Investigation Of Ni-al Barrier Layer For Integrating Si-based Ferroelectric Capacitors With Copper

It is crucial to find an appropriate diffusion barrier for Cu interconnection technology; therefore, it is very important for investigating the failure mechanism of the barrier layer in order to increase its reliability. The Cu/Ni-Al/SiO2/Si, Cu/Ni-Al/Si, and Cu/Ta/Ni-Al/Si heterostructure are prepared at room temperature by magnetron sputtering method and annealed in an ultra-high vacuum system. Sheet resistance, x-ray diffraction, atomic force microscopy and high resolution transmission electron microscopy are used to study the microstructures, transport properties, surface morphology and interfaces of the samples. It is found that no obvious reactions or interdiffusion occur in the Cu/Ni-Al/SiO2/Si and Cu/Ni-Al/Si samples annealed at 750℃, and no Cu silicide is observed for Cu/Ta/Ni-Al/Si samples annealed at 800℃. All the Ni-Al film of the samples keep amorphous. Both the Ni-Al(5 nm) and the Ta (3 nm)/Ni-Al (3 nm) bilayer films are excellent diffusion barrier for Cu metallization.Based on the diffusion equation and fick's second law, we calculated the activation energy to study the barrier properties. Ea for Ni-Al film is 2.9 eV, indicating Ni-Al film has good barrier property. The microstructure of the barrier materials impacts the performance of the barrier layer for Cu diffusion barrier. Amorphous Ni-Al film can be used as good barrier layer since it lacks grain boundaries, which can act as the high diffusivity path.La0.5 Sr0.5CoO3 (LSCO)/Pb(ZrxTi1-x)O3 (PZT)/La0.5Sr0.5CoO3 (LSCO) ferroelectric capacitor has been integrated on Cu/Ni-Al/Si substrate by combining Sol-Gel and magnetron sputtering methods. Ferroelectric properties are studied by a ferroelectric tester. It is found that the hysteresis loop is well saturated at 12V. Moreover, the capacitor has low coercive voltage, high remnant polarization, low leakage current density.