Integration of perovskite Pb[Zr0.35Ti0.65]O3/HfO2 ferroelectric-dielectric composite film on Si substrate

Abstract

PurposeThe purpose of this paper is to investigate the effect of high-k material HfO2 as a buffer layer for the fabrication of metal-ferroelectric-insulator-silicon (MFeIS) structures on Si (100) substrate.Design/methodology/approachRF-sputtered Pb[Zr0.35Ti0.65]O3 or (PZT) and plasma-enhanced atomic layer deposited HfO2 films were selected as the ferroelectric and high-k buffer layer, respectively, for the fabrication of metal-ferroelectric-insulator-silicon (MFeIS) structures on Si (100) substrate. Multiple angle ellipsometry and X-ray diffraction analysis was carried out to obtain the crystal orientation, refractive index and absorption coefficient parameters of the deposited/annealed films. In the different range of annealing temperature, the refractive index was observed in the range of 2.9 to 2 and 1.86 to 2.64 for the PZT and HfO2 films, respectivelyFindingsElectrical and ferroelectric properties of the dielectric and ferroelectric films and their stacks were obtained by fabricating the metal/ferroelectric/silicon (MFeS), metal/ferroelectric/metal, metal/insulator/silicon and MFeIS capacitor structures. A closed hysteresis loop with remnant polarization of 4.6 µC/cm2 and coercive voltage of 2.1 V was observed in the PZT film annealed at 5000 C. Introduction of HfO2 buffer layer (10 nm) improves the memory window from 5.12 V in MFeS to 6.4 V in MFeIS structure with one order reduction in the leakage current density. The same MFeS device was found having excellent fatigue resistance property for greater than 1010 read/write cycles and data retention time more than 3 h.Originality/valueThe MFeIS structure has been fabricated with constant PZT thickness and varied buffer layer (HfO2) thickness. Electrical characteristics shows the improved leakage current and memory window in the MFeIS structures as compared to the MFeS structures. Optimized MFeIS structure with 10-nm buffer layer shows the excellent ferroelectric properties with endurance greater than E10 read/write cycles and data retention time higher than 3 h. The above properties indicate the MFe(100 nm)I(10 nm)S gate stack as a potential candidate for the FeFET-based nonvolatile memory applications.