Effects of BEOL stack on thermal mechanical stress of Cu lines

The measurement and control of the stress state in BEOL interconnects are important to ensure structural integrity and long term reliability of integrated circuits. Thermal stress in interconnects is determined by the thermalmechanical properties of Cu lines, substrate, and dielectric materials. The effect of BEOL stacks on thermal stress characteristics of Cu lines were investigated using X-ray diffraction stress measurements. The stress characteristics of M1 and M4 level interconnects in full low-k and low-k/oxide hybrid dielectric stacks were evaluated, and the results indicated reduced substrate confinement and an increased impact of the dielectric material on in-plane stresses in higher level interconnects. The effects of dielectric stack and material properties were examined and the implication in the stresses of multilevel interconnects are discussed. © 2006 Materials Research Society.