| Copper has been recently used as an interconnecting material since it has high conductivity and good electromigration failure resistance. Recent studies show the close relationship between texture and reliability of Cu damascene interconnects. However, textural and microstructural evolutions of Cu damascene interconnects as function of substrate texture, current density, line width and annealing process are still not well understood.; At first, to understand the influence of substrate texture and electroplating conditions on the texture and surface morphology of Cu electrodeposits, three different polycrystalline copper specimens were used as substrates and electrodeposits were plated using different current densities. The mechanism of growth of Cu electrodeposits and the importance of smooth surface morphology were discussed.; To analyze the effect of line width and annealing process on textural and microstructural evolution of Cu damascene interconnects, Cu interconnects samples which have a different line width and different annealing process were investigated. According to x-ray diffraction (XRD) and electron backscattered diffraction (EBSD) results, the directional changes of (111) plane orientation with the different line width and annealing were observed. In addition, the analysis of microstructure and grain boundary character distribution (GBCD) of Cu damascene interconnects demonstrated that bamboo-like microstructure was developed in the narrow line and a polygranular structure was developed in the wider line. Also, the fraction of Sigma3 boundaries was changed depending on the line width and annealing process.; To analyze a relationship between the stress distribution and textural and microstructural evolution in the samples investigated, stress was calculated using finite element method (FEM), and these results were verified by physical stress simulation of copper in the Chapter 7. Through this investigation, it was found that the inhomogeneity of stress distribution in Cu damascene interconnects is an important factor which is necessary for understanding textural transformation after annealing, and the effects of stress on textural and microstructural evolution of Cu depends on the crystallographic texture and the annealing temperature.; A new interpretation of textural and microstructural evolution in Cu damascene interconnects lines after annealing and possible factors responsible for the texture transformation are suggested, and the optimum processing conditions are recommended. |
