Recent Progress in Ferroelectric Random Access Memory Technology

2007 ◽  
Vol 997 ◽  
Author(s):  
Hiroshi Ishiwara ◽  
Hiroshi Ishiwara
Keyword(s):  
Electric Field ◽  
Leakage Current ◽  
Retention Time ◽  
Cell Structure ◽  
Random Access ◽  
Hysteresis Loops ◽  
Ferroelectric Materials ◽  
Buffer Layers ◽  
Data Retention ◽  
Gate Structure

AbstractIn this paper, ferroelectric materials suitable for realizing high-density 1T1C-type (capacitor-type) FeRAM are first reviewed. It is found in BiFeO3(BFO) films formed by chemical solution deposition that leakage current density at a low electric field increases by substitution of Mn and Cr atoms for Fe atoms. But, it is also found that the breakdown characteristic is much improved by substitution of these atoms. Because of the better breakdown characteristic, the leakage current densities in the 3 and 5% Mn-substituted films are lower than that in an undoped BFO film at an applied electric field of 1MV/cm at room temperature, and thus well saturated hysteresis loops in P-E (polarization vs. electric field) characteristics are observed in these films.Next, recent technological progress in transistor-type FeRAM, in which data are stored in a single ferroelectric-gate FET(field effect transistor), is discussed. It is demonstrated that the data retention time of ferroelectric-gate FETs is much improved by use of HfO2-based buffer layers which are inserted between the ferroelectric film and Si substrate for preventing interdiffusion of constituent elements. Particular attention is paid to FETs with a Pt/SrBi2Ta2O9/HfO2/Si gate structure, in which the data retention time longer than 30 days has been attained. Finally, the cell structure and operation principle of 1T (one transistor)-type FeRAM are discussed.

High-κ Insulator Thin Films and Retention Properties of MFIS Diodes

2011 ◽  
Vol 1345 ◽  
Author(s):  
Yichun Zhou
Keyword(s):  
Thin Films ◽  
Leakage Current ◽  
High Speed ◽  
Random Access ◽  
Ferroelectric Thin Film ◽  
Buffer Layers ◽  
Interface Properties ◽  
Si Substrate ◽  
Device Structure ◽  
Low Leakage

ABSTRACTFerroelectric field effect transistor (FFET) is a promising candidate for non-volatile random access memory because of its high speed, single device structure, low power consumption, and nondestructive read-out operation. Currently, however, such ideal devices are commercially not available due to poor interface properties between ferroelectric film and Si substrate, such as leakage current and interdiffusion etc. So we choose YSZ and HfO2 insulating thin films as buffer layer due to they possess relatively high dielectric constant, high thermal stability, low leakage current, and good interface property with Si substrates. Two structural diodes of Pt/BNT/YSZ/Si and Pt/SBT/HfO2/Si were fabricated, and the microstructures, interface properties, C-V, I-V, and retention properties were investigated in detail. Experimental results show that the fabricated diodes exhibit excellent long-term retention properties, which is due to the good interface and the low leakage density, demonstrating that the YSZ and HfO2 buffer layers are playing a critical modulation role between the ferroelectric thin film and Si substrate.

Investigation of Retention Properties for YMnO3 Based Metal/Ferroelectric/Insulator/Semiconductor Capacitors

2003 ◽  
Vol 784 ◽  
Author(s):  
T. Yoshimura ◽  
D. Ito ◽  
H. Sakata ◽  
N. Shigemitsu ◽  
K. Haratake ◽  
...  
Keyword(s):  
Electric Field ◽  
Leakage Current ◽  
Electric Fields ◽  
Retention Time ◽  
Memory Retention ◽  
Frenkel Emission ◽  
Transient Spectroscopy ◽  
Leakage Current Mechanism ◽  
Capacitance Transient ◽  
The Relationship

ABSTRACTThe memory retention properties of Pt/YMnO3/Y2O3/Si capacitors were investigated for the application of ferroelectric gate transistors. The epitaxially grown Pt/YMnO3/Y2O3/Si capacitors showed ferroelectric type hysteresis loop on the capacitance-voltage properties. Although the retention time of the as-deposited capacitors was ∼103 s, it was prolonged up to 104 s when the leakage current density was reduced from 4×10-8 A/cm2 to 2×10-9 A/cm2 by the annealing under N2 ambience. To reveal the relationship between the retention time and leakage current, the leakage current mechanism was investigated comparing several conduction mechanisms. It was found that the dominant leakage mechanisms at high and low electric fields were Poole-Frenkel emission from the Y2O3 layer and ohmic conduction, respectively. This result indicates that the leakage current was limited by the Y2O3 layer at high electric field and was mainly dominated by the amount of defects in the YMnO3 layer at low electric field. From the pseudo isothermal capacitance transient spectroscopy (ICTS), it was determined that the trap density was in an order of 1015 cm-3. Since the variation of the leakage current by annealing was observed only in the low electric field region, it is suggested that the retention properties of the Pt/YMnO3/Y2O3/Si capacitors was influenced by the amount of defects in the YMnO3 layer.

scholarly journals Investigation of the dielectric fatigue on the example of lead titanate films PbTiO3

2021 ◽  
Vol 2086 (1) ◽  
pp. 012179
Author(s):  
A V Fimin ◽  
E A Pecherskaya ◽  
O A Timokhina ◽  
V S Aleksandrov ◽  
A V Volik ◽  
...  
Keyword(s):  
Thin Films ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Lead Titanate ◽  
Piecewise Linear ◽  
Hysteresis Loops ◽  
Ferroelectric Materials ◽  
Piecewise Linear Approximation ◽  
Residual Polarization

Abstract The phenomenon of dielectric fatigue of active dielectrics, which consists in a decrease in the residual polarization depending on the number of switching cycles, is researched. A model of the dependence of the residual polarization of ferroelectric materials on the number of switching cycles is proposed. The model is based on piecewise - linear approximation of the results of measurements of the hysteresis loops of thin films PbTiO3 at a temperature T = 470 (°C), the electric field strength E = 100 (kV/cm). The developed model was used in the development of a technique for studying dielectric fatigue, depending on different modes of material switching.

Study of Retention Time Variation due to the Change in Adjacent Wordline Voltage of BCAT DRAM Structure

2020 ◽  
Author(s):  
Dongsuck Kang ◽  
Ilwoo Jung ◽  
Jinsuob Yoon ◽  
Dongin Lee ◽  
Hyeongsun Hong ◽  
...  
Keyword(s):  
Electric Field ◽  
Leakage Current ◽  
Electrostatic Potential ◽  
Retention Time ◽  
Time Variation ◽  
Design Rule ◽  
Adjacent Line ◽  
New Perspective

Abstract As DRAM design rule (D/R) shrinks, the retention time due to leakage current becomes more important. Retention time failures that arise from gate induced drain leakage (GIDL) or junction leakage are exacerbated by changes in the electrostatic potential between adjacent lines or nodes. This study analyzes the effects of wordline (adjacent line) potential on retention time based on in sub-20nm DRAM technology. Electrical tests have confirmed that cells that fail from GIDL and junction leakage exhibit different behaviors according to the leakage characteristic and changes in adjacent wordline (especially in word-line across STI) potential. Simulations also confirm that these observations are due to the change in electric field. Based on these findings, a new perspective on the mechanism of retention failures is proposed.

Investigation of Retention Properties for YMnO3 Based Metal/Ferroelectric/Insulator/Semiconductor Capacitors

2003 ◽  
Vol 786 ◽  
Author(s):  
T. Yoshimura ◽  
D. Ito ◽  
H. Sakata ◽  
N. Shigemitsu ◽  
K. Haratake ◽  
...  
Keyword(s):  
Electric Field ◽  
Leakage Current ◽  
Electric Fields ◽  
Retention Time ◽  
Memory Retention ◽  
Frenkel Emission ◽  
Transient Spectroscopy ◽  
Leakage Current Mechanism ◽  
Capacitance Transient ◽  
The Relationship

ABSTRACTThe memory retention properties of Pt/YMnO3/Y2O3/Si capacitors were investigated for the application of ferroelectric gate transistors. The epitaxially grown Pt/YMnO3/Y2O3/Si capacitors showed ferroelectric type hysteresis loop on the capacitance-voltage properties. Although the retention time of the as-deposited capacitors was ∼103 s, it was prolonged up to 104 s when the leakage current density was reduced from 4×10−8 A/cm2 to 2×10−9 A/cm2 by the annealing under N2 ambience. To reveal the relationship between the retention time and leakage current, the leakage current mechanism was investigated comparing several conduction mechanisms. It was found that the dominant leakage mechanisms at high and low electric fields were Poole-Frenkel emission from the Y2O3 layer and ohmic conduction, respectively. This result indicates that the leakage current was limited by the Y2O3 layer at high electric field and was mainly dominated by the amount of defects in the YMnO3 layer at low electric field. From the pseudo isothermal capacitance transient spectroscopy (ICTS), it was determined that the trap density was in an order of 1015 cm−3. Since the variation of the leakage current by annealing was observed only in the low electric field region, it is suggested that the retention properties of the Pt/YMnO3/Y2O3/Si capacitors was influenced by the amount of defects in the YMnO3 layer.

Hysteretic Dynamics of Ferroelectric Materials Under Electro-Mechanical Loadings

2008 ◽  
Author(s):  
Linxiang Wang
Keyword(s):  
Electric Field ◽  
Phase Transformations ◽  
Landau Theory ◽  
Hysteresis Loops ◽  
Ferroelectric Materials ◽  
Differential Model ◽  
Mechanical Coupling ◽  
First Order ◽  
Bias Stress ◽  
First Order Phase

In the current paper, the hysteretic dynamics of ferroelectric materials under combined electro-mechanical loadings is investigated using a macroscopic differential model. The model is constructed on the basis of the Landau theory of the first order phase transformations. Hysteresis loops in the electric field and the butterfly-shaped behaviors in the electro-mechanical coupling are modeled as a consequence of polarizations and orientation switchings, together with nonlinear electro-mechanical coupling effects. The effects of bias stress on the orientation switchings are investigated numerically. Comparison of the model results with its experimental counterparts is presented, capability of the model is approved.

Non-Volatile Memory Behaviour of MFIS Structure with Ba0.7Sr0.3TiO3 Films for Memory Capacitor Application

2012 ◽  
Vol 557-559 ◽  
pp. 1861-1864 ◽  
Author(s):  
Htet Htet Nwe ◽  
Yin Maung Maung ◽  
Than Than Win ◽  
Ko Ko Kyaw Soe
Keyword(s):  
Electric Field ◽  
Remanent Polarization ◽  
Random Access ◽  
Hysteresis Loops ◽  
Microstructural Characterization ◽  
Access Memory ◽  
Impedance Analyzer ◽  
Non Volatile Memory ◽  
Polarization Electric Field ◽  
Lcr Meter

The growth of strontium doped barium titanate (BST) powder is performed by solid-state reaction. Microstructural characterization by SEM technique confirms the BST film is successfully formed on p-Si (100) substrate by spin coating technique. Dielectric properties of MFIS (Metal/ Ferroelectric/ Insulator/ Semiconductor) designs are measured by impedance analyzer (LCR meter, QuadTech :1730). P-E (polarization-electric field) hysteresis loops are also measured by applying the same triangular wave electric field in order to allow their application in NVFeRAM (Non-Volatile Ferroelectric Random Access Memory). The maximum remanent polarization density (Pr=38.6µC/cm2) is found at BST film 600°C. The film exhibits the potential to be a future promising memory. The results obtained from this research are quite interesting, acceptable, credible and applicable in use for NVFeRAM.

New Line of Solid Solution System of Oxide Ferroelectrics

2002 ◽  
Vol 748 ◽  
Author(s):  
Takeshi Kijima ◽  
Hiroshi Ishiwara
Keyword(s):  
Leakage Current ◽  
Solid Solutions ◽  
Random Access ◽  
Ferroelectric Materials ◽  
Cross Sectional ◽  
Pronounced Increase ◽  
Transmission Electron ◽  
Saturation Polarization ◽  
High Pressure Oxygen ◽  
Current Characteristics

ABSTRACTFerroelectric random access memory is one of the most promising candidates of non-volatile memories and has already been commercialized. However there still exist some problems to be solved on the ferroelectric materials. We succeeded in solving these problems by forming solid solutions between Bi2SiO5 and conventional ferroelectric materials such as Bi4Ti3O12, SrBi2Ta2O9 and Pb(Zr,Ti)O3. It was found that Bi2SiO5 enhanced crystallization of the ferroelectric materials and finally formed solid solutions with them. As a result, the crystallization temperature of the films decreased by 150 to 200 °C, and the ferroelectric and leakage current characteristics did not degrade even in an ultra-thin film of 13 nm in thickness. On the other hand, it was also found that the ferroelectric and insulating characteristics of the BSO-added films were dramatically improved by annealing in high-pressure oxygen up to 9.9 atms.[1] Three-orders-of-magnitude improvement of the leakage current density was observed in BSO-added BLT films after annealing at 9.9 atms, while pronounced increase of the saturation polarization was observed in BSO-added SBT and PZT films. From cross-sectional TEM (Transmission electron microscopy) observation, origin of the improved characteristics was speculated to be the structural change of the films.[2]

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