Following electroplating of Cu, residues of Cu are seen on the backside of the wafer. Bevel edge clean and backside clean seem to make it worse. Probably increases the roughness of the backside thus creating good adhesion for Cu from subsequent metal layers to stick to the backside. How else can this Cu residue be removed without increasing front side defectivity and lowering yield?
one way to clean would be to have an etching ( using cotton swabs) on the spots where copper appears in the back. The etchant would be a solution of ammonia and persulfate. Look for the composition in the literature
Although the wafer substrate material is not mentioned, you may probably consider cleaning the wafer from copper residue with aqueous solution of ammonium persulfate (about 40 wt %) slightly acidified with conc. sulphuric acid (about 2 drops / 100 ml).
The combination of ammonia and ammonium persulfate works best since it forms a copper ammonia complex and does not etch the base metal. .If the substrate is not attacked by ammoniacal solutions this solution will work well
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Plating