Cleaning Challenges of EUV Mask Substrates, Blanks, and Patterned Mask

Rastegar, Abbas; House, Matthew; Kadaksham, Arun John

doi:10.1149/1.3630837

Cited by 8 publications

(3 citation statements)

References 7 publications

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“…Cleaning methods for EUV photomasks can be classified into three categories: physical cleaning, which employs megasonic waves in conjunction with a standard clean-1 (SC-1) solution; wet cleaning, which uses solutions such as sulfuric acid-hydrogen peroxide mixture (SPM) or SC-1; and dry cleaning, which utilizes O 2 plasma ashing or UV/ Ozone exposure. Rastegar et al reported that physical cleaning with megasonic waves operates via two primary mechanisms: microstreaming and megasonic cavitation collapse, with the latter inflicting physical damage on the photomask surface [14]. Belau et al found that both the reflectivity and durability of EUV photomasks degrade due to etching and oxidation during dry cleaning processes [15].…”

Section: Introductionmentioning

confidence: 99%

Wet cleaning of Ta-based extreme ultraviolet photomasks at room temperature

Park,

Choi,

Kim

2024

Nanotechnology

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Owing to the wavelength-dependent limits of the deep ultraviolet (DUV) exposure process, the semiconductor industry introduced extreme ultraviolet (EUV) lithography operating at a 13.5-nm wavelength. Traditional photomasks employ pellicles for protection; however, EUV-specific pellicles are not widely applicable to commercial processes, requiring the development of a EUV photomask cleaning method. In this study, a wet cleaning method for Ta-based EUV photomasks at room temperature was systematically examined in terms of key parameters, including the pattern step height, surface topography, and particulate count, via atomic force microscopy and X-ray reflectivity. Post sulfuric acid-hydrogen peroxide mixture (SPM) treatment, the photomask exhibited a stable step height, indicating minimal pattern degradation. Additionally, discernible alterations in the surface roughness and a decrease in particle count were observed, further indicating to the effectiveness of SPM-mediated cleaning. Conversely, following SC-1 treatment, while the pattern step height remained relatively unchanged, a notable increase in surface irregularities and macroscopic particulates was observed, suggesting a suboptimal cleaning efficiency of the SC-1 solution despite its potential for pattern structure preservation. Our room temperature wet cleaning method efficiently reduces wear-out and successfully eliminates contaminants, potentially prolonging the EUV photomask's productivity and durability.

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Section: Introductionmentioning

confidence: 99%

Wet cleaning of Ta-based extreme ultraviolet photomasks at room temperature

Park,

Choi,

Kim

2024

Nanotechnology

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“…As mentioned at Introduction, there appear very various material surfaces to be cleaned at the same time in front and backend processes of EUV semiconductor technology such as metals, compounds, and low and high k dielectrics of various chemical forms of hydrides, hydrates, oxides, nitrides, carbides and so on. 21,22 Therefore, the wet cleaning requirements now become more stringent in view of EUV cleaning and rinsing concepts as well as of oxide formation before the following process step of nano-scale device fabrication. It has already been proven that cathode water showed the excellent performance for commercial application to clean the contaminated Sn on EUV mask.…”

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confidence: 99%

Evaluation of Anode Water Electrolyzed with Anion Exchange Membrane for Cleaning EUV Semiconductor

Kim,

Lim,

Ryoo

et al. 2023

ECS Adv.

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Electrically nonconducting UPW was electrolyzed without electrolyte through anion exchange membrane for evaluating applicability to EUV semiconductor cleaning. Produced anode water held positive ORP up to 900 mV, which is very oxidative. ORP, pH, and conductivity measurements showed delicately complementary each other for understanding anode water. Correlation of concurrent ORP decrease and conductivity increase in ultra-pure anode water domain was observed first time. The oxidative OH° was formed as the major species in anode water, causing positive ORP during ORP measurement. H+ and OH− ions, and OH° radical coexisted in anode water at amphoteric nonequilibrium, while pH was less than 6. It was concluded that OH°, as a strong oxidant, transformed itself to OH− by ORP measurement. OH° radical would oxidize selectively and then remove nano-contaminants. Anode water is considered to fulfill the requirement of EUV semiconductor cleaning where no oxygen species should be required because of likely oxide layer formation during cleaning, and it will even remove the native oxide developed unintentionally before cleaning.

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“…9 This damage creation is also a major bottleneck for EUV mask cleaning processes. 10 In this paper, a discussion of the fea-sibility of physical cleaning is given. Next, an overview of megasonic cleaning is presented, followed by a future outlook.…”

mentioning

confidence: 99%

Nanoparticle Removal with Megasonics: A Review

Brems

Hauptmann

Camerotto

et al. 2013

ECS J. Solid State Sci. Technol.

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Nanoparticle removal obtained without inflicting damage to fragile device elements remains a big challenge. The feasibility of physical cleans is assessed and boundary conditions are outlined. An overview of megasonic cleaning process improvements is given. In order to reduce damage without reducing particle removal frequencies during high frequency ultrasound cleaning processes, cavitation needs to be better controlled. This is partly achieved by (1) using pulsed acoustic fields which makes it possible to control the average bubble size and, at the same time, maximize the number of resonant bubbles, by (2) increasing the dissolved gas concentration and lowering the surface tension which facilitates bubble formation and, finally, by (3) introducing traveling waves to transport bubbles to the surface which needs to be cleaned.

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Cleaning Challenges of EUV Mask Substrates, Blanks, and Patterned Mask

Cited by 8 publications

References 7 publications

Wet cleaning of Ta-based extreme ultraviolet photomasks at room temperature

Wet cleaning of Ta-based extreme ultraviolet photomasks at room temperature

Evaluation of Anode Water Electrolyzed with Anion Exchange Membrane for Cleaning EUV Semiconductor

Nanoparticle Removal with Megasonics: A Review

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