Acoustic streaming effects in megasonic cleaning of EUV photomasks: a continuum model

Kapila, Vivek; Deymier, Pierre A.; Shende, Hrishikesh; Pandit, Viraj; Raghavan, Srini; Eschbach, Florence O.

doi:10.1117/12.633378

Cited by 16 publications

(9 citation statements)

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“…The particle-substrate system is therefore modeled using moment and force balance arguments that define translation and/or detachment of the particle from the substrate surface if the magnitudes of the hydrodynamic applied torque and forces exceed critical limit values (e.g. [2,4,84]). …”

Section: Rigid Body Motionmentioning

confidence: 99%

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Modeling of surface cleaning by cavitation bubble dynamics and collapse

Chahine

Kapahi

Choi

et al. 2016

Ultrasonics Sonochemistry

313

101

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Surface cleaning using cavitation bubble dynamics is investigated numerically through modeling of bubble dynamics, dirt particle motion, and fluid material interaction. Three fluid dynamics models; a potential flow model, a viscous model, and a compressible model, are used to describe the flow field generated by the bubble all showing the strong effects bubble explosive growth and collapse have on a dirt particle and on a layer of material to remove. Bubble deformation and reentrant jet formation are seen to be responsible for generating concentrated pressures, shear, and lift forces on the dirt particle and high impulsive loads on a layer of material to remove. Bubble explosive growth is also an important mechanism for removal of dirt particles, since strong suction forces in addition to shear are generated around the explosively growing bubble and can exert strong forces lifting the particles from the surface to clean and sucking them toward the bubble. To model material failure and removal, a finite element structure code is used and enables simulation of full fluid-structure interaction and investigation of the effects of various parameters. High impulsive pressures are generated during bubble collapse due to the impact of the bubble reentrant jet on the material surface and the subsequent collapse of the resulting toroidal bubble. Pits and material removal develop on the material surface when the impulsive pressure is large enough to result in high equivalent stresses exceeding the material yield stress or its ultimate strain. Cleaning depends on parameters such as the relative size between the bubble at its maximum volume and the particle size, the bubble standoff distance from the particle and from the material wall, and the excitation pressure field driving the bubble dynamics. These effects are discussed in this contribution.

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Section: Rigid Body Motionmentioning

confidence: 99%

“…Non-chemical submerged surface cleaning is accomplished through application of shear forces at the surface to be cleaned large enough to lift adhered particles [1][2][3][4]. This can be achieved by using liquid jets or high frequency acoustic waves (ultrasonic, megasonic).…”

Section: Introductionmentioning

confidence: 99%

Modeling of surface cleaning by cavitation bubble dynamics and collapse

Chahine

Kapahi

Choi

et al. 2016

Ultrasonics Sonochemistry

313

101

View full text Add to dashboard Cite

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“…However, during cavitation, stable cavities are also formed which can undergo large amplitude pulsations resulting into micro-streaming and such micro-streaming can lead to intense shear stresses along the boundary [6]. These shear stresses lead to drag forces and rolling moments which subsequently overcome the adhesion force between particle and surface [7]. Since there are no shock waves generated, the chances for Ru pitting reduce significantly (figure 3).…”

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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“…Acoustic streaming reduces the thickness of the hydrodynamic boundary layer on the surface of the substrate. Smaller size particles are then exposed to large velocity gradients that lead to drag force and rolling moments which subsequently overcome the adhesion force between particle and surface [13]. Acoustic cavitation is reported to address particles on the surface in various ways; 1) the implosion of cavitating bubbles increases the temperature and pressure which creates shock waves in the liquid; 2) due to asymmetric implosion of the cavitating bubbles, fluid jets can form; 3) some stable cavities can undergo large amplitude pulsations resulting in micro-streaming which can lead to intense shear stresses along the boundary [14].…”

Section: Megasonic Damage Investigationmentioning

confidence: 99%

Advanced cleaning of nano-imprint lithography template in patterned media applications

Singh¹,

Chen²,

Dress³

et al. 2010

SPIE Proceedings

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As the magnetic storage industry roadmap calls for aggressive terabit/in 2 densities over the next few years, the shift from the current planar media to patterned media; grooved surfaces (discrete track media / DTM) and/or individually defined magnetic dots (bit patterned media / BPM), will be necessary. Both types of patterned media require lithography to produce the pattern on the disk and the most promising lithography candidate today is nano-imprint lithography (NIL). During the imprinting process a thin, round, transparent template made of quartz is functioned as a mold to inversely transfer the features from its surface to the patterning medium on the disks by direct contact. One issue with this technique is the high probability of defects due to repeated contact of the template with the resist before, during, and after UV radiation. Defect management through template cleaning, inspection and defect characterization is critical to preserve integrity of the process. In this paper, advanced acid-free cleaning combined with MegaSonic treatment for defect elimination is investigated for effectiveness on discrete track recording (DTR) and BPM patterned templates. For the experiments, templates containing 250KTPI (100nm track pitch) full surface DTR pattern, 450 KTPI (56nm track pitch) with narrow band DTR pattern, and 250Gdpsi (50nm track pitch) with narrow band BPM pattern are used. The effect of MegaSonic cleaning on the pattern integrity of fragile features is studied. General characterization of defect attributes is made feasible through a series of imprinting and template cleaning cycles focused on resist residues and contaminant removal. Imprinted disks are analyzed using Candela disk inspection and SEM imaging of the pattern. Template cleaning is performed using HamaTech MaskTrack TeraPure automated template cleaning system.

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Acoustic streaming effects in megasonic cleaning of EUV photomasks: a continuum model

Cited by 16 publications

References 0 publications

Modeling of surface cleaning by cavitation bubble dynamics and collapse

Modeling of surface cleaning by cavitation bubble dynamics and collapse

Extending Ru capping layer durability under physical force cleaning

Advanced cleaning of nano-imprint lithography template in patterned media applications

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