Study Of Si-based Ferroelectric Capacitors With Ni-Al Film

Ni-Al oxidation-resistant films have been deposited on Silicon by magnetron sputtering, on which Pt/PZT/LNO capacitors have been fabricated and investigated. Moreover, ferroelectric capacitors of Pt/ LNO /PZT/LNO/STO,Pt/PZT/LNO/SiO2/Si are also studied. In this work, various techniques, such as x-ray diffraction (XRD), reflection high-energy electron diffraction (RHEED), atomic force microscopy, four-probe measurement and ferroelectric tester have been employed to characterize the structure, the morphology, transport property of conductive film, and ferroelectric property of ferroelectric capacitor.The viability of Ni3Al material as oxygen diffusion conducting barrier is explored experimentally in this paper. It is found that Ni-Al film possesses very favorable properties of very smooth , highly oxidation-resistant, very dense, and small resistivity (2ⅹ10-6?m). Moreover, using Ni-Al as the barrier layer, we successfully fabricated Pt/PZT/LNO ferroelectric capacitor on Si substrate. Remanent polarization and coercive voltage of a typical capacitor measured at 5V are ~20.6μC/cm2 and ~1.9V, respectively.Impacts of LNO electrodes prepared under various temperatures or powers on the structural and physical properties of LNO/PZT/LNO ferroelectric capacitors have been studied.The results indicate that the higher the deposition temperature for LNO film, the better for ferroelectric properties, which may be attributed to both the better crystallinity and bigger grain size induced at the high deposition temperature. The resistivity of LNO film decreases rapidly below 250℃, and then increases very slowly with increase of the deposition temperature. RHEED results demonstrate that LNO/STO heterostructure can be epitaxially fabricated from 250℃to 400℃. At 5V, remanent polarization and coercive voltage of capacitor with LNO electrode prepared at 400℃measured are ~87μC/cm2 and ~ 2.54V, respectively.However, the properties of the LNO/PZT/LNO/STO capacitors do not depend on the LNO bottom electrodes prepared at various powers although obvious changes can be found from AFM images of the LNO films. It is found that all the surfaces of LNO films under different powers are dense and smooth.