Cladded Silver and Silver Alloy Metallization for Improved Adhesion and Electromigration Resistance

Terry Alford (Inventor)

Research output: Patent


Continuous shrinkage in device dimensions in ultra-large-scale-integration (ULSI) technologies has resulted in interconnects being subjected to high current densities and thermal stresses leading to their premature failure. Electromigration is one of the governing phenomenon which contributes to early failure of interconnects. Choice of metallization is an important parameter that affects the performance of chip interconnects. Until recently, aluminum (Al) was considered as the ideal interconnect metallization but its. relatively high resistivity (~2.7 mW-cm) and poor electromigration resistance have led to an ongoing search for a better replacement. Silver (Ag) is one of the potential candidates for replacement of Al as interconnect metallization due to its lowest bulk resistivity (1.6 mW-cm) compared to other potential interconnect materials and excellent electromigration resistance. However, Ag tends to agglomerate at higher temperatures, and does not adhere too well to dielectrics due to its inert nature when in contact with most materials. The clad structure being proposed here will alleviate the problem of adhesion and agglomeration observed in pure Ag films and it is being put forth as a replacement for Al and Cu interconnect metallization in the microelectronics industry because of the reasons listed below: a) Less processing steps b) Lower overall resistancec) Better electromigration resistance because according to previous study the activation energies of pure Ag (0.58 eV) and Cu (0.67 eV) metallizations are similar thus their failure times would also be similar [M. Hauder, J. Gstottner, W. Hansch, and D. Scmitt-Landsiedel, Appl. Phys. Lett., 78, 838 (2001)]. However, as has been shown experimentally in this study the failure time of the clad structure is 38 times better than that of pure Ag thus leading to the conclusion that the electromigration resistance of the proposed metallization structure would also be better than that of Cu.
Original languageEnglish (US)
StatePublished - Jul 30 2004


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