Electro-grafting: a new approach for copper seeding or direct plating

Among the critical processes to be developed for the next technological nodes, copper seed layer deposition is one of the least considered. We propose here to use electro-grafting to deposit ultra-thin, highly conformal, uniform and adherent seed layers. In this work, we evaluated two families of precursors that can be electro-grafted: 4-vinylpyridine (4VP), and diazonium (BDZ) derivatives. For both precursors, uniform organic films are deposited by electrochemical means. Efficient metal seeding is achieved in both cases. In the case of 4VP, direct co-deposition of copper during electro-grafting was used. Uniform and highly conformal 20 nm thick copper films were obtained. These seed layers were successfully used to initiate copper ECD, with promising feature filling performances. Similar results were obtained from the BDZ precursors. In this case, metallization was performed after electro-grafting, by deposition of metallic Pd.