Plasma etching of magnetic multilayers — effect of concurrent UV illumination

The etch products of magnetic materials such as NiFe and NiFeCo are not volatile in conventional plasma etching processes, but can be removed from the surface by ion-assisted desorption under high density plasma conditions. We have found that NiFeCo, CrSi and TaN, components of multilayer structures for magnetic random access memories, display enhanced etch rates in Cl2/Ar Inductively Coupled Plasmas with concurrent UV illumination during etching. No enhancement was observed when CO/NH3 plasma chemistries were employed. The enhanced etch rates correlate well with the presence of fewer chlorinated residues remaining on the surface, indicating more efficient desorption of the metal chloride etch products.