[Spm] Co2 Snow Cleaning

[Igor Sokolov]

Dear Vahid, 

It has recently been discussed with respect to the cleaning of AFM calibration grids. For curiosity reasons, I asked several people, who worked with this technique, about its capabilities. The below is what I found out. Apparently, this method has been used since mid 80's. It works well for removing organics (liquid CO2 is a great organic solvent) and microparticles (via a not completely understood process, presumably involving big thermal gradients, tribo-electricity, etc.). Removing nanoparticles is tricky, and depends on the nature of nanoparticle-surface interaction (how strong it is). There were several attempts to utilize CO2 show cleaning for post-CMP (chemical-mechanical planarization) process, in which one needs to remove attached residues and nanoparticles. It was not entirely successful. The culprit was in condensation of organics from the air and the electrostatic charges induced when cleaning an insulating surface. It means that an organic-free environment may be needed if the surface must be molecular clean. 
There is another sibling technology, argon gas to make cryogenic aerosols (was tried by IBM). This method removes nanoparticles much more effectively. However, this technique consumes large amount of argon, and has to be done at 0.5 atm pressure, which makes it not very convenient..

I would glad to learn others' experience because this method seems to be attractively simple..

Best regards,
Igor



_____________________________________
Igor Sokolov, Ph.D.
Professor,
Department of Physics,
Department of Chemistry and Biomolecular Science,
Director of Nanoengineering and Biotechnology Laboratories Center (NABLAB), 
NY Center for Advanced Material Processing (CAMP)
Clarkson University, 
Potsdam, NY 13699

Phone:     315-268-2375
Fax:       315-268-6610
email:     isokolov at clarkson.edu
Web:       http://www.clarkson.edu/~isokolov
           http://www.clarkson.edu/~nablab
_____________________________________

-----Original Message-----
From: vvahdat at seas.upenn.edu [mailto:vvahdat at seas.upenn.edu] 
Sent: Wednesday, October 07, 2009 2:33 PM
To: Spm at spmlist.di.com
Subject: [Spm] Co2 Snow Cleaning


Hi,
Does anyone have experience with CO2 snow cleaning? I'd like to know  
what was your experience in using it? Does it really work to clean  
everything? And what are the limitations?

Thanks
Vahid