Comparative study of copper films prepared by ionized metal plasma sputtering and chemical vapor deposition in the Cu/TaN/SiO2/Si multilayer structure

This work investigated the properties of ionized metal plasma (IMP) deposited copper (Cu) and chemical vapor deposited (CVD) Cu on IMP-TaN (tantalum nitride) diffusion barrier in the Cu(200 nm)/TaN(30 nm)/SiO₂(250 nm)/Si multi-layer structure. The IMP-Cu film deposited on IMP-TaN had a preferred orientation (220) with a grain size of around 30 nm and roughness (RMS) of 1.391 nm, while the CVD-Cu had a (111) preferred orientation with a grain size around 170 nm and roughness (RMS) of 15.416 nm as determined by atomic force microscopy (AFM) and x-ray diffraction (XRD) analyses. Thermal stability study of the structures was also performed by sheet resistance measurements, scanning electron microscopy (SEM), XRD and Rutherford backscattering spectroscopy (RBS). These results revealed that IMP-Cu on IMP-TaN has higher thermal stability, less intermixing and/or agglomeration than CVD-Cu on IMP-TaN at the same annealing temperatures. The higher thermal stability of IMP-Cu than CVD-Cu can be accounted by their difference in microstructure. The failure mechanisms of IMP-Cu and CVD-Cu in multiplayer structure were also discussed.