The main difference between the two cleaning mechanisms is cavitation. In
ultrasonics (<100Khz), cavitation occurs at relatively low power, is
omni-directional, and is strong enough to cause damage, which is why they
are not typically used with Silicon.

Megasonics (800-1000Khz) create micro-cavitation which also releases very
high energy, but the bubble size is so much smaller that the chances of
damage are not as great. There are also several types of acoustic streaming
that occur in Megasonics which help reduce the boundary layer at the
substrate surface and enhance chemical cleaning.

If you are looking at Megasonics, expect to pay roughly 10x the cost of
Ultrasonics. They are much more difficult to build and the Electronics are
much more sophisticated. There are varying methods of coupling the sound
energy from the transducers and this makes a significant difference in
cleaning effectiveness.

I work for a company that manufactures Megasonic Systems. If you are
interested in discussing your application, feel free to send me an email
offboard.

Mark West
mwest@imtecacculine.com
-----Original Message-----
From: mems-talk-admin@memsnet.org [mailto:mems-talk-admin@memsnet.org]On
Behalf Of Piao, Fan
Sent: Tuesday, July 30, 2002 3:08 PM
To: 'mems-talk@memsnet.org'
Subject: [mems-talk] Ultrasonic Vs. Megasonic clean


Can someone help me understand the difference between ultrasonic and
megasonic
clean mechanisms? Why do we generally need to use megasonic clean in Si
process
instead of ultrasonic clean?
Thanks,

Fan Piao
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