Impact of Kr gas mixing in oxygen plasma etching of ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer films

Abstract

Oxygen plasma etching characteristics of ferroelectric poly͑vinylidene fluoride-trifluoroethylene͒ copolymer films are investigated. It was found in MFM ͑M: metal; F: ferroelectric͒ capacitors that plasma damage effects to the ferroelectric properties were insignificant when Au metal masks were used. On the contrary, C-V ͑capacitance versus voltage͒ characteristics were significantly degraded in plasma-etched MFIS ͑I: insulator; S: semiconductor͒ diodes. The origin of this phenomenon is speculated to be degradation of the SiO 2 / Si interface by energetic oxygen ions and then mixing of Kr gas to the oxygen plasma is attempted to decrease the plasma damage.Organic ferroelectrics such as poly͑vinylidene fluoridetrifluoroethylene͒ ͓p͑VDF-TrFE͔͒ have widely been investigated structurally 1,2 and electrically. 3-7 It has been reported that the polarization reversal time in a 50-nm-thick p͑VDF-TrFE͒ film is as fast as 500 ns at an electric field of 2 MV/ cm, 5 and that the coercive voltage ͑V c ͒ in a 60-nm-thick p͑VDF-TrFE͒ film is as low as 2 V, keeping the remanent polarization ͑P r ͒ larger than 10 C / cm 2 . 8 Fabrication of organic nonvoltage memory transistor has also been reported. 9 These organic ferroelectrics might also be used in fabrication of ferroelectric-gate Si transistors because of the following properties which are in contrast with those of oxide ferroelectric films such as Pb͑Zr, Ti͒O 3 ; ͑1͒ the crystallization temperature is so low ͑typically 140°C͒ that no interaction between the film and substrate nor interdiffusion of the constituent elements is expected, even if the film is crystallized on Si directly, and ͑2͒ even if an interfacial layer is inserted between the ferroelectric film and Si substrate unintentionally or intentionally since the dielectric constants of organic ferroelectrics are low ͑typically 10-15͒, the external voltage is effectively applied to the ferroelectric film, and thus low voltage operation of the memory device can be expected. To fabricate ferroelectric-gate transistors in small size, however, it is important to investigate degradation of the ferroelectric films during wet and dry etching processes. Thus, we investigate in this letter the ferroelectric and leakage current characteristics of MFM ͑M: metal; F: ferroelectric͒ capacitors and MFIS ͑I: insulator; S: semiconductor͒ diodes, before and after the films are etched by oxygen plasma.p͑VDF-TrFE͒ films with a composition ratio of 72: 28 wt % were prepared by a spin-coating method on Pt/ TiN / SiO 2 / Si structures at 3000 rpm for 15 s. The deposited layer was dried at 120°C for 5 min in air. These processes were repeated until the film thickness became approximately 100 nm. Finally, the dried films were annealed at 140°C in air. Then, Au top electrodes of 200 m in diameter were formed on the annealed films by thermal evaporation, and P-E ͑polarization versus electric field͒ and J-V ͑current density versus voltage͒ characteristics of the MFM capacitors were measured. Next, the p͑VDF-TrFE͒ films were etched in oxygen pl...

Printable Ferroelectric PVDF/PMMA Blend Films with Ultralow Roughness for Low Voltage Non‐Volatile Polymer Memory

“…[10,11] Recently, the thermal imprinting technique has been employed for the fabrication of micro-and/or nano-patterned of PVDF and PVDF-TrFE with smooth planar surface profiles for non-volatile memories. [12] Patterns are achieved when a ferroelectric molten film is pressurized and embossed with a pre-patterned mold.…”

Drain Current Characteristics of Ferroelectric Gate-All-Around Si Nanowire Transistors Based on Drift/Diffusion Transport Theory

“…In numerical calculation, we first assume that a Si nanowire with a diameter of 5 nm (a ¼ 2:5 nm) is surrounded by a 5-nm-thick poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] ferroelectric film (b ¼ 7:5 nm). Upon comparison with the experimental data, [28][29][30] we choose the following values for P(VDF-TrFE): P s ¼ 8 C/cm 2 , P r =P s ¼ 0:9, E C ¼ 400 kV/cm, and " F ¼ 12. The other parameters used in the calculation are n i ¼ 1:5 Â 10 10 cm À3 , T ¼ 300 K, " Si ¼ 11:8, L ¼ 1 m, and ¼ 300 cm 2 V À1 s À1 .…”

Approximate Analysis of Cylindrical Ferroelectric Capacitor and Derivation of Drain Current Characteristics in Ferroelectric Gate-All-Around Carbon Nanotube Transistor

“…In this equation, the linear polarization component in a ferroelectric film is included in the second term. Upon comparison with the experimental data, 20,21) we choose the following values for P(VDF-TrFE): P S ¼ 8 C/cm 2 , P r =P S ¼ 0:9, E C ¼ 400 kV/cm, and " F ¼ 12. We further assume that a P(VDF-TrFE) film with thickness t ¼ 5 nm is deposited on a CNT with d ¼ 1 nm and that the gate voltage is high enough to satisfy the condition that r EC > b.…”