Scaled PLZT Thin Film Capacitors with Excellent Endurance and Retention Performance

2000 ◽  
Vol 655 ◽  
Author(s):  
Fan Chu ◽  
Glen Fox ◽  
Tom Davenport
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Low Voltage ◽  
Volatile Component ◽  
Retention Performance ◽  
Ceramic Thin Films ◽  
Thin Film Capacitors ◽  
Pzt Thin Film ◽  
Plzt Thin Film ◽  
Plzt Thin Films

AbstractThe requirements for future ferroelectric non-volatile memories (FRAM) include lower operating voltages, higher densities and tighter design rules. In order to achieve these requirements the key component of the FRAM device, viz., the PbZrxTi1划xO3 (PZT) thin film capacitor must be scaled dimensionally to obtain reduced film thickness and capacitor area. This paper presents the ferroelectric performance of RF magnetron sputtered PLZT thin films with thickness scaled down to 1000Å. The switching performance of the thickness scaled PLZT thin films meets the requirements of 1.8V FRAM device. Though PLZT ceramic thin films, of which the fatigue is often a concern, are utilized as non-volatile component, excellent fatigue performance was observed. The scaled PLZT thin film capacitors are fatigue free up to 1011 fatigue cycles (E=200kV/cm). The scaled 1000Å PLZT thin films also showed good imprint performance. The opposite-state charge after 10 years baking at 150°C was still above the sensing level. The thickness scaled PZT thin films, showing dramatically improved ferroelectric performance, can be applied to the manufacturing of low voltage FRAM products.

Polarization Relaxation in Pzt/Plzt Thin Film Capacitors

1996 ◽  
Vol 433 ◽  
Author(s):  
Bo Jiang ◽  
Venkatasubramani Balu ◽  
Tung-Sheng Chen ◽  
Shao-Hong Kuah ◽  
Jack C. Lee
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Current Density ◽  
Remanent Polarization ◽  
Time Range ◽  
Polarization Current ◽  
La Doping ◽  
Thin Film Capacitors ◽  
Plzt Thin Film ◽  
Plzt Thin Films

AbstractPolarization relaxation in PZT and PLZT (with La concentration from 0% to 10%) thin film capacitors was characterized in the time range from 10 ns to 1000 s. It was found that at zero volt the polarization in PZT and PLZT thin films changes logarithmically with time, P(t) = blog(t) + P0, and the polarization current density J(t) = dP(t)/ dt obeys the Curie-von Schweidler Law, J(t) = b. t−x, with n = 1 from 100 ns extending to 10 s. Over 10 s, the exponent n in the J-t relationship becomes less than 1. The coefficient b in the Q-t and J-t relationship at zero volt correlates strongly with the remanent polarization. La doping in PZT reduces remanent polarization and reduces relaxation.

Basic Thin Film Process for Perovskite Ferroelectric Materials

1990 ◽  
Vol 200 ◽  
Author(s):  
Hideaki Adachi ◽  
Kiyotaka Wasa
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Rf Magnetron Sputtering ◽  
Ferroelectric Materials ◽  
Epitaxial Thin Films ◽  
Preparation Process ◽  
Film Preparation ◽  
Plzt Thin Film ◽  
Plzt Thin Films ◽  
Ferroelectric Perovskite

ABSTRACTThin film process for ferroelectric perovskite oxides has been investigated. Amorphous, polycrystal, and epitaxial thin films of Pb-based perovskite ferroelectrics were prepared by rf-magnetron sputtering, and their properties were discussed. Epitaxial PLZT thin films showed similar dielectric properties as PLZT bulk ceramics and also showed strong electrooptic effect. For further investigation, film preparation process was developed by multitarget sputtering and quaternary PLZT thin film with excellent epitaxial crystallinity was realized by using a graded composition layer.

Contribution of electrodes and microstructures to the electrical properties of Pb(Zr0.53Ti0.47)O3 thin film capacitors

1994 ◽  
Vol 9 (11) ◽  
pp. 2968-2975 ◽  
Author(s):  
H.N. Al-Shareef ◽  
A.I. Kingon ◽  
X. Chen ◽  
K.R. Bellur ◽  
O. Auciello
Keyword(s):  
Thin Film ◽  
Electrode Material ◽  
Bottom Electrode ◽  
Low Voltage ◽  
Order Effect ◽  
Major Effect ◽  
Leakage Currents ◽  
Ohmic Behavior ◽  
Thin Film Capacitors ◽  
Pzt Thin Film

Pb(Zr0.53Ti0.47)O3 (PZT) thin film capacitors have been fabricated with four electrode combinations: Pt/PZT/Pt/SiO2Si, RuO2/PZT/Pt/SiO2/Si, RuO2/PZT/RuO2/SiO2/Si, and Pt/PZT/RuO2/SiO2/Si. It is shown that polarization fatigue is determined largely by the electrode type (Pt vs RuO2), and microstructure has only a second-order effect on fatigue. If either the top or bottom electrode is platinum, significant polarization fatigue occurs. Fatigue-free capacitors are obtained only when both electrodes are RuO2. In contrast, the bottom electrode is found to have a major effect on the leakage characteristics of the PZT capacitors, presumably via microstructural modifications. Capacitors with bottom RuO2 electrodes show high leakage currents (J = 10−3-10−5 A/cm2 at 1 V) irrespective of the top electrode material. Capacitors with Pt bottom electrodes have much lower leakage currents (J = 10−8 A/cm2 at 1 V) irrespective of the top electrode material. At low voltage, the I-V curves show ohmic behavior and negligible polarity dependence for all capacitor types. At higher voltages, the leakage current is probably Schottky emission controlled for the capacitors with Pt bottom electrodes.

Preparation of sub-100nm Thickness PZT thin Films with Chemical Solution Deposition Method for low Voltage Operation

2000 ◽  
Vol 655 ◽  
Author(s):  
Yong Kyun Lee ◽  
June Key Lee ◽  
Chang Jung Kim ◽  
Insook Yi ◽  
Ilsub Chung
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Seed Layer ◽  
Low Voltage ◽  
Nucleation Density ◽  
Pzt Thin Films ◽  
Chemical Solution Deposition Method ◽  
Low Voltage Operation ◽  
Pzt Thin Film ◽  
Hysteretic Properties

AbstractPZT thin films with a thickness of 70 nm were successfully fabricated using a modified solution combined with PbTiO3 seed layer. Throughout various approaches, we found that the microstructure of PZT thin film plays an important role in determining the electrical properties such as hysteretic properties and leakage currents, particularly when the thickness is below 100 nm. We modified the precursor system to improve the microstructure in PZT thin film. In addition, we also adopted a thin PbTiO3 seed layer to enhance the initial nucleation density. Finally, we could obtain good electric properties similar to those obtained from 240 nm thick PZT film. The hysteretic properties is excellent enough to operate at a low voltage (2V) for a high density FRAM application.

Effects of PLT-buffer layer on microstructures of sputtered PLZT thin films epitaxially grown on sapphire

1994 ◽  
Vol 9 (11) ◽  
pp. 2959-2967 ◽  
Author(s):  
Kiyotaka Wasa ◽  
Toshifumi Satoh ◽  
Kenji Tabata ◽  
Hideaki Adachi ◽  
Yasumufi Yabuuchi ◽  
...  
Keyword(s):  
Thin Film ◽  
Electron Microscopy ◽  
Thin Films ◽  
Epitaxial Growth ◽  
Buffer Layer ◽  
Sapphire Substrate ◽  
Crystal Orientation ◽  
Interfacial Region ◽  
Plzt Thin Film ◽  
Plzt Thin Films

The microstructures of sputtered thin films of lead-lanthanum zirconate-titanate (PLZT) on (0001) sapphire substrate have been studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Thin films of polycrystalline PLZT (9/65/35), Pb0.91La0.09Zr0.65Ti0.35O3, were prepared on a (0001) sapphire substrate by reactive sputtering, using the dc-magnetron system with a multitarget, Pb, La, Zr, and Ti at the substrate temperature of 700 °C. The PLZT thin films comprised (111) oriented small crystallites of PLZT. Although the average direction of the crystal orientation corresponded to the ideal epitaxial relationship (111) PLZT ‖ (0001) sapphire, the individual crystallites showed misalignment in both the growth direction and the film plane. The thin films could not be considered epitaxially grown films. From analysis of the TEM images, there exists an interfacial region between the PLZT thin film and the substrate. The interfacial region comprises ordered clusters of (111), disordered (101), and/or (110) PLZT crystallites. The presence of the interfacial region will suppress ideal epitaxial growth with uniform crystal orientation. It is confirmed that the addition of the buffer layer of graded composition of PLT-PLZT, between the substrate and the PLZT thin film, will suppress the formation of the disordered interfacial region and will enhance the epitaxial growth of the (111) PLZT on (0001) sapphire with three-dimensional crystal orientations.

Formation of PZT thin-film capacitors over W-plugs and low-voltage operation for high-density LSIs

2000 ◽  
Vol 83 (8) ◽  
pp. 1-7
Author(s):  
Katsuhiro Aoki ◽  
Tomoyuki Sakoda ◽  
Satoshi Hashimoto ◽  
Yukio Fukuda ◽  
Osamu Handa ◽  
...  
Keyword(s):  
Thin Film ◽  
Low Voltage ◽  
High Density ◽  
Low Voltage Operation ◽  
Thin Film Capacitors ◽  
Pzt Thin Film

Correlations Among Degradations in Lead Zirconate Titanate thin Film Capacitors

1993 ◽  
Vol 310 ◽  
Author(s):  
In K. Yoo ◽  
Seshu B. Desu ◽  
Jimmy Xing
Keyword(s):  
Thin Film ◽  
Leakage Current ◽  
Lead Zirconate Titanate ◽  
Oxygen Vacancies ◽  
Lead Zirconate ◽  
Electrical Degradation ◽  
Zirconate Titanate ◽  
Thin Film Capacitors ◽  
Pzt Thin Film ◽  
Degradation Properties

AbstractMany attempts have been made to reduce degradation properties of Lead Zirconate Titanate (PZT) thin film capacitors. Although each degradation property has been studied extensively for the sake of material improvement, it is desired that they be understood in a unified manner in order to reduce degradation properties simultaneously. This can be achieved if a common source(s) of degradations is identified and controlled. In the past it was noticed that oxygen vacancies play a key role in fatigue, leakage current, and electrical degradation/breakdown of PZT films. It is now known that space charges (oxygen vacancies, mainly) affect ageing, too. Therefore, a quantitative ageing mechanism is proposed based on oxygen vacancy migration under internal field generated by either remanent polarization or spontaneous polarization. Fatigue, leakage current, electrical degradation, and polarization reversal mechanisms are correlated with the ageing mechanism in order to establish guidelines for simultaneous degradation control of PZT thin film capacitors. In addition, the current pitfalls in the ferroelectric test circuit is discussed, which may cause false retention, imprint, and ageing.

Characterisation of the fatigued state of ferroelectric PZT thin-film capacitors

1995 ◽  
Vol 29 (1-4) ◽  
pp. 145-148 ◽  
Author(s):  
E.L. Colla ◽  
A.L. Kholkin ◽  
D. Taylor ◽  
A.K. Tagantsev ◽  
K.G. Brooks ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Film Capacitors ◽  
Pzt Thin Film

scholarly journals Thin-film chemical expansion of ceria based solid solutions: laser vibrometry study

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Hendrik Wulfmeier ◽  
Dhyan Kohlmann ◽  
Thomas Defferriere ◽  
Carsten Steiner ◽  
Ralf Moos ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
High Temperature ◽  
Film Thickness ◽  
Solid Solutions ◽  
Low Voltage ◽  
Excitation Frequency ◽  
Dimensional Change ◽  
Potential Core ◽  
Chemical Expansion

Abstract The chemical expansion of Pr0.1Ce0.9O2–δ (PCO) and CeO2–δ thin films is investigated in the temperature range between 600 °C and 800 °C by laser Doppler vibrometry (LDV). It enables non-contact determination of nanometer scale changes in film thickness at high temperatures. The present study is the first systematic and detailed investigation of chemical expansion of doped and undoped ceria thin films at temperatures above 650 °C. The thin films were deposited on yttria stabilized zirconia substrates (YSZ), operated as an electrochemical oxygen pump, to periodically adjust the oxygen activity in the films, leading to reversible expansion and contraction of the film. This further leads to stresses in the underlying YSZ substrates, accompanied by bending of the overall devices. Film thickness changes and sample bending are found to reach up to 10 and several hundred nanometers, respectively, at excitation frequencies from 0.1 to 10 Hz and applied voltages from 0–0.75 V for PCO and 0–1 V for ceria. At low frequencies, equilibrium conditions are approached. As a consequence maximum thin-film expansion of PCO is expected due to full reduction of the Pr ions. The lower detection limit for displacements is found to be in the subnanometer range. At 800 °C and an excitation frequency of 1 Hz, the LDV shows a remarkable resolution of 0.3 nm which allows, for example, the characterization of materials with small levels of expansion, such as undoped ceria at high oxygen partial pressure. As the correlation between film expansion and sample bending is obtained through this study, a dimensional change of a free body consisting of the same material can be calculated using the high resolution characteristics of this system. A minimum detectable dimensional change of 5 pm is estimated even under challenging high-temperature conditions at 800 °C opening up opportunities to investigate electro-chemo-mechanical phenomena heretofore impossible to investigate. The expansion data are correlated with previous results on the oxygen nonstoichiometry of PCO thin films, and a defect model for bulk ceria solid solutions is adopted to calculate the cation and anion radii changes in the constrained films during chemical expansion. The constrained films exhibit anisotropic volume expansion with displacements perpendicular to the substrate plane nearly double that of bulk samples. The PCO films used here generate high total displacements of several 100 nm’s with high reproducibility. Consequently, PCO films are identified to be a potential core component of high-temperature actuators. They benefit not only from high displacements at temperatures where most piezoelectric materials no longer operate while exhibiting, low voltage operation and low energy consumption.

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