AVS 47th International Symposium
    Electronics Tuesday Sessions
       Session EL-TuP

Paper EL-TuP1
Polarization Effect on Copper Electroplating in Presence of Thiourea Additives

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: C.-L. Cheng, Chung-Yuan University, Taiwan
Authors: C.-L. Cheng, Chung-Yuan University, Taiwan
Y.-S. Lin, Chung-Yuan University, Taiwan
Correspondent: Click to Email
Copper metallization will play an important role in future microelectronic processing because Cu has lower resistivity and higher electromigration resistance compared to Al. Copper could be deposited by either physical sputtering, chemical vapor deposition (CVD), or electrochemical deposition. Since electroplating has advantages of low processing temperature, short processing time, and simple deposition facilities, which compared to traditional sputtering and CVD, electroplating becomes the most attractive techniques implemented in Cu metallization. Polarization becomes very important in Cu electroplating because it could effect formation of copper grain and copper filling mechanism. One common method to change the degree of polarization is using chemical additives during electroplating. In order to realize polarization effect on copper formation during electroplating, we choose a series of thiourea additives: thiourea, N-acetylthiourea, and N,N-diethylthiourea used as chemical additives on copper electroplating. Since N,N-diethylthiourea has a pair of electron-pushing groups (di-ethyl groups), it could enhance electron density around sulfur atom to increase interaction with copper ions and make polarization higher. The results are shown polarization will become higher when N,N-diethylthiourea is present and lower when N-acetylthiourea (electron puller) is existed. The finer grain size of copper forms when the higher polarization appears. Based on this study, we demonstrate that N,N-diethylthiourea could be used to act as gap filling promoters without void formation in the 0.25 micrometer dimension of trench with an aspect ratio of 4.