Preparation and Characterization of Pb(Zr,Ti)O₃ Films Deposited on Pt/RuO₂ Hybrid Electrode for Ferroelectric Random Access Memory Devices

Abstract

Polycrystalline Pb(Zr,Ti)O 3 (PZT) films were fabricated at a low temperature of 450 • C by the electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD) method. Stoichiometric PZT films with the pure perovskite phase could be obtained over a wider range of deposition conditions on Pt/RuO 2 hybrid electrodes than on RuO 2 electrodes. PZT capacitors fabricated on Pt/RuO 2 hybrid electrodes showed low leakage current and superior polarization characteristics compared with those on RuO 2 electrodes. PZT capacitors fabricated on Pt/RuO 2 were not as fatigue-free as those on RuO 2 but had higher resistance to fatigue than those on Pt. The introduction of a PbTiO 3 buffer layer prior to PZT film deposition on Pt/RuO 2 improved the fatigue characteristics by suppressing the formation of nonstoichiometric interfacial layers. Good leakage current property (J : 5.8 × 10 −7 A/cm 2 at 200 kV/cm) and fatigue characteristic (P * − P ∧ : 9% drop after 4 × 10 9 fatigue cycles) could be obtained for the 110-nm-thick PZT film using Pt/RuO 2 hybrid top and bottom electrodes. This electrode structure is thought to be promising for use as a capacitor of high-density ferroelectric random access memory (FRAM) devices. The fatigue model that can explain the fatigue characteristics of PECVD-PZT capacitors with various hybrid electrode configurations is also suggested.

A Study on the Crystalline Orientation and Electromechanical Properties of PZT and Doped PZT Thin Films by Using the Sol-Gel Method

“…3. The leakage current characteristics of all PZT capacitors were almost independent of the polarity of the applied voltage, which suggests that the leakage current characteristics were affected mainly by the bulk characteristics of PZT films rather than the interfaces between the PZT films and the electrodes [6]. A variation in the characteristics was slightly observed.…”

Strongly Enhanced Piezoelectric Response in Lead Zirconate Titanate Films with Vertically Aligned Columnar Grains

“…The physical methods include sputter deposition, 27−29 pulsed laser deposition (PLD), 30−33 molecular beam epitaxy (MBE), 34 and evaporation. 35,36 The chemical methods are metal–organic chemical vapor deposition, 37,38 plasma enhanced chemical vapor deposition, 39,40 and sol–gel processing. 41−45 Each deposition technique has its intrinsic advantages and disadvantages.…”

Giant magnetoresistive structures based on CrO2 with epitaxial RuO2 as the spacer layer

“…[7][8][9] Recent studies have also demonstrated its utility as a contact electrode material in ferroelectric random access memory devices that offer superior polarization fatigue properties with very low leakage current. [10][11][12] Band structure calculations suggest that heterostructures fabricated with CrO 2 / RuO 2 / CrO 2 can possibly exhibit significantly enhanced magnetoresistance ͑MR͒ resulting from the near complete spin polarizations of CrO 2 . 13 In addition, our results demonstrate that the subsequent RuO 2 deposition on top of CrO 2 removes the Cr 2 O 3 insulating barrier, resulting in a highly conductive interface.…”