IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Electronics Tuesday Sessions
       Session EL-TuP

Paper EL-TuP31
Preferred Growth of Cu Thin Films on Ta and TaN@sub x@ Diffusion Barriers

Tuesday, October 30, 2001, 5:30 pm, Room 134/135

Session: Electronic Materials Poster Session
Presenter: J.H. Wang, National Tsing Hua University, Taiwan, R.O.C.
Authors: J.H. Wang, National Tsing Hua University, Taiwan, R.O.C.
J.C. Hu, National Tsing Hua University, Taiwan, R.O.C.
L.J. Chen, National Tsing Hua University, Taiwan, R.O.C.
Z.C. Lu, United Microelectronics Corporation, Taiwan, R.O.C.
C.S. Hsiung, United Microelectronics Corporation, Taiwan, R.O.C.
W.Y. Hsieh, United Microelectronics Corporation, Taiwan, R.O.C.
T.R. Yew, United Microelectronics Corporation, Taiwan, R.O.C.
Correspondent: Click to Email
Ta and TaN@sub x@ films have recently been extensively investigated to substitute for TiN films as an adhesion and diffusion barrier in Cu metallization for ultralarge-scale integrated applications. The electromigration resistance is sensitive to the texture of Cu films. Seeding and controlled growth of Cu films on the underlaying Ta and TaN@sub x@ films might be beneficial in achieving the desired texture of Cu films. In the present work, a series of textured growth of Cu films on the Ta and TaN@sub x@ with varying x was investigated. The phases formed in Ta and TaN@sub x@ films deposited with pure Ar, 10%, 20%, 30%, 40%, 50%, and 60% N@sub 2@/Ar ratios were found to be a mixture of @beta@-Ta and bcc-Ta, bcc-Ta, bcc-TaN@sub 0.1@, expanded bcc-TaN@sub 0.1@, hcp-Ta@sub 2@N, fcc-TaN, and fcc-TaN (nearly amorphous), respectively. The results indicated that the N atoms in Ta and TaN@sub x@ films occupied the interstitial sites of the crystal lattice. Solubility of N atoms in bcc-Ta films is low. The lattice in the vicinity of each atom is severally strained to accommodate the interstitial N atoms. As a result, the structures of bcc-TaN@sub 0.1@ and expanded bcc-TaN@sub 0.1@ are highly distorted. Moreover, the crystal structure of TaN@sub x@ films was found to change from bcc to fcc with increasing N content. A larger interstitial spacing in fcc lattice is capable of accommodating more N atoms in the Ta and TaN@sub x@ lattice. On the other hand, the growth of Cu was found to depend strongly on the microstructures of the Ta and TaN@sub x@ underlayers. The Cu (111)/(200) intensity ratio decreased with the concentration of N in Ta and TaN@sub x@ films. The results are explained in terms of the strained structures of bcc-TaN@sub 0.1@ and poor crystallinity of hcp-Ta@sub 2@N and fcc-TaN.