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

Cu electroplating which emerges as a viable Cu filling technique for damasc ene processing relies on the presence of a smooth and continuous Cu seed la yer. Metal organic chemical vapor deposition (MOCVD) may be the most promis ing technique to deposit the Cu seed layer. Plasma pretreatment is widely u sed as a precleaning technique which is essential for the enhancement of Cu nucleation in Cu-MOCVD. New pretreatment techniques which can replace plas ma pretreatments are proposed in this paper. Pd sputtering, Pd-HF dipping o r 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 pla sma H-2 precleaning. Pd sputtering pretreatment is effective for a variety of barrier metals including Ta, TiN, TaN and TaSiN. The mechanism through w hich Cu nucleation is enhanced may be as follows: a thin Pd buffer layer fo rmed by sputtering shields the barrier metal substrate surface with adsorbe d oxygen atoms making Cu nucleation difficult and provides preferred sites for Cu nucleation. (C) 2001 Elsevier Science Ltd. All rights reserved.