| With the development of submicron and nanometer integrated circuits (ICs), the size of interconnects continues to decrease, which dramatically influences the ICs service reliability. The decreasing size results in an increasing resistivity of interconnects, which intensifies RC delay. Moreover, the shrinking size gives rise to a higher current density, causing electromigration in interconnects. The Cu and Ta films have received wildly attention as interconnect and diffusion barrier materials. The Cu and Ta films with different thickness and grain size were prepared by DC magnetron sputtering. The microstructure of the thin films was characterized through SEM, XRD, TEM, and AFM. The electric properties of the thin films, such as resistivity and electromigration, were measured by use of four-point probe measurement system and physical properties measurement system. The main researching results are as follows,The resistivity of Cu films with different size at room temperature and in the temperature range of50K to400K was investigated. The resistivity of Cu films with different thickness and grain size increases obviously when the size decreases, and grain boundary scattering plays a dominant role. In the temperature range of50K to400K, the resistivity of Cu films increases with the temperature. For the same thickness Cu films, the temperature coefficient of resistivity (TCR) reduces with the decrease of grain size, since grain boundary scattering varies with temperature. The electric properties of Cu-Ta films were studied. The resistivity and the TCR of Cu films increase due to Cu-Ta interfaces. The resistivity of Cu films has a maximum and a minimum at the temperature below100K.The electromigration about Cu-Ta films was also investigated. It is found that the resistance of thinner Cu’films increase more than thicker ones at the same temperature.40nm thick Cu film has a30%increase in resistance at350K. |
