Fabrication of Polycrystalline Ferroelectric Gate FET Memory with an Intermediate Electrode
We fabricated a new ferroelectric gate field-effect transistor memory (F-FET) with an intermediate electrode inserted between the ferroelectric capacitor (Cf) and the metal-oxide-semiconductor field-effect transistor (MOSFET) for writing data. The structure was a RuO2 top electrode/polycrystalline ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT)/(Pt/RuO2) intermediate electrode/SiO2/Si substrate. The basic operation of the new memory was confirmed by a discrete circuit that the Cf was connected serially with the MOSFET. For data writing, two positive or negative square pulses applied between the top electrode and the intermediate electrode induced the positive (Pr+) and the negative (Pr-) remanent polarizations, respectively, for coding memory states. For data reading, an unipolar square pulse train was applied between the top electrode and the source of the MOSFET, and the drain of the MOSFET was biased by a DC voltage. When the memory state corresponded to the Pr+ or the P-, the drain current (ID) was small or large, respectively. In this study, we used a polycrystalline PZT film to deal with the difficult problems of an epitaxial PZT film such as complicated techniques and high cost of products for commercialization goal.
Analysis on operation of a F-FET memory with an intermediate electrode
An operation model of a ferroelectric gate field-effect transistor memory with an intermediate electrode was proposed and analyzed. Read endurance characteristics of the memory during a consecutive reading was simulated using this model. The simulation results showed good agreement with the experimental data.
Crystal and Electrical Characterizations of Oriented Yttria-Stabilized Zirconia Buffer Layer for the Metal/Ferroelectric/Insulator/Semiconductor Field-Effect Transistor
Using reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD) and X-ray pole figure measurements, we evaluated the crystallinities of yttria-stabilized zirconia (YSZ) thin films as an intermediate layer for metal/ferroelectric/insulator/semiconductor-structure field-effect transistors (MFIS-FETs). A highly oriented YSZ film was grown on a Si(100) substrate by the vacuum evaporation method. The [100] axes of the YSZ crystals were aligned parallel to [100] axes of Si crystals in the plane. In addition, electrical characterizations of the highly oriented YSZ thin films on Si(100) were evaluated from current–voltage ( I–V ) and capacitance–voltage ( C–V ) measurements. The I–V measurement indicated a breakdown field of about 3 MV/cm (at I=1 nA/cm2). The C–V measurement results suggest that mobile ions were present in the YSZ films. Oriented perovskite PbTiO3 films were deposited on YSZ crystal and YSZ/Si(100) substrates by the digital chemical vapor deposition (CVD) method. These PbTiO3 films included many PbTiO3 grains with their [100] axes parallel to the [100] or [110] axis of YSZ crystals in the plane of the PbTiO3/YSZ interface.