Electric Properties of PVDF-TrFE (75/25) Thin Films with a Lanthanum Zirconium Oxide Buffer Layer for FeRAM

Metal-ferroelectric-insulator-semiconductor capacitors, using polyvinylidene fluoride trifluoroethylene (P(VDF-TrFE)) as a ferroelectric layer and lanthanum zirconium oxide (LaZrOx) as an insulator layer, were fabricated on a p-type Si (100) substrate. We prepared the films by using a spin-coating method. From the C-V characteristics of the LaZrOx/Si structure, we observed negligible hysteresis. The equivalent oxide thickness (EOT) was about 7.9 nm. We, then, spin-coated the P(VDF-TrFE) films on the LaZrOx/Si structure by using various solutions with different concentrations (1, 3, and 5 wt%). The P(VDF-TrFE) was crystallized at 165 degrees C for 30 minutes. The memory window width in the C-V (capacitance-voltage) curve of the Au/P(VDF-TrFE)/LaZrOx/Si structure was about 2 V for a, voltage sweep of +/- 5 V. The memory window width increased as the thickness of the P(VDF-TrFE) film increased. The value of the leakage current density at 5 V was about 3.5 x 10(-8) A/cm(2) for the thick film from the 5-wt% solution. From these results, we expect the combination of P(VDF-TrFE) and a LaZrOx thin film to be both useful and promising for a ferroelectric random access memory operating at a low voltage.