Study of diffusion barrier properties of ionized metal plasma (IMP) deposited tantalum (Ta) between Cu and SiO2

The diffusion barrier properties of ionized metal plasma (IMP) deposited Ta between Cu and SiO2 have been investigated in the Cu (200 nm)/Ta (30 nm)/SiO2 (250 nm)/Si multi-layer structure. The IMP-Ta thin film shows better Cu diffusion barrier properties than CVD (chemical vapor deposition) and conventional PVD (physical vapor deposition) deposited Ta film. The thermal stability was evaluated by electrical measurement and X-ray diffraction (XRD) analysis. As a main part of thermal stability studies, the atomic intermixing, new compound formation and phase transitions in the test structure were also studied. Furthermore, a failure mechanism was also examined by XRD, scanning electron microscopy (SEM), secondary ion mass spectroscopy (SIMS) and Rutherford backscattering spectroscopy (RBS) in conjunction with electrical measurements. The 30 nm thick IMP-Ta was found to be stable up to 650°C for 35 min.