Gaylor,
     
     Not sure where you are hearing that Plasma is good, but past fab shop 
     I've worked for or surveyed from the customer end, have moved away 
     from using plasma.  I could be wrong and someone in the forum may 
     correct me, but this has been the underlying trend.  
     
     Several reasons are:
     
     1. Cost, the dry-chemicals are very expensive.
     2. You typically have non-uniform smear removal of the hole wall.
     3. Check your local city and state ordinance on chemicals.
     4. Expensive equipment.
     5. Proper air ventilation in-place
     
     
     If you have low volumes, use sulfuric acid, but have safe and 
     preventive measures in place.
     
     For higher volumes, I would highly recommend using Permanganate for 
     smear removal.  The advantages outweigh the disadvantages of using 
     this make-up.  Once you have your two chemistries mixed, just add DI 
     or replace evaporated water.
     
     Regards,
     
     John Gulley - QA
     Inet Inc.
     Plano, TX  75075-7270
     


______________________________ Reply Separator _________________________________
Subject: Plasma
Author:  [log in to unmask] (Timothy Gaylor) at Internet
Date:    1/23/97 11:25 PM


I am interested in the Plasma desmear process. I have been reading alot 
about this type of desmear technique and dont quite understand the 
variables involved.
     
>From what I understand there is a combination of three gasses that 
combine to create the "plasma" state ( the most common oxygen, nitrogen 
and tetraflouromethane). 
     
How are these gasses controlled and what effects do the ratio of the 
gasses effect the etchrate?
     
T.A. Gaylor 
     
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