| As device dimensions shrink, there is an urgent need to replace conventionally used Al interconnects to achieve increased current density requirements and better performance at future technology node. Copper is a viable candidate due to its lower resistivity and higher resistance to electromigration. However, Cu has its own problems in its integration. It diffuses rapidly through SiO 2, Si and Ge into the active regions of the device, thereby deteriorating device performance. There is therefore a need to find a diffusion barrier for Cu.;Amorphous ternary nitrides are investigated as a candidate diffusion barrier for Cu metallization on single crystal Si and Ge substrates. Ge was chosen as a third element in the binary matrix of WNx, HfN x and TaN due to its chemical similarity to Si and possible integration in SiGe or Ge based devices. The addition of Ge helps in amorphization of the binary matrix. It hinders grain boundary formation and increases the recrystallization temperature compared to their respective binary nitrides. Cu was deposited in-situ after nitride deposition. In the case of W-Ge-N on Si, the recrystallization temperature was raised by 400°C, while for Ta-Ge-N it was raised by 100°C indicating better diffusion barrier properties than their corresponding binaries.;A bilayer approach for diffusion barrier was also studied. Ge/HfN x bilayer was deposited on Si followed by in-situ deposition of Cu. Copper reacts with Ge and forms Cu3Ge which has low resistivity, is less reactive with oxygen, and is a diffusion barrier for Cu. By combining the material properties of Cu3Ge and HfNx, an excellent diffusion barrier performance was demonstrated under stringent test conditions. |
