Jan 15 2014

Expert Advice: Removing Surface Contamination

Substances that are easily removed from the surface are organic, carbon containing deposits, polymers and the like.  These are removed with oxgyen plasmas.  Can also be removed with hydrogen plasmas.  This is the most common application.  Contamination is divided into two categories:  fine, <0.25 microns thick; gross >0.25 microns thick.  The fine contamination is always present underneath the gross contamination.  Sometimes gross contamination is there and sometimes it is not.
The plasma can strip away organic materials at several microns per second.  However, this occurs directly underneath the beam.  When the gross contamination is spread across the surface, and you have to sweep the beam over that surface, it can take a long time to remove this contamination, and may make the process too expensive.  If the gross contamination covers an area smaller then the beam spot, and it is only in a few areas on the substrate, then this would be a good application for atmospheric plasma.  A wet clean is recommended if gross contamination is spread over a large area.
The fine contamination is removed extremely fast, and the plasma is required for this.  A wet clean probably will not be a good alternative to plasma in this case.
An optimal strategy is wet clean for gross contamination, and atmospheric plasma for fine contamination.
Metal oxides can be removed from surfaces quickly with a hydrogen plasma, provided the metals are group VIII and IB transition metals: Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au.
Silicon can be removed slowly with a fluorine plasma.
Best regards,
Dr. Bob Hicks

Leave a Reply

Your email address will not be published.