Megasonic cleaning is a type of

acoustic cleaning Acoustic cleaning is a maintenance method used in material-handling and storage systems that handle bulk granular or particulate materials, such as grain elevators, to remove the buildup of material on surfaces. Acoustic cleaning apparatus, ...

, related to

ultrasonic cleaning Ultrasonic cleaning is a process that uses ultrasound (usually from 20 to 40 kHz) to agitate a fluid, with a cleaning effect. Ultrasonic cleaners come in a variety of sizes, from small desktop units with an internal volume of less than , to larg ...

. It is a gentler cleaning mechanism, less likely to cause damage, and is used in wafer, medical implant, and industrial part cleaning. Similar to ultrasonic cleaning, megasonics utilizes a

transducer A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation, measurement, and contr ...

that usually sits atop a

piezoelectric Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied Stress (mechanics), mechanical s ...

substrate. The transducer creates an acoustic field at a much higher

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

(typically 0.8–2 MHz) compared to ultrasonic cleaning (20-200 kHz). As a result, the

cavitation Cavitation is a phenomenon in which the static pressure of a liquid reduces to below the liquid's vapour pressure, leading to the formation of small vapor-filled cavities in the liquid. When subjected to higher pressure, these cavities, cal ...

that occurs is gentler and on a much smaller scale. Megasonics are currently used mainly in the electronics industry for preparation of silicon wafers. Barbara Kanegsberg, Edward Kanegsberg (ed), ''Handbook for Critical Cleaning: Cleaning Agents and Systems, Second Edition'',CRC Press, 2011, pp.245-247

Megasonics cleaning compared to ultrasonic cleaning

The difference between ultrasonic cleaning and megasonics cleaning lies in the frequency that is used to generate the acoustic waves. Ultrasonic cleaning uses lower frequencies, and produces random

. Megasonics cleaning uses higher frequencies, and produces controlled cavitation. An important distinction between the two methods is that the cavitation effects in a megasonic bath are much less damaging than those found with ultrasonic frequencies. This significantly reduces or eliminates cavitation erosion and the likelihood of surface damage to the product being cleaned. Parts that would be damaged by ultrasonic frequencies or cavitation effects can often be cleaned without damage in a megasonic bath using the same solution. With ultrasonics, cavitation occurs throughout the tank, and all sides of submerged parts are cleaned. With megasonics, 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 so that both front and back surfaces can be cleaned. Special carriers are sometimes used to reduce any obstructions that may prevent parts of the wafer surface from being cleaned. Today, for single wafer cleaning there are not only megasonic tanks and transducer plates, but also different configurations. For example, so called megasonic single- or dual- nozzle systems, or single-wafer transducers. In these configurations the single wafer is turning on a spinning tool and the megasonics is applied from above by the nozzle (liquid stream) or by the face-to-face transducer (partial area excited by megasound).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.

References

{{Reflist Ultrasound Cleaning methods

Megasonics cleaning compared to ultrasonic cleaning

See also

References