Megasonic cleaning of wafers in electrolyte solutions: Possible role of electro-acoustic and cavitation effects

Keswani, Manish; Raghavan, Srini; Deymier, Pierre A.; Verhaverbeke, Steven

doi:10.1016/j.mee.2008.09.042

Cited by 41 publications

(19 citation statements)

References 17 publications

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“…Still, pressures may be of the order of 10 3 -10 4 bars. The range of driving pressures analysed here is the typical operating range of megasonic cleaning devices (Kapila et al 2006;Holsteyns et al 2008;Minsier & Proost 2008;Ahn et al 2009;Keswani et al 2009). An uncontrolled radiation by cavitation bubble fields will result in mechanical failure, when the high peak energies of the radiated sound containing highfrequency components drive unwanted mechanical oscillations.…”

Section: Discussionmentioning

confidence: 99%

Acoustic energy radiated by nonlinear spherical oscillations of strongly driven bubbles

Holzfuss

2010

Proc. R. Soc. A.

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Based on the theory of F. Gilmore (Gilmore 1952 The growth or collapse of a spherical bubble in a viscous compressible liquid) for radial oscillations of a bubble in a compressible medium, the sound emission of bubbles in water driven by high-amplitude ultrasound is calculated. The model is augmented to include expressions for a variable polytropic exponent, hardcore and water vapour. Radiated acoustic energies are calculated within a quasi-acoustic approximation and also a shock wave model. Isoenergy lines are shown for driving frequencies of 23.5 kHz and 1 MHz. Together with calculations of stability against surface wave oscillations leading to fragmentation, the physically relevant parameter space for the bubble radii is found. Its upper limit is around 6 mm for the lower frequency driving and 1-3 mm for the higher. The radiated acoustic energy of a single bubble driven in the kilohertz range is calculated to be of the order of 100 nJ per driving period; a bubble driven in the megahertz range reaches two orders of magnitude less. The results for the first have applications in sonoluminescence research. Megahertz frequencies are widely used in wafer cleaning, where radiated sound may be implicated as responsible for the damage of nanometre-sized structures.

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Section: Discussionmentioning

confidence: 99%

Acoustic energy radiated by nonlinear spherical oscillations of strongly driven bubbles

Holzfuss

2010

Proc. R. Soc. A.

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“…Understanding the driving mechanisms of acoustic streaming patterns within acoustofluidic devices is important in order to precisely control it for the enhancement or suppression of acoustic streaming for applications such as particle/cell manipulation [1-8], heat transfer enhancement [9][10][11][12], noncontact surface cleaning [13][14][15][16][17], microfluidic mixing [18][19][20][21][22][23][24][25][26][27], and transport enhancement [28][29][30][31][32][33][34][35].…”

Section: Introductionmentioning

confidence: 99%

“…INTRODUCTION Acoustic streaming is steady fluid motion driven by the absorption of acoustic energy due to the interaction of acoustic waves with the fluid medium or its solid boundaries. Understanding the driving mechanisms of acoustic streaming patterns within acoustofluidic devices is important in order to precisely control it for the enhancement or suppression of acoustic streaming for applications such as particle/cell manipulation [1-8], heat transfer enhancement [9-12], noncontact surface cleaning [13][14][15][16][17], microfluidic mixing [18][19][20][21][22][23][24][25][26][27], and transport enhancement [28][29][30][31][32][33][34][35].In most bulk micro-acoustofluidic particle and cell manipulation systems of interest, the acoustic streaming fields are dominated by boundary-driven streaming [36], which is associated with acoustic dissipation in the viscous boundary layer [37]. Theoretical work on boundary-driven streaming was initiated by Rayleigh [38], and developed by a series of modifications for particular cases [39][40][41][42][43][44], which have paved the fundamental understanding of acoustic streaming flows.…”

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confidence: 99%

Transducer-Plane Streaming Patterns in Thin-Layer Acoustofluidic Devices

2017

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While classical Rayleigh streaming, whose circulations are perpendicular to the transducer radiating surfaces, is wellknown, transducer-plane streaming patterns, in which vortices circulate parallel to the surface driving the streaming, have been less widely discussed. Previously, a four-quadrant transducer-plane streaming pattern has been seen experimentally and subsequently investigated through numerical modelling. In this paper, we show that by considering higher order threedimensional cavity modes of rectangular channels in thin-layered acoustofluidic manipulation devices, a wider family of transducer-plane streaming patterns are found. As an example, we present a transducer-plane streaming pattern, which consists of eight streaming vortices with each occupying one octant of the plane parallel to the transducer radiating surfaces, which we call here eight-octant transducer-plane streaming. An idealised modal model is also presented to highlight and explore the conditions required to produce rotational patterns. It is found that both standing and travelling wave components are typically necessary for the formation of transducer-plane streaming patterns. In addition, other streaming patterns related to acoustic vortices and systems in which travelling waves dominate are explored with implications for potential applications. DOI:I. INTRODUCTION Acoustic streaming is steady fluid motion driven by the absorption of acoustic energy due to the interaction of acoustic waves with the fluid medium or its solid boundaries. Understanding the driving mechanisms of acoustic streaming patterns within acoustofluidic devices is important in order to precisely control it for the enhancement or suppression of acoustic streaming for applications such as particle/cell manipulation [1-8], heat transfer enhancement [9-12], noncontact surface cleaning [13][14][15][16][17], microfluidic mixing [18][19][20][21][22][23][24][25][26][27], and transport enhancement [28][29][30][31][32][33][34][35].In most bulk micro-acoustofluidic particle and cell manipulation systems of interest, the acoustic streaming fields are dominated by boundary-driven streaming [36], which is associated with acoustic dissipation in the viscous boundary layer [37]. Theoretical work on boundary-driven streaming was initiated by Rayleigh [38], and developed by a series of modifications for particular cases [39][40][41][42][43][44], which have paved the fundamental understanding of acoustic streaming flows.While Rayleigh streaming patterns (which have streaming vortices with components perpendicular to the driving boundaries) have been extensively studied [45][46][47][48], we have recently explored the mechanisms behind fourquadrant transducer-plane streaming [49] which generates streaming vortices in planes parallel to the driving boundary, and modal Rayleigh-like streaming [50] in which vortices have a roll size greater than the quarter wavelength of the main acoustic resonance and are driven by limiting velocities (the value of the streaming velocity just outside...

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“…Sonochemical cleaning has proved to be particular effective, e.g., after preoxidation, pre-chemical vapor deposition, pre-epitaxial growth, postash and post-chemical mechanical polishing of Si wafers. It is commonly believed that the cleaning removes contaminating additives from the wafer surface through acoustic cavitation and acoustic streaming although the physics behind the ultrasonic-induced cleaning process is still not completely understood and the precise cleaning mechanisms are still the subject of debate [3,4]. The frequency range of the waves used in this process is rather wide, typically in the kHz-MHz range.…”

Section: Introductionmentioning

confidence: 99%

Water‐based sonochemical cleaning in the manufacturing of high‐efficiency photovoltaic silicon wafers

Nadtochiy

Podolian

Korotchenkov

et al. 2011

Phys. Status Solidi C

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We found that organic particle contaminants are effectively removed during ultrasonic cleaning in distilled water, as evidenced by the disappearance of organic‐related absorption peaks and remarkable shortening of the surface photovoltage decay transients (SPV). SPV decay transient mappings obtained with a 100‐μm spatial resolution (see abstract figure) show that, in multicrystalline Si wafers, the resulting effect on the decay time is markedly non‐uniform compared with that observed in crystalline Si, implying the existence of a mechanism associated with the grain boundaries. The data are tentatively interpreted in terms of the wafer hydrogenization, which most probably occur through the grain boundaries. It is assumed that elevated temperatures inside a cavitating bubble may lead to water and bubble gas decomposition, accompanied by a subsequent trapping of the decomposed particulates at the silicon surface. These particulates can then be predominantly incorporated into the grain boundary regions. We suggest that this can be in part due to hydrogen molecules decomposed in water which are mobile in silicon (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Megasonic cleaning of wafers in electrolyte solutions: Possible role of electro-acoustic and cavitation effects

Cited by 41 publications

References 17 publications

Acoustic energy radiated by nonlinear spherical oscillations of strongly driven bubbles

Acoustic energy radiated by nonlinear spherical oscillations of strongly driven bubbles

Transducer-Plane Streaming Patterns in Thin-Layer Acoustofluidic Devices

Water‐based sonochemical cleaning in the manufacturing of high‐efficiency photovoltaic silicon wafers

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