Enhancement of Cu nucleation in Cu-MOCVD by Pd sputtering pretreatment

Cu electroplating which emerges as a viable Cu filling technique for damascene processing relies on the presence of a smooth and continuous Cu seed layer. Metal organic chemical vapor deposition (MOCVD) may be the most promising technique to deposit the Cu seed layer. Plasma pretreatment is widely used as a precleaning technique which is essential for the enhancement of Cu nucleation in Cu-MOCVD. New pretreatment techniques which can replace plasma pretreatments are proposed in this paper. Pd sputtering, Pd-HF dipping or Pd-CVD pretreatment will possibly enhance Cu nucleation significantly if it is conducted on barrier metal films prior to Cu-MOCVD. It was found that Pd sputtering is more effective in enhancing Cu nucleation than direct plasma H-2 precleaning. Pd sputtering pretreatment is effective for a variety of barrier metals including Ta, TiN, TaN and TaSiN. The mechanism through which Cu nucleation is enhanced may be as follows: a thin Pd buffer layer formed by sputtering shields the barrier metal substrate surface with adsorbed oxygen atoms making Cu nucleation difficult and provides preferred sites for Cu nucleation. (C) 2001 Elsevier Science Ltd. All rights reserved.