The mechanical properties and deformation behaviors of copper with different grain sizes have been investigated in this study by instrumented nanoindentation. Following the Hall-Petch relation, the hardness of copper specimens increased as the grain size decreased. Dislocations were clearly observed in deformed regions around indent marks, indicating plastic deformation by dislocation formation and sliding. However, the hardness of electroless copper films with an ultrafine grain size of only 10 nm dropped. Voiding at grain boundaries and triple grain junctions was observed as a consequence of grain-boundary sliding and grain rotation, which was expected as the dominant deformation mechanism resulting in the reduced hardness. The critical shear stresses for the initiation of plastic deformation in the copper specimens with large grain sizes were close to the theoretical value and comparatively much lower for electroless copper films with an ultrafine grain size. (c) 2007 American Institute of Physics

The nanomechanical responses and interface adhesion of electrochemically plated copper ͑Cu͒ film have been investigated for the evaluation of interconnect reliability. The hardness and elastic modulus of the Cu film were measured by nanoindentation test as about 2.1 and 120 GPa, respectively. A dislocation burst phenomenon was observed and revealed the initiation of plastic deformation of the Cu film. The converted true stress-strain curve provided a stress criterion of 9.3 GPa for the plastic yielding of the Cu film. Besides, the creep behavior was also analyzed under nanoindentation test and showed a power law expression with a creep stress exponent of about 22. Moreover, the interfacial adhesion strength and delamination behavior between the Cu film and silicon carbide ͑SiC͒ etch stop layer have been studied using a four-point bending test. During delamination, cracks irregularly propagated along the Cu/SiC interface with blocking by the ductile Cu film. The fracture energy release rate for the delamination of Cu/SiC interface was measured as around 2-10 J/m 2 , affected by SiC deposition condition and testing parameter.Copper ͑Cu͒ with low electrical resistivity and high thermal conductivity has been widely adopted as multilevel interconnects in ultralarge-scale integrated ͑ULSI͒ circuits to reduce the problem of serious resistance-capacitance delay. 1 Copper metallization, mainly performed by electrochemical plating, has the advantages of low processing temperature, low cost, high throughput, good quality, and gap-filling capability, thus becoming attractive in the generation of 90 nm semiconductor manufacturing. 1-5 However, mechanical damages of the Cu films, such as film deformation and interface delamination caused by thermal stresses, chemical-mechanical polishing, or even wire bonding during chip packaging, severely suppress the processing yield and application reliability of microelectronic devices. 6-10 Film deformation and interface delamination detrimentally affect the performance of integrated circuits ͑ICs͒, especially with increasing integration density of ICs and thus increasing the amount of layer interface in the interconnect structures. A high resistance of the Cu films to the mechanical damages is thus strongly demanded to fit the strict requirements of next-generation semiconductor manufacturing. The true mechanical properties of the Cu films, including film strength and interface adhesion, therefore need to be clarified for the evaluation of the reliability of multilevel interconnects.However, due to the limit of conventional measurement equipment, the mechanical properties of nanoscale Cu thin films used in finely patterned interconnect structures have not been well studied. Nanomechanical analyses are required for further investigation of the true mechanical responses and deformation mechanisms of these thin films. An instrumented nanoindentation test has been widely applied for measurement of the hardness and elastic modulus of thin films and provides reliable results. 11,12 However, o...

Erratum: "Copper electroplating for future ultralarge scale integration interconnection" [J.

In this study, amorphous Ni-P films were deposited by electroless plating under different pH values. Their mechanical properties and deformation behavior were then investigated by instrumented nanoindentation. With increasing pH value of the plating solution from 3.75 to 6.0, the hardness and elastic modulus of the obtained Ni-P films increased from 6.1 GPa and 146 GPa to 8.2 GPa and 168 GPa respectively. From the load-indentation depth curve, the Ni-P films were found to yield at an indentation depth of 8 nm. By microstructural examination around the indented regions, early-stage plastic deformation of the amorphous Ni-P films was verified through the formation and extension of shear bands with a spacing of several tens of nanometers. Within the shear bands, flow dilatationinduced intense shear localization was expected and resulted in crystallization in the amorphous matrix. The critical shear stress and energy release rate required for the initiation of early-stage plastic yielding of the Ni-P films were calculated to be about 1.4 GPa and 3.0 J/m(2) respectively, both of which increased with pH values

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