Megasonic cleaning: possible solutions for 22nm node and beyond

Shende, Hrishi; Singh, Sherjang; Baugh, James; Mann, Raunak; Dietze, Uwe; Dress, Peter

doi:10.1117/12.898409

Cited by 7 publications

(7 citation statements)

References 5 publications

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“…SC1 and Chemistry A show similar level of acoustic energy transfer ( figure 9). It has been well known that a photomask cleaning process using H 2 -DI, if used at proper gas concentration, shows lesser pattern damage than the equivalent cleaning process with SC1 [11,12]; therefore figure 10 only shows the comparison of pattern damage performance between H 2 -DI based and Chemistry A based mask cleaning processes. SC1 data was not collected intentionally.…”

Section: Acoustic Energy and Pattern Damagementioning

confidence: 98%

Effect of cleaning chemistry on MegaSonic damage

Singh¹,

Dietze²,

Dress

2013

SPIE Proceedings

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Acoustic energy applied through the cleaning media results into two kinds of cavitation effects; namely stable and transient cavitation. A uniformly pulsating bubble transforms into stable cavitation behavior whereas a bubble implosion implies transient cavitation. Pattern damage of sensitive features on advanced masks as well as Ru pitting on EUVL reticles is mostly the result of transient cavitation. Stable cavitation on the other hand produces a very narrowly controlled energy distribution which allows cleaning without damage. Stable cavitation can be achieved by suitably tailoring physical, chemical and thermodynamic properties of the liquid and gas media. In this paper we investigate a new cleaning chemistry that has favorable physical and thermodynamic properties to produce stable MegaSonic cavitation. The cavitation created in this chemistry is characterized by measuring acoustic energy as well as by pattern damage and particle removal efficiency on mask level. The chemical properties (pH & zeta potential) of this chemistry are compared with conventional cleaning chemistries. Its effects on CD shift as well as phase and transmission loss are also studied.

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Section: Acoustic Energy and Pattern Damagementioning

confidence: 98%

Effect of cleaning chemistry on MegaSonic damage

Singh¹,

Dietze²,

Dress

2013

SPIE Proceedings

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“…Several criteria can influence cavitation behavior, including system temperature, particle size, particle composition, and the acoustic stimulation frequency. − The focus of this study is the comparative effects of two stimulation frequencies: 20 kHz (ultrasonic) and 1 MHz (megasonic). Ultrasonically enhanced dissolution of minerals has focused on stimulation at low ultrasonic frequencies (i.e., 16–40 kHz). ,,,− In contrast, megasonic stimulation (i.e., greater than 1 MHz) is used for fine tasks such as the cleaning of delicate equipment (e.g., microchips, − flat panel displays, , photomasks, , etc.). These varied stimulation frequencies give rise to different critical cavitation bubble sizes, with values of ∼150 μm at 20 kHz and of ∼4 μm at 1 MHz .…”

Section: Introductionmentioning

confidence: 99%

“…Ultrasonically enhanced dissolution of minerals has focused on stimulation at low ultrasonic frequencies (i.e., 16−40 kHz). 1,2,4,20−22 In contrast, megasonic stimulation (i. greater than 1 MHz) is used for fine tasks such as the cleaning of delicate equipment (e.g., microchips, 23−27 flat panel displays, 28,29 photomasks, 30,31 etc.). These varied stimulation frequencies give rise to different critical cavitation bubble sizes, with values of ∼150 μm at 20 kHz and of ∼4 μm at 1 MHz.…”

Section: ■ Introductionmentioning

confidence: 99%

Dissolution Amplification by Resonance and Cavitational Stimulation at Ultrasonic and Megasonic Frequencies

et al. 2022

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Acoustic stimulation offers a green pathway for the extraction of valuable elements such as Si, Ca, and Mg via solubilization of minerals and industrial waste materials. Prior studies have focused on the use of ultrasonic frequencies (20–40 kHz) to stimulate dissolution, but megasonic frequencies (≥1 MHz) offer benefits such as matching of the resonance frequencies of solute particles and an increased frequency of cavitation events. Here, based on dissolution tests of a series of minerals, it is found that dissolution under resonance conditions produced dissolution enhancements between 4×-to-6× in Si-rich materials (obsidian, albite, and quartz). Cavitational collapse induced by ultrasonic stimulation was more effective for Ca- and Mg-rich carbonate precursors (calcite and dolomite), exhibiting a significant increase in the dissolution rate as the particle size was reduced (i.e. available surface area was increased), resulting in up to a 70× increase in the dissolution rate of calcite when compared to unstimulated dissolution for particles with d 50 < 100 μm. Cavitational collapse induced by megasonic stimulation caused a greater dissolution enhancement than ultrasonic stimulation (1.5× vs 1.3×) for amorphous class F fly ash, despite its higher Si content because the hollow particle structure was susceptible to breakage by the rapid and high number of lower-energy megasonic cavitation events. These results are consistent with the cavitational collapse energy following a normal distribution of energy release, with more cavitation events possessing sufficient energy to break Ca–O and Mg–O bonds than Si–O bonds, the latter of which has a bond energy approximately double the others. The effectiveness of ultrasonic dissolution enhancement increased exponentially with decreasing stacking fault energy (i.e., resistance to the creation of surface faults such as pits and dislocations), while, in turn, the effectiveness of megasonic dissolution increased linearly with the stacking fault energy. These results give new insights into the use of acoustic frequency selections for accelerating elemental release from solutes by the use of acoustic perturbation.

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“…Although, both stable and transient cavitation aid in the removal of particles through microstreaming and shock waves/microjet formation respectively, the disadvantage of exploiting transient cavitation for cleaning is that it causes significant damage to thin and fragile features. Over the years, megasonic cleaning processes in semiconductor industry have constantly evolved through investigations of various parameters such as cleaning chemistries, dissolved gases, 3 sound field frequency, 4 transducer power density, particulate contaminant size and aspect ratio of trenches 5,6 on particle removal efficiency.…”

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confidence: 99%

A Sono-Electrochemical Technique for Enhanced Particle Removal from Tantalum Surfaces

Balachandran

Deymier

Raghavan

et al. 2014

ECS Solid State Letters

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Low power megasonics is of interest to semiconductor cleaning community due to minimal feature damage. In this work, megasonic field at low power density in conjunction with electrochemistry is used for enhanced removal of silica particles from tantalum wafers. Cleaning studies were conducted in air or argon saturated aqueous solutions at 0.5 W/cm 2 in the absence and presence of applied potentials of −1.5 V or −2.0 V to tantalum (vs Ag/AgCl). The improvement in particle removal efficiency is attributed to oscillating hydrogen bubbles formed from water reduction in vicinity of tantalum surface and grown to a resonant size under suitable acoustic conditions.

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Megasonic cleaning: possible solutions for 22nm node and beyond

Cited by 7 publications

References 5 publications

Effect of cleaning chemistry on MegaSonic damage

Effect of cleaning chemistry on MegaSonic damage

Dissolution Amplification by Resonance and Cavitational Stimulation at Ultrasonic and Megasonic Frequencies

A Sono-Electrochemical Technique for Enhanced Particle Removal from Tantalum Surfaces

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