Abstract
With the evolution of VLSI process technology, the continuous shrinkage device feature size leads to an increase in the density of integrated circuits (ICs). The effect of RC delay in ICs will become significant and limit the advance of process technology. Traditional Al metallization can not meet the demand and will be replaced by Cu metallization, due to the advantages of low resistivity and high electromigration resistance. However, the characteristic of Cu oxidation may seriously damage the reliability of Cu interconnects. The effect of oxidation in Cu wiring is an important problem and need to be solved in the future development of Cu process technology. In the experiment the in-situ resistivity measurement was utilized to study the oxidation kinetics of Cu thin films. The relation between the change of Cu thin film resistance as a function of annealing temperature and time was investigated. The temperature dependence of Cu oxidation kinetics was also discussed. The experimental results show that the resistance of Cu thin films with lousy microstructure which were annealed below 100°C will drop parabolically with increasing annealing time, but decreased slightly for dense Cu thin films. Both two samples did not show obvious oxidation. In addition, when Cu is annealed below 200°C in atmosphere, the activation energy of Cu oxide growth was found to be 0.85 0.09eV according to the oxide thickness calculated from the resistance curve with respect to time. It seems that diffusion control would be the primary mechanism for Cu oxidation in atmosphere, and reaction control in dry O2. Therefore, Cu oxide formation mechanism may change or have a mixed control mechanism in different environments. Finally, the XRD analysis revealed that the Cu oxides were found to be Cu2O at low oxidation temperature for both Cu samples. Besides, the SEM observation indicated that the Cu oxide grew up with isolated island shape, which agrees with the literature reported.