Impact of EUV photomask line-edge roughness on wafer prints

Qi, Zhengqing John; Gallagher, Emily; Negishi, Yoshiyuki; McIntyre, Gregory; Zweber, Amy E.; Senna, Tasuku; Akutagawa, Shinichi; Konishi, Toshio

doi:10.1117/12.976855

Cited by 7 publications

(6 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Crystallinity however, is very likely to impair surface roughness and etch bias. Preferential etching along crystal grains can cause increased absorber line edge roughness (LER) and lead to critical dimension (CD) variations, which will be transferred to wafer [27,28]. Additionally, absorber morphology affects mechanical film stress.…”

Section: Film Morphologymentioning

confidence: 99%

Ni-Al Alloys as Alternative EUV Mask Absorber

et al. 2018

View full text Add to dashboard Cite

Extreme ultraviolet (EUV) lithography is being industrialized as the next candidate printing technique for high-volume manufacturing of scaled down integrated circuits. At mask level, the combination of EUV light at oblique incidence, absorber thickness, and non-uniform mirror reflectance through incidence angle, creates photomask-induced imaging aberrations, known as mask 3D (M3D) effects. A possible mitigation for the M3D effects in the EUV binary intensity mask (BIM), is to use mask absorber materials with high extinction coefficient κ and refractive coefficient n close to unity. We propose nickel aluminide alloys as a candidate BIM absorber material, and characterize them versus a set of specifications that a novel EUV mask absorber must meet. The nickel aluminide samples have reduced crystallinity as compared to metallic nickel, and form a passivating surface oxide layer in neutral solutions. Composition and density profile are investigated to estimate the optical constants, which are then validated with EUV reflectometry. An oxidation-induced Al L2 absorption edge shift is observed, which significantly impacts the value of n at 13.5 nm wavelength and moves it closer to unity. The measured optical constants are incorporated in an accurate mask model for rigorous simulations. The M3D imaging impact of the nickel aluminide alloy mask absorbers, which predict significant M3D reduction in comparison to reference absorber materials. In this paper, we present an extensive experimental methodology flow to evaluate candidate mask absorber materials.

show abstract

Section: Film Morphologymentioning

confidence: 99%

Ni-Al Alloys as Alternative EUV Mask Absorber

et al. 2018

View full text Add to dashboard Cite

show abstract

“…The correlation length slightly increases with the jog step but it is not impacted by the jog amplitude. The cut-off frequency for a quadrupole source is shown in the equations below [2,6]. Mask LER below fmin should be completely transferred to wafer LER, while the mask LER above fmax should be completely filtered out.…”

Section: Wafer Print and Comparison With Mask Resultsmentioning

confidence: 99%

“…The wafer line edge roughness (LER) and line width roughness (LWR) are attracting increasing concern as CDs decrease [1][2][3][4]. The wafer LER is not only a resist-driven effect.…”

Section: Introductionmentioning

confidence: 99%

EUV lithography: LER design, mask, and wafer impact

Wang,

Gallagher,

Trivkovic

et al. 2024

Optical and EUV Nanolithography XXXVII

View full text Add to dashboard Cite

The line edge roughness (LER) of the mask absorber increases as the critical dimension (CD) approaches the mask's imaging limit. Mask LER has an impact on the corresponding wafer LER, especially in the case of EUV lithography because of the inverse dependence on exposure wavelength. Low-frequency mask LER is transferred directly to the wafer LER while high-frequency mask LER impacts the wafer image by reducing the image log slope (ILS). In this study, we designed a programmed random LER module and fabricated it on a state-of-the-art EUV mask to introduce controlled variations in LER amplitude while maintaining a similar spatial frequency to the reference mask LER. The unbiased 3-σ mask LER was extracted from the 36nm pitch line/space design, showing that programmed LER is transferred to mask LER. The mask was exposed with the ASML NXE:3400B EUV lithography scanner under focus exposure matrix (FEM) conditions. The transfer of mask LER to wafer LER exhibited a similar trend in programmed jog amplitude and step. Wafer LER increases when the exposure conditions deviate from the best dose or best focus, as the mask error enhancement factor (MEEF) increases and is proportional to the LER transfer function. It was observed that programmed LER is filtered through the illumination system, by comparing the power spectral density (PSD) of mask and wafer LER. The programmed LER led to increased wafer defects, specifically, wafer 3-σ unbiased LER above 2.4nm starts to increase wafer defects.

show abstract

“…As extreme ultraviolet (EUV) lithography [1][2][3][4] continues to move towards high-volume manufacturing (HVM), photomask blank defectivity has remained a persistent obstacle. 5 Recent efforts have limited blank defects greater than 54 nm in size, 6 however much experimental work have shown that smaller defects also requires elimination.…”

Section: Introductionmentioning

confidence: 99%

Defect avoidance for EUV photomask readiness at the 7 nm node

Rankin

Narita

et al. 2016

SPIE Proceedings

Self Cite

View full text Add to dashboard Cite

Several challenges hinder extreme ultraviolet lithography (EUVL) photomask fabrication and its readiness for high volume manufacturing (HVM). The lack in availability of pristine defect-free blanks as well as the absence of a robust mask repair technique mandates defect mitigation through pattern shift for the production of defect-free photomasks. The work presented here provides a comprehensive look at pattern shift implementation to intersect EUV HVM for the 7 nm technology node. An empirical error budget to compensate for measurement variability and errors, based on the latest HVM inspection and write tool capabilities, is first established and then experimentally verified. The validated error budget is applied to 20 representative EUV blanks and pattern shift is performed on fully functional 7 nm node chip designs. The probability of defect-free masks is explored for various layers, including metal, contact, and gate cut layers. From these results, an assessment is made on the current viability of defect-free EUV masks and what is required to construct a complete defect-free EUV mask set.

show abstract

Impact of EUV photomask line-edge roughness on wafer prints

Cited by 7 publications

References 1 publication

Ni-Al Alloys as Alternative EUV Mask Absorber

Ni-Al Alloys as Alternative EUV Mask Absorber

EUV lithography: LER design, mask, and wafer impact

Defect avoidance for EUV photomask readiness at the 7 nm node

Contact Info

Product

Resources

About