Megasonic cleaning
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Megasonic cleaning is a type of acoustic cleaning related to ultrasonic cleaning. It is a gentler cleaning mechanism that is less likely to cause damage.[1] Megasonics are currently used mainly in the electronics industry in various semiconductor device fabrication processes.[2]
Similar to ultrasonic cleaning, a megasonic cleaner utilizes a transducer that usually sits on top of a piezoelectric substrate. The transducer creates an acoustic field at a much higher frequency (typically 0.8–2 MHz) compared to ultrasonic cleaning (20-200 kHz). As a result, the cavitation that occurs is gentler and on a much smaller scale.
Comparison to ultrasonic cleaning
Megasonic cleaning differs from ultrasonic cleaning in the frequency that is used to generate the acoustic waves. Ultrasonic cleaning uses lower frequencies and produces random cavitation. Megasonic cleaning uses higher frequencies and produces controlled cavitation. As a result, damage caused by cavitation is minimized in megasonic baths.
In ultrasonic devices, cavitation occurs throughout the tank, and all sides of submerged parts are cleaned. In megasonic devices, the acoustic wave is found only in a line of sight from the transducer surface. For this reason, megasonic transducers are typically built using arrays of square or rectangular piezo devices bonded to a substrate, and spaced as close together as possible. Semiconductor wafers are typically cleaned in carriers holding the substrates perpendicular to the transducer, allowing both the front and back surfaces to be cleaned. Special carriers are sometimes used to reduce any obstructions that may prevent parts of the wafer surface from being cleaned.[2]
Megasonic cleaners come in many configurations, such as single-nozzle or dual-nozzle systems, or single-wafer transducers. In single-wafer devices, the wafer rotates on a spinning tool and the megasonic waves are applied from above by the nozzle (liquid stream) or by the face-to-face transducer (partial area excited by megasound).[3]
See also
References
- ^ Nagarajan, R.; Awad, S.; Gopi, K. R. (2011-01-01), Kohli, Rajiv; Mittal, K. L. (eds.), "Chapter 2 - Megasonic Cleaning", Developments in Surface Contamination and Cleaning, Oxford: William Andrew Publishing, pp. 31–62, ISBN 978-1-4377-7885-4, retrieved 2023-10-15
- ^ a b Barbara Kanegsberg, Edward Kanegsberg (ed), Handbook for Critical Cleaning: Cleaning Agents and Systems, Second Edition,CRC Press, 2011, ISBN 1439828288 pp.245-247
- ^ Holsteyns, F. et al (2008). Ex Situ Bubble Generation, Enhancing the Particle Removal Rate for Single Wafer Megasonic Cleaning Processes. Solid State Phenomena. 134. 201-204. 10.4028/www.scientific.net/SSP.134.201.