Study on surface integrity in photomask resist strip and final cleaning processes

Singh, Sherjang; Helbig, Stefan; Dress, Peter; Dietze, Uwe

doi:10.1117/12.824254

Cited by 14 publications

(9 citation statements)

References 15 publications

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“…Earlier SUSS MicroTec Photomask Equipment (former HamaTech APE) has published extensive research on the MegaSonic phenomenon where SRAF damage free cleaning is demonstrated [8][9][10][11][12][13]. In this study we applied the MegaSonic knowledge gained while solving SRAF damage issue in 193i mask, to resolve the Ru pitting issue on the EUV mask.…”

Section: Introductionmentioning

confidence: 93%

Extending Ru capping layer durability under physical force cleaning

Singh

Dietze

Dress

2013

Extreme Ultraviolet (EUV) Lithography IV

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Physical force wet cleaning technologies (MegaSonic & Droplet Spray) are considered the supreme challenge in 193i reticle cleaning due to smaller critical dimension, high feature aspect ratio, and sensitive interfaced fragile features. However this was not considered equally challenging in EUV masks. Recently, MegaSonic cavitation has been linked to Ru (capping layer) pitting issues; making the use of acoustic based cleaning questionable for EUVL reticles. Nevertheless, acoustic energy is necessary to remove particles trapped in deep and congested trenches. This strengthens the need to control the physical force energy within the damage free regime even further. In this study we have investigated method to control MegaSonic cavitation as well as established a link between pattern damage observed in optical mask and Ru pitting in EUV masks. Effect of different cleaning chemistries typically used in mask cleaning is compared with a new cleaning chemistry (referred to as chemical A). A new POR (Process of Record) based on chemical A is qualified and its effects on PRE, absorber CD and EUV-reflectivity are discussed.

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Section: Introductionmentioning

confidence: 93%

Extending Ru capping layer durability under physical force cleaning

Singh

Dietze

Dress

2013

Extreme Ultraviolet (EUV) Lithography IV

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“…When such hydroxyl radicals are exposed to cured imprint resist materials or other organic compounds (C-H) they react primarily by hydrogen abstraction (deprotonation) to produce an organic radical (R`) (4), which reacts quickly with dissolved oxygen to yield an intermediate organic peroxyl (RO2') (5). These intermediates initiate thermal (chain) reactions of oxidative degradation, leading finally to carbon dioxide, water, and inorganic salts [9].…”

Section: Imprint Materials Removalmentioning

confidence: 99%

“…As with the semiconductor device NIL templates, the Silica wafers utilize similarly patterned "mesa" areas. Some of the most advanced cleaning processes have been developed to meet stringent mask integrity requirements of current and future EUVL and 193i lithography [5][6][7]. Developed on optical 4:1 reticles with different material composition, these advanced cleaning processes are not directly transferrable to a NIL template cleaning process.…”

Section: Introductionmentioning

confidence: 99%

Effects of cleaning on NIL templates: surface roughness, CD, and pattern integrity

et al. 2011

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Nano-Imprint Lithography (NIL) is considered a promising alternative to optical lithography for technology nodes at 22nm hp and beyond. Compared to other advanced and complex lithography methods, NIL processing is simple and inexpensive making it a widely accepted technology for pattern media and a potential cost effective alternative for CMOS applications. During the NIL process, the template comes into direct contact with the resist on the substrate and consequently template cleanliness plays a decisive role in imprinted substrate quality. Furthermore, if the template has any form of a defect such as resist residue, stains, particles, surface scratches, chipping and bumping etc. it can lead to poor quality imprints, low yield and throughput decreases. The latest ITRS roadmap has stringent CD, CD uniformity, surface roughness and defect control requirements for NIL templates. Any template cleaning process that is adopted must be able to remove defects while maintaining the critical parameters outlined by the ITRS. Aggressive chemistries (such as NH 4 OH or SC1 (NH 4 OH+H 2 O 2 +DI) and strong physical force treatments (such as MegaSonic & Binary Sprays) may cause damage to the template if not optimized. This paper presents the cleaning chemical effects on template surface roughness and CD at varying concentrations. The effect of physical force cleaning on fragile and sensitive pattern features is also presented. Particle & imprint resist removal efficacy at different process conditions is compared.

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“…Earlier [23,24], HamaTech APE demonstrated an advanced, non-acid method to preserve surface integrity of EUV blanks. This method was based on UV photolysis of liquid media at point-of-use and is a key component of the processof-record (POR) used in this experiment.…”

Section: Experiments Conditions and Detailsmentioning

confidence: 99%

Effective EUVL mask cleaning technology solutions for mask manufacturing and in-fab mask maintenance

Dietze¹,

Dress²,

Waehler³

et al. 2011

27th European Mask and Lithography Conference

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Extreme Ultraviolet Lithography (EUVL) is considered the leading lithography technology choice for semiconductor devices at 16nm HP node and beyond. However, before EUV Lithography can enter into High Volume Manufacturing (HVM) of advanced semiconductor devices, the ability to guarantee mask integrity at point-of-exposure must be established. Highly efficient, damage free mask cleaning plays a critical role during the mask manufacturing cycle and throughout the life of the mask, where the absence of a pellicle to protect the EUV mask increases the risk of contamination during storage, handling and use. In this paper, we will present effective EUVL mask cleaning technology solutions for mask manufacturing and in-fab mask maintenance, which employs an intelligent, holistic approach to maximize Mean Time Between Cleans (MBTC) and extend the useful life span of the reticle. The data presented will demonstrate the protection of the capping and absorber layers, preservation of pattern integrity as well as optical and mechanical properties to avoid unpredictable CD-linewidth and overlay shifts. Experiments were performed on EUV blanks and pattern masks using various process conditions. Conditions showing high particle removal efficiency (PRE) and minimum surface layer impact were then selected for durability studies. Surface layer impact was evaluated over multiple cleaning cycles by means of UV reflectivity metrology XPS analysis and wafer prints. Experimental results were compared to computational models. Mask life time predictions where made using the same computational models. The paper will provide a generic overview of the cleaning sequence which yielded best results, but will also provide recommendations for an efficient in-fab mask maintenance scheme, addressing handling, storage, cleaning and inspection.

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Study on surface integrity in photomask resist strip and final cleaning processes

Cited by 14 publications

References 15 publications

Extending Ru capping layer durability under physical force cleaning

Extending Ru capping layer durability under physical force cleaning

Effects of cleaning on NIL templates: surface roughness, CD, and pattern integrity

Effective EUVL mask cleaning technology solutions for mask manufacturing and in-fab mask maintenance

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