Electromigration behavior of dual-damascene Cu interconnects--Structure, width, and length dependences

Abstract Experiments were performed to study the effect of line width and length, and the results revealed interesting differences in electromigration behavior of via-fed upper and lower layer dual-damascene test structures. The observed location of electromigration induced void in upper and lower layer test structures cannot be completely explained by the theory of current gradient induced vacancy diffusion. The electromigration median time to failure (MTF) were found to be dependent upon the line width for the lower layer test structures while it remained unaffected in the case of upper layer test structure. Cu/dielectric cap interface acting as the dominant electromigration path and the current crowding location being near the Cu/dielectric cap interface for lower layer structures due to structural differences, explain this behavior. Similarly, short length upper and lower layer test structures exhibited completely different characteristics. The back stress effect on short lines was evident on both upper and lower layer structures, however, only the upper layer showed two distinct via and line failure mechanisms. These observed effects are specific to Cu dual-damascene structures and can have major technological implications for electromigration reliability assessment.

[1]  Robert Rosenberg,et al.  Reduced electromigration of Cu wires by surface coating , 2002 .

[2]  S. Penka,et al.  Electromigration failure mechanism studies on copper interconnects , 2002, Proceedings of the IEEE 2002 International Interconnect Technology Conference (Cat. No.02EX519).

[3]  Daniel C. Edelstein,et al.  Copper Metallization for High Performance Silicon Technology , 2000 .

[4]  King-Ning Tu,et al.  Effect of current crowding on vacancy diffusion and void formation in electromigration , 2000 .

[5]  Paul S. Ho,et al.  Electromigration reliability issues in dual-damascene Cu interconnections , 2002, IEEE Trans. Reliab..

[6]  Ping-Chuan Wang,et al.  Electromigration threshold in copper interconnects , 2001 .

[7]  Paul S. Ho,et al.  Direct observation of a critical length effect in dual-damascene Cu/oxide interconnects , 2001 .

[8]  R. M. Bradley,et al.  STABILITY OF A CIRCULAR VOID IN A PASSIVATED, CURRENT-CARRYING METAL FILM , 1996 .

[9]  Joe W. McPherson,et al.  Stress-induced voiding under vias connected to wide Cu metal leads , 2002, 2002 IEEE International Reliability Physics Symposium. Proceedings. 40th Annual (Cat. No.02CH37320).

[10]  Robert Rosenberg,et al.  Mechanisms for very long electromigration lifetime in dual-damascene Cu interconnections , 2001 .

[11]  Chee Lip Gan,et al.  Length Effects on the Reliability of Dual-Damascene Cu Interconnects , 2002 .

[12]  Stefan P. Hau-Riege,et al.  Probabilistic immortality of Cu damascene interconnects , 2002 .

[13]  Chee Lip Gan,et al.  Effect of current direction on the lifetime of different levels of Cu dual-damascene metallization , 2001 .

[14]  Harold Gamble,et al.  Surface electromigration in copper interconnects , 2000 .

[15]  G. Reimbold,et al.  Evidence of grain-boundary versus interface diffusion in electromigration experiments in copper damascene interconnects , 2003 .

[16]  King-Ning Tu,et al.  Effects of contact resistance and film thickness on current crowding and the critical product of electromigration in Blech structures , 2001 .

[17]  Paul S. Ho,et al.  Electromigration critical length effect in Cu/oxide dual-damascene interconnects , 2001 .

[18]  King-Ning Tu,et al.  The effect of contact resistance on current crowding and electromigration in ULSI multi-level interconnects , 2003 .

[19]  Eduard Arzt,et al.  A model for the effect of line width and mechanical strength on electromigration failure of interconnects with “near-bamboo” grain structures , 1991 .