Quantitative evaluation of the crystallinity of grain boundaries in polycrystalline materials

The effect of the crystllinity of electroplated copper thin films on their mechanical and electrical reliability was investigated experimentally. The crystallinity of grains and grain boundaries was evaluated by IQ (Image Quality) value of EBSD (Electron Back-Scattering Diffraction) analysis. Mechanical properties of thin electroplated films were measured by tensile test. The crystallinity of the thin film was improved by annealing. Therefore, yield stress decrease and fracture strain increase with increase of annealing temperature. Thin film interconnections for measurement of electrical properties were prepared based on damascene process. The crystallinity of the interconnection without annealing was low. The crystallinity of interconnection was improved by annealing at 400oC for 30minutes. Though the EM (Electro-Migration) resistance of the annealed film was improved drastically, SM (Stress-induced Migration) was activated even though interconnection was kept at room temperature without any application of electrical current after annealing. This is because high residual stress was caused by shrinkage of electroplated copper due to change of crystallinity. Thus the control of the crystallinity of the electroplated film was very important to improve the reliability of the interconnection.