolution. Although diffractive scaling may suggest a transition to shorter EUVL wavelengths, several issues arise that would make that difficult. Challenges involve issues such as flare, multilayer (ML) bandwidth, and reflector throughput which tend to worsen with decreasing wavelength. In this study, we have evaluated the tradeoff between flare scaling effects and diffractive scaling effects for EUVL, where flare induced image degradation is likely to dominate as sub-13.5 nm wavelengths are considered. With surface scatter effects scaling as 1/λ 2 , the idea of longer wavelength (LW-EUVL) becomes interesting. Since a working wavelength is driven by the selection of ML materials (which are molybdenum and silicon for 13.5 nm), the identification of suitable alternatives is an initial challenge. We have optimized aluminum and various refractory metals at 17.2 nm and present results. The optimized combination of aluminum with yttrium, zirconium, and other metals result in theoretical reflectivity values above 75%. We also describe possibilities for alternative LW-EUVL sources for 17.2 nm operation as well as the impact on resist absorption, especially through halogens of higher molar absorption (such as fluorine). The impact on mask absorber materials is also presented, which may also exhibit increased absorbance, leading to a lowering of film thickness requirements.

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“…A large number of absorber and buffer layers were studied [5] [6] [7], particularly Cr and Ta-based materials (such as TaN, TaBN, TaSiN or TaGeN).…”

Section: Buffer Layermentioning

confidence: 99%

A new absorbing stack for EUV masks

et al. 2004

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Extreme Ultraviolet (EUV) masks are composed of EUV-reflective regions (multilayer) and of EUV-absorbing regions (patterned areas). The choice of materials for the absorbing stack (i.e. the buffer layer and the absorber layer) is crucial for providing good optical performances. This choice has to take into account three major issues: optical aspects (EUV and DUV performances, aerial image); repair feasibility and technological feasibility (deposition, etching, stripping…); ageing and utilization aspects: stability of the stack, cleaning capability.In this paper, a new absorbing stack A/B is proposed: this stack completely fulfils optical specifications and its total thickness is much lower than those found in the literature, with absorbing materials like TiN, Cr or TaN for instance. This thin thickness enables to reduce shadowing effects, which is particularly interesting for very advanced nodes.Experimental studies were then carried out on this new stack. We focused on two major topics: low temperature deposition and wet etching feasibility of B-material.

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EUV mask absorber characterization and selection

Cited by 25 publications

References 0 publications

EUVL Square Mask Patterning with TaN Absorber

EUVL Square Mask Patterning with TaN Absorber

Longer wavelength EUV lithography (LW-EUVL)

A new absorbing stack for EUV masks

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