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Chapter 2
R. Nagarajan, S. Awad and K.R. Gopi
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FIGURE 2.1 Finite element simulation of propagation of megasonic waves in a tank [12]
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FIGURE 2.2 Micro-streaming in a megasonic field [15]
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FIGURE 2.3 Cross-sectional diagrams of (a) ultrasonic and (b) megasonic cleaners [18]
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FIGURE 2.4 Ultrasonic cavitations and cleaning
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FIGURE 2.5 Growth and collapse (implosion) of a cavitation bubble
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FIGURE 2.6 Cavitation strength as a function of frequency
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FIGURE 2.7 Cavitation abundance varies with frequency
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FIGURE 2.8 Change in boundary layer thickness (relative to contaminant size) from ultrasonic to megasonic regime
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FIGURE 2.9 The relationship between frequency and boundary layer thickness for room temperature water (theoretical simulation)
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FIGURE 2.10 Effect of acoustic field parameters on streaming velocity [23]
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FIGURE 2.11 Moment ratio model for particle removal from a surface. MR is the removal moment; MA is the adhesion resisting moment; Fdrag is the drag force; FAdhesion is the adhesion force; Felec double layer is the electric double layer force; R is the particle radius; a is the contact radius between the deformed particle and the surface [23]
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FIGURE 2.12 Experimental and theoretical particle removal efficiencies. Si-cap refers to a 4 nm silicon capping layer on the wafer [23]
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FIGURE 2.13 Fluid motion generated by a sound field [24]
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FIGURE 2.14 Removal and adhesion forces on a spherical particle [25]
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FIGURE 2.15 Variation of streaming velocity with frequency
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FIGURE 2.16 Optical principle of the liquid particle counter
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FIGURE 2.17 Schematic diagram of a nephelometer
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FIGURE 2.18 Cavitation meter
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FIGURE 2.19 Cavitation intensity as a function of frequency and position within the cleaning tank
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FIGURE 2.20 Mean cavitation intensity as a function of frequency ( kHz)
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FIGURE 2.21 Influence of dissolved oxygen on the particle removal efficiency (PRE) of 34-nm SiO2 particles [30]
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FIGURE 2.22 Particle removal efficiency for 78- and 34-nm SiO2 particles in aerated deionized (DI) water and ammonia/peroxide mixture (APM) solutions (a) with megasonic agitation and (b) without megasonic agitation [37]
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FIGURE 2.23 Traditional non-sweeping megasonic power distribution in a cleaning vessel
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FIGURE 2.24 Sweep megasonic power distribution in a cleaning vessel
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FIGURE kHz tank with sweeping (courtesy of Crest Ultrasonics Corporation, USA)
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FIGURE 2.26 Cavitation intensities in center and corners of sweeping megasonics (470 kHz from MSI, Inc., USA) and traditional megasonics (430 kHz)
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FIGURE 2.27 Erodibility comparison at center of tank (based on turbidity measurement on extract solution)
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FIGURE 2.28 Cleanability comparison at the center of the tank based on turbidity measurement of the extract solution
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FIGURE 2.29 Mean size of surface residual particles after multiple cleaning stages
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FIGURE 2.30 Comparison of cleaning efficiency of swept (470 kHz) and traditional (430 kHz) megasonic cleaning
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FIGURE 2.31 Defect number after various cleaning processes [36]
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FIGURE 2.32 Particle residue by type after various cleaning processes [36]
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