Summary for copper oxide removal Discussion
Copper oxide removal before plating is the key issue in this thread. Sarah Smith asked whether a copper seed layer on wafers really needs a water rinse and sulfuric acid dip before electroplating, since many sources mention only deionized water and the bath itself is acidic. In reply, the answerer said adhesion depends on bonding to the substrate, and if copper oxide remains, the deposit will bond to the oxide rather than directly to copper, making the coating much weaker. The practical conclusion was clear: yes, copper oxide should be removed to get a good bond before electrodeposition. The answerer emphasized the general plating rule that cleanliness is critical, especially when adhesion matters.
Q. I’m just looking for some information on pre-treatment of wafers before they get electroplated with copper.
The process I am working on involves plating copper onto a copper seed layer. The pre-treatment involves immersion in water followed by immersion in sulfuric acid. The thinking is that this is needed to remove copper oxide. However from reading this website and lots of others I can’t see this ever being raised as an issue. Lots of sites mention dipping wafers in deionized water but no other “cleaning” step before plating. So is it possible to plate onto copper oxide, or is pre cleaning really an issue as the plating bath is acidic anyway? Really appreciate any help
Sarah Smith
– Sydney, Australia
April 25, 2012
A. Sarah, When electrodepositing onto a substrate, adhesion is achieved by the bonding of the coating material to the substrate. Copper oxide is a thin layer on top of copper, so your deposit will be adhering to the copper oxide and will be much weaker than if it was attached directly to the copper. I was always taught that “cleanliness is next to Godliness” – since I have worked in the electroplating industry I have learnt that “cleanliness IS Godliness”. Yes, you do need to remove the copper oxide to get a good bond.
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
May 1, 2012