Characterization of copper layers grown by electrochemical mechanical deposition technique

Abstract

Electrochemical mechanical deposition (ECMD) is a new method that has the ability to deposit planar copper films on nonplanar substrate surfaces. The technique involves electrochemical deposition (ECD) and simultaneous sweeping of the substrate surface with a planarization pad. In this study, we investigated if there were any fundamental differences in the crystallization mechanisms of copper layers grown by the ECD and ECMD techniques. Comparing the variation of the electrical resistivity values over time for films deposited by ECD and ECMD methods and stored at around 18 °C, we found that there were only slight differences in the incubation periods of self-annealing. The activation energies for recrystallization were found to be 0.71 and 0.61 eV for layers grown by the ECD and the ECMD techniques, respectively. The major difference between the ECD and ECMD films was found in the crystalline texture, with ECD layers having a higher degree of (111) preferred orientation compared to the ECMD layers in their as-deposited form. After annealing, the situation reversed, and the ECMD layers displayed a higher (111)/(200) ratio compared to the ECD layers. Differences in texture are believed to result from the mechanical action of the pad on the ECMD copper layers which interfere with and alter the orientation of the growing grains. After high-temperature annealing, ECMD Cu layer microstructure was found to display larger grain size and more fully developed twins indicative of more complete recrystallization.