Y. Y. Lin

Enhancement of endurance for Cu x O based RRAM cell

For the first time, we report that the copper oxide (CuxO) based resistive random access memory (RRAM) cell can achieve 104 cycles (i.e. ~10x better) as a new record as well as elimination of the initial ¿forming¿ than reported in literature. The copper oxide is integrated in MIM (metal-insulator-metal) structure and is grown by plasma oxidation of Cu substrate, with CuO near upper surface and graded CuxO (i.e. increasingly Cu rich or O-vacancies rich) toward the Cu substrate. A thinner CuO upper layer can eliminate ¿forming¿ process and, for in turn, greatly enhance the endurance of resistive switching by eliminating the damage during the ¿forming¿ process.

Improvement of Resistive Switching in

Wide dispersions of memory switching parameters are observed in resistive random access memory based on Al/CuxO/Cu structure. Moreover, the switching instability induced by these dispersions is studied. In this letter, a ramped-pulse series operation method is put forward, which can improve switching stability and cycling endurance remarkably. A method for minimizing the dispersion of Vreset by optimizing the amplitude of pulse is proposed further. The write-read-erase-read operations can be over 8 times103 cycles without degradation by using the new operation mode. The role of Joule heating behind this behavior of Al/CuxO/Cu device is discussed.

\hbox{Cu}_{x} \hbox{O}

Bimorph-type bending actuators have been widely used in many applications as converters of electric input to mechanical motion, or vice versa. In this paper a new piezoelectric model of a multilayer piezoelectric cantilever is obtained, and the analytic expressions for the curvature, displacement and tip-deflection of the multilayer structure are derived in the static state. With the use of this model and the solution, the tip-deflections of the piezoelectric bimorph cantilever in different working situations are compared and the effect of the metal electrodes on the tip-deflection of the cantilever is considered. The above-mentioned methods and conclusions can be used for optimized design of PZT cantilever structure.

Using New RESET Mode

The determination of the coercive voltage from the height of domain-switching current plateau in ferroelectric thin films provides the liability to estimate the coercive-voltage shift with imprint time shortly on the order of polarization-reversal time. The voltage shift exhibits a linear time dependence in a logarithmic scale above an initial time (∼1μs), below which the voltage is nearly constant. The modeling of imprint on the basis of the interfacial charge injection at different stressing voltages strongly supports Schottky emission as a dominant mechanism, instead of Frenkel-Poole emission and Fowler-Nordheim tunneling.

Study on the tip-deflection of a piezoelectric bimorph cantilever in the static state

The complex impedance spectroscopy method associated with capacitance-voltage is employed to investigate the resistive switching behavior of the bilayer structure for the first time. The reset current is reduced by more than one order for the AlOx/WOx bilayer compared with that of the single-layer structure. It is distinguished that each layer plays an important role. The AlOx layer is the dominating switching layer, while the WOx layer has the functions of controlling the conductive filaments in the AlOx layer and acting as a series impedance to reduce the reset current.

Nanosecond-range measurements of imprint effect for Pt∕IrO2∕Pb(Zr0.4Ti0.6)O3∕IrO2∕Pt thin-film capacitors

The relationship between low resistance (<i>R</i>_on) and cell size (from 40 nm to 100 μm) is systematically investigated using a 1-Mb Cu<i>x</i>Si<i>y</i>O resistive RAM (RRAM) array. To our knowledge, this is the first study to attempt such an endeavor. Spacer pattern technology is employed to obtain a small cell size on the basis of a 0.13-μm standard logic process. <i>R</i>_on exhibits minimal change at 100 μm to 90 nm of RRAM size. However, it quadratically increases at 90 to 40 nm. The reset current, which is highly dependent on <i>R</i>_on, is linearly reduced fivefold in accordance with cell size, thereby improving overall power reduction and cell size scaling. The <i>R</i>_on dependence on cell size can be well explained by the dendritelike conductive filament model.

Low Reset Current in Stacked

The time interval for the completion of slow polarization reversal in ferroelectric thin films measured in the order of magnitude of 10−9–100s is broadened by more than two decades as the applied field approaches the coercive field of domain switching. The domain-switching kinetics is conjectured to change from the classical Kolmogorov–Avrami–Ishibashi (KAI) model at high fields to nucleation-limited-switching (NLS) model at low fields. However, the true voltage drop across the film from the real-time measurement of the oscilloscope remains constant at a coercive voltage Vc during polarization reversal irrespective of the applied voltage. Therefore, the above high-field assumption for KAI does not exist. From our measurements, a long-time effect of imprint can occur for any slow processes of physical phenomena, even if the imprint field is very weak. The imprinted Vc can be estimated either from the voltage shift in the curve of switched polarization versus the applied voltage or directly from the height ...

\hbox{AlO}_{x}/ \hbox{WO}_{x}

A new conception on non-volatile ferroelectric FPGA (NVFeFPGA) was proposed in this paper, which is based on FeRAM-Programming, instead of SRAM. Two different nonvolatile configuration storage cells are put forward, according to configuration the logic elements and the routing switches respectively. And three main elements of FPGA are also constructed and considered for nonvolatility.

Resistive Switching Memory

ABSTRACT Ferroelectric xBiFeO3-(1-x) Sr0.8Bi2.2Ta2O9 [xBFO-(1-x)SBT] solid solution with x ranging from 0 to 0.4 was synthesized on Pt/Ti/SiO2/Si by metalorganic decomposition method. This solid solution system has been found to have a layered perovskite structure and good ferroelectric properties. The remnant polarizations (2Pr) are 9.1 μ C/cm2 and 7.9 μ C/cm2, while coercive field (2Ec) are 196 kV/cm and 209 kV/cm, respectively for 0.2BFO-0.8SBT and 0.4BFO-0.6SBT at an applied field of 300 kv/cm. It is found that increase of BFO concentration decreases the remnant polarization and the dielectric constant, increases the coercive field and the leakage current at certain applied voltage. The highest loss of tangent is observed for 0.8SBT-0.2BFO. It is found that the fatigue properties are decreased when more BFO was added to SBT films. The results were discussed with respect to the effects of Bi3+ and Fe3+ in BFO substitution at layered perovskite A and B site of SBT.

Linear Scaling of Reset Current Down to 22-nm Node for a Novel

Novel multilevel non-destructive-read-out FFRAM is proposed in this paper, in which data more than one bit can be stored in a metal-ferroelectric-insulator-semiconductor field-effect transistor (MFISFET) memory cell to increase bit-area property. Given the same storage capacity, the number of cells in multilevel FFRAM decreases significantly compared with current FFRAM, thus chip area and power consumption are reduced accordingly. An original multilevel NDRO FFRAM cell is proposed, in which multi-bit binary data can be stored into a selected cell of the memory array and be read out correctly. A HSPICE macro model of metal-ferroelectric-insulator-semiconductor field-effect transistors (MFISFETs) using cascade Schmitt trigger model is created for simulating saturated and unsaturated hysteresis loops. Realization of a multilevel NDRO FFRAM cell and the structure of the memory array are discussed. The timing sequence of the “write”, “read” as well as “clear” operation is also investigated. A 4× 4 memory array with A/D converters as I/O is presented in the end.