Isothermal stress relaxation in electroplated Cu films. II. Kinetic modeling
نویسندگان
چکیده
In Part I we reported experimental results obtained from isothermal stress relaxation tests of electroplated Cu thin films with and without a passivation layer and deduced grain-boundary and interface diffusivities based on a kinetic model. Here in Part II we describe the detail of the model, which is based on coupling of grain-boundary diffusion with surface diffusion for unpassivated films and with interface diffusion for passivated films. Numerical solutions are obtained for the coupled diffusion problems and analytical solutions are obtained for several limiting cases. The effects of surface diffusivity and interface diffusivity on stress relaxation of polycrystalline thin films are analyzed and compared with experiments. The model predicts a transient behavior of stress relaxation and provides a quantitative correlation between stress relaxation and the kinetics of mass transport. In particular, the models can be used together with isothermal stress relaxation tests to characterize interface diffusion and to evaluate selected cap layers for improving electromigration reliability of Cu interconnects. © 2005 American Institute of Physics. fDOI: 10.1063/1.1904721g
منابع مشابه
Isothermal stress relaxation in electroplated Cu films. I. Mass transport measurements
Recent studies on Cu interconnects have shown that interface diffusion between Cu and the cap layer dominates mass transport for electromigration. The kinetics of mass transport by interface diffusion strongly depends on the material and processing of the cap layer. In this series of two papers, we report in Part I the interface and grain-boundary mass transport measured from isothermal stress ...
متن کاملEffects of Passivation Layer on Stress Relaxation and Mass Transport in Electroplated Cu Films
Recent studies have shown that the Cu/cap layer interface is the dominant diffusion path for electromigration (EM) in Cu interconnects, making it important to develop effective methods to evaluate the effect of passivation layer on interfacial mass transport and EM lifetime for Cu interconnects. This work shows that a set of isothermal stress relaxation tests together with appropriate modeling ...
متن کاملEffect of passivation on stress relaxation in electroplated copper films
The present study investigated the effect of passivation on the kinetics of interfacial mass transport by measuring stress relaxation in electroplated Cu films with four different cap layers: SiN, SiC, SiCN, and a Co metal cap. Stress curves measured under thermal cycling showed different behaviors for the unpassivated and passivated Cu films, but were essentially indifferent for the films pass...
متن کاملThe Mechanical Properties of Electroplated Cu Thin Films Measured by means of the Bulge Test Technique
The mechanical properties of freestanding electroplated Cu films were determined by measuring the deflection of Si-framed, pressurized membranes. The films were deformed under plane-strain conditions. The pressure-deflection data are converted into stress-strain curves by means of simple analytical formulae. The microstructure of the Cu films was characterized using scanning electron microscopy...
متن کاملResidual Stress and Microstructure of Electroplated Cu Film on Different Barrier Layers
Copper films of different thicknesses between 0.2 and 2 microns were electroplated on adhesion-promoting TiW and Ta barrier layers on <100> single crystal 6-inch silicon wafers. The residual stress was measured after each processing step using a wafer curvature technique employing Stoney’s equation. Large gradients in the stress distributions were found across each wafer. Controlled Cu grain gr...
متن کامل