Thermal stress evolution in embedded Cu/low-k dielectric composite features

To determine the effect of low-modulus materials on the thermal stress evolution within interconnect metallization, thermal and residual stresses in copper features, embedded in an organosilicate glass (SiCOH) on a silicon substrate, were measured by x-ray diffraction as a function of temperature and calculated using finite element modeling. The elastic response of the structures was dictated by the thermal expansion mismatch between copper and silicon, the copper and SiCOH elastic moduli, and the composite geometry. The presence of a low-modulus layer between the features and underlying substrate plays a major role in the elastic stress relaxation generated during thermal cycling. © 2006 American Institute of Physics.