Hyunjun Sim

Reversible resistive switching of SrTiOx thin films for nonvolatile memory applications

Nonvolatile and reversible bistable and multistable resistance states of polycrystalline SrTiOx thin film were studied. The pulse-laser-deposition method was employed to grow the film, and the clear resistance switching was observed under dc bias sweep and voltage pulses. More than two controllable resistance states were observed by applying voltage pulses. These reversible states have a resistance difference by nearly two orders of magnitude, and we verified that this sharp resistance switching takes place at the metal-oxide interface. Excellent reliability characteristics, such as endurance cycles of up to 105 times and data retention time of up to 106s at 125°C demonstrate the promise of SrTiOx film for future nonvolatile random access memory applications.

Resistance switching of the nonstoichiometric zirconium oxide for nonvolatile memory applications

The resistance switching behavior and switching mechanism of nonstoichiometric zirconium oxide thin films were investigated for nonvolatile memory application. The Pt/ZrO/sub x//p/sup +/-Si sandwich structure fabricated by reactive sputtering shows two stable resistance states. By applying proper bias, resistance switching from one to another state can be obtained. The composition in ZrO/sub x/ thin films were confirmed from X-ray photoelectron spectroscope (XPS) analysis, which showed three layers such as top stoichiometric ZrO/sub 2/ layer with high resistance, transition region with medium resistance, and conducting ZrO/sub x/ bulk layer. The resistance switching can be explained by electron trapping and detrapping of excess Zr/sup +/ ions in transition layer which control the distribution of electric field inside the oxide, and, hence the current flow.

Resistance-switching Characteristics of polycrystalline Nb/sub 2/O/sub 5/ for nonvolatile memory application

The resistance switching characteristics of polycrystalline Nb/sub 2/O/sub 5/ film prepared by pulsed-laser deposition (PLD) were investigated for nonvolatile memory application. Reversible resistance-switching behavior from a high resistance state to a lower state was observed by voltage stress with current compliance. The reproducible resistance-switching cycles were observed and the resistance ratio was as high as 50-100 times. The resistance switching was observed under voltage pulse as short as 10 ns. The estimated retention lifetime at 85/spl deg/C was sufficiently longer than ten years. Considering its excellent electrical and reliability characteristics, Nb/sub 2/O/sub 5/ shows strong promise for future nonvolatile memory applications.

Excellent resistance switching characteristics of Pt/SrTiO/sub 3/ schottky junction for multi-bit nonvolatile memory application

We have investigated single crystal Nb-doped SrTiO₃ in terms of its potential utility in nonvolatile memory applications. Compared with polycrystalline oxide (Nb₂O₅, ZrO _x and Cr-SrTiO₃), the Pt/single crystal Nb:SrTiO ₃ Schottky junction exhibits excellent memory characteristics including uniformity of set/reset bias, die-to-die reproducibility, data retention at high temperature, reliability under cycle stress, and multi-bit operation characteristics. The switching mechanism might be explained by modulation of the Schottky barrier height by charge trapping at the interface

Excellent electrical characteristics of lanthanide (Pr, Nd, Sm, Gd, and Dy) oxide and lanthanide-doped oxide for MOS gate dielectric applications

In this paper, we report on an investigation of the electrical characteristics of various amorphous lanthanide oxides prepared by e-beam evaporation. Excellent electrical characteristics were found for the amorphous lanthanide oxide including a high oxide capacitance, low leakage current, and high thermal stability. We also confirmed the excellent thermal stability and mobility characteristics of lanthanide silicate (PrSi/sub x/O/sub y/). In addition, lanthanide-doped HfO/sub 2/ also exhibited a significant reduction in leakage current at the same equivalent oxide thickness.

Effect of deuterium postmetal annealing on the reliability characteristics of an atomic-layer-deposited HfO2/SiO2 stack gate dielectrics

The characteristics of atomic-layer-deposited (ALD) HfO2(30 A)/SiO2(10 A) stacks gate dielectrics were investigated after annealing in a deuterium (D2) ambient. Compared with oxides annealed in a forming gas containing hydrogen (H2), the stack dielectrics annealed in D2 ambient exhibited various advantages such as less charge trapping, less generation of interface state density (Dit), a larger charge-to-breakdown (Qbd), and longer time-dependent dielectric breakdown characteristics under conditions of electrical stress. The improved reliability can be attributed to the strength of the deuterium bond. This deuterium postmetal annealing of a high-k gate dielectric has considerable potential for future use in ultralarge-scale integration device applications.

Excellent Resistance Switching Characteristics of Pt/Single-crystal Nb-Doped SrTiO3 Schottky Junction

The hysteretic resistance switching characteristics of Pt/Nb-doped STO Schottky junctions were investigated for nonvolatile memory applications. The Pt/single crystal Nb:STO Schottky junction exhibits excellent resistance switching characteristics such as stable pulse switching, uniform set/rest state and die-to-die uniformity. The switching mechanism might be explained by modulation of the Schottky tunnel barrier width by charging and discharging of electron in oxygen vacancy

Electrical and Structural Characteristics of High-k Gate Dielectrics with Epitaxial Si3N4 Interfacial Layer on Si(111)

In this study, the electrical and structural characteristics of Gd2O3 gate dielectrics with an epitaxial Si3N4 interfacial layer grown on Si(111) were investigated. Compared with control Gd2O3 gate dielectrics deposited on HF-last treated Si (111), the Gd2O3 gate dielectrics with an epitaxial Si3N4 interfacial layer exhibited excellent electrical characteristics such as low leakage current density and low interface state density. These characteristics are due to a high-quality interfacial layer formation on Si. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy were employed to analyze the structures of the gate dielectrics and interfacial layer. High-k gate dielectrics with an epitaxial Si3N4 interfacial layer have considerable potential for future use in sub-0.1 µm metal oxide semiconductor field-effect transistors (MOSFETs).

Electrical Characteristics of Ozone-Oxidized HfO2 Gate Dielectrics.

Electrical and reliability characteristics of HfO2 gate dielectrics prepared by low-temperature ozone (O3) oxidation of ultra thin Hf metal were investigated. Compared with control HfO2 annealed in O2 ambient, HfO2 annealed in O3 ambient exhibited excellent characteristics such as lower leakage current density, lower hysteresis, lower frequency dispersion, lower degree of charge trapping (ΔVg), and larger charge to breakdown (Qbd) under electrical stress. The improved electrical and reliability characteristics can be attributed to the lower density of charge trap sites which are related to nonstoichiometry and oxygen vacancy. HfO2 prepared by O3 oxidation is a promising alternative gate dielectric for future metal–oxide–semiconductor (MOS) device applications.

The HfSi x O y Interfacial Layer Effect on Improving Electrical Characteristics of Ultrathin High-κ TiO2 Gate Dielectric

We report significant improvement of the electrical characteristics of high-quality titanium oxide (TiO 2 ) with hafnium silicate (HfSi x O y ) as an interfacial layer as the gate dielectrics in a metal oxide semiconductor (MOS) structure. Compared with conventional chemical oxide and oxynitride as interfacial layers, TiO 2 /HfSi x O y exhibited excellent electrical characteristics such as a lower leakage current density of 3 × 10 - 5 A/cm 2 at a gate bias of -1 V below flatband voltage under an equivalent oxide thickness of 10.8 A and low interface trap sites monitored by the conductance loss peak characteristics. Based on its excellent electrical characteristics, TiO 2 /HfSi x O y is a promising alternative gate dielectric for future MOS field effect transistor device applications.