Trifluoroethylene bond enrichment in P(VDF-TrFE) copolymers with enhanced ferroelectric behaviors by plasma fluorination on bottom electrode

Abstract

Abstract CF4 plasma treatment on n+-Si wafers as bottom electrodes (BEs) of poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) metal-ferroelectric-metal (MFM) capacitors has been investigated in this study. Prior to the fabrication of MFM capacitors, comprehensive material analyses are administered to identify the incorporation of fluorine atoms into P(VDF-TrFE) copolymers, revealing an enrichment in C2HF3 (trifluoroethylene) bonds and an improvement in the crystallinity of the film. The P(VDF-TrFE) MFM capacitors with CF4-plasma-treated n+-Si wafers show a shallower charge trapping level of 0.154–0.226 eV extracted from the Frenkel–Poole (F–P) emission at 213–273 K for the BE injection compared to that for the top electrode (TE) injection, which is ascribed to the passivation of deep traps by the fluorine atoms that diffused from the n+-Si wafers. Thus, asymmetric remanent polarization and a negative internal bias field are obtained because of the significant increase in the β-phase at the bottom of the P(VDF-TrFE) films. With the CF4 plasma treatment for 1 min, the P(VDF-TrFE) MFM capacitors demonstrate a remanent polarization (2Pr) of 6.58 µC/cm2, a coercive electric field (Ec) of 0.47 MV/cm and stability for more than 3 × 104 cycles with negligible fatigue, making the fluorine-incorporated P(VDF-TrFE) copolymers suitable for future high-performance nonvolatile memory applications.