Electromigration-induced extrusion failures in Cu/low-k interconnects

Electromigration experiments were conducted to investigate the thresholds required for electromigration-induced extrusion failures in Cu/low-k interconnect structures. Extrusions at the anode were observed after long periods of void growth. Characterization of failure sites was carried out using scanning and transmission electron microscopy, which showed that failures occurred through delamination at the interface between the silicon-nitride-based capping layer diffusion barrier and the underlying Cu, Ta liner, and interlevel dielectric (ILD) materials. This interface is subjected to near tensile (mode I) loading with a mode mixity angle between 4° and 7°, estimated using finite-element-method analysis, as electromigration leads to a compressive stress in the underlying Cu. Comparisons of the fracture toughness for interfaces between the capping layer and individual underlayer materials indicate that the extrusion process initially involves plane-strain crack propagation. As Cu continues to extrude, the c...

[1]  J. J. Clement,et al.  Modeling electromigration‐induced stress evolution in confined metal lines , 1995 .

[2]  Carl V. Thompson,et al.  Capillary instabilities in thin, continuous films , 1992 .

[3]  Chee Lip Gan,et al.  Experimental characterization and modeling of the reliability of three-terminal dual-damascene Cu interconnect trees , 2003 .

[4]  Micromechanical measurement of active sites on silicon nitride using surface free energy variation. , 2002, Ultramicroscopy.

[5]  Conyers Herring,et al.  Diffusional Viscosity of a Polycrystalline Solid , 1950 .

[6]  C. Lavoie,et al.  The physical properties of cubic plasma-enhanced atomic layer deposition TaN films , 2004 .

[7]  Christine Hau-Riege,et al.  Effects of active atomic sinks and reservoirs on the reliability of Cu∕low-k interconnects , 2008 .

[8]  S. Baker,et al.  The Effect of Oxygen on Adhesion of Thin Copper Films to Silicon Nitride , 2003 .

[9]  Kevin T. Turner,et al.  Mixed-mode interface toughness of wafer-level Cu–Cu bonds using asymmetric chevron test , 2008 .

[10]  Egon Matijević,et al.  Chemistry of silica , 1980 .

[11]  Terry Alford,et al.  Contact angle measurements for adhesion energy evaluation of silver and copper films on parylene-n and SiO2 substrates , 2003 .

[12]  E. S. Meieran,et al.  DIRECT TRANSMISSION ELECTRON MICROSCOPE OBSERVATION OF ELECTROTRANSPORT IN ALUMINUM THIN FILMS , 1967 .

[13]  Christine Hau-Riege,et al.  The effect of interlevel dielectric on the critical tensile stress to void nucleation for the reliability of Cu interconnects , 2004 .

[14]  Michael J. Miksis,et al.  Capillary instabilities in solid thin films: Lines , 1996 .

[15]  Baozhen Li,et al.  Line depletion electromigration characterization of Cu interconnects , 2004 .

[16]  A. Evans,et al.  Development of a test method for measuring the mixed mode fracture resistance of bimaterial interfaces , 1990 .

[17]  Stefan P. Hau-Riege,et al.  The Effects of the Mechanical Properties of the Confinement Material on Electromigration in Metallic Interconnects , 2000 .

[18]  C. J. Smithells,et al.  Smithells metals reference book , 1949 .

[19]  Shefford P. Baker,et al.  Thin films: Stresses and mechanical properties VI , 1997 .

[20]  Z. Suo,et al.  Mixed mode cracking in layered materials , 1991 .

[21]  J. Vlassak,et al.  Fracture of organosilicate glass thin films: environmental effects , 2005 .

[22]  M. Korhonen,et al.  Stress evolution due to electromigration in confined metal lines , 1993 .