Sanghun Jeon

Effect of hygroscopic nature on the electrical characteristics of lanthanide oxides (Pr2O3, Sm2O3, Gd2O3, and Dy2O3)

The hygroscopic nature of lanthanide oxides such as Pr2O3, Sm2O3, Gd2O3, and Dy2O3 was characterized by means of x-ray photoelectron spectroscopy and its effect on the electrical characteristics of the compounds was investigated. Among the four samples, Pr2O3 was found to be the most reactive with water which can be attributed to the relatively large ionic radius and lower electronegativity of Pr. In contrast, Dy2O3 was the least reactive with water. A direct correlation between the hygroscopicity and electronegativity of lanthanide elements was found. With increasing hygroscopicity, a significant growth of interfacial oxide with annealing temperature was observed. A clear understanding of the nature of hygroscopic effects and the optimization of process flow will be needed for future high-k gate dielectric application.

Electrical characteristics of ZrOxNy prepared by NH3 annealing of ZrO2

The electrical characteristics of ZrOxNy prepared by NH3 annealing of ZrO2 were investigated for use in metal–oxide–semiconductor gate dielectric applications. Compared with conventional ZrO2, ZrOxNy exhibits excellent electrical characteristics such as high accumulation capacitance, low leakage current density, and superior thermal stability. Based on high resolution transmission electron microscope analysis of both ZrO2 and ZrOxNy samples which had been annealed at 800 °C for 5 min, the ZrO2 exhibited a polycrystalline state but the ZrOxNy was amorphous in structure. In addition, the thickness of ZrOxNy was thinner than that of ZrO2. The improvement in electrical characteristics can be explained by the better thermal stability and lower rate of oxidation of ZrOxNy.

Electrical and physical characteristics of PrTixOy for metal-oxide-semiconductor gate dielectric applications

The electrical and physical characteristics of PrTixOy, for use in metal-oxide-semiconductor gate dielectric applications were investigated. An amorphous layer of PrTixOy with an equivalent oxide thickness of 1 nm and a dielectric constant of 23 was formed by means of e-beam evaporation. Compared to Pr2O3, PrTixOy was found to exhibit excellent characteristics such as a high accumulation capacitance, a low leakage current density, a thin interfacial layer, and a lower reactivity to water. The superiority of PrTixOy can be attributed to the addition of TiO2 to the praseodymium oxide matrix.

Excellent thermal stability of Al2O3/ZrO2/Al2O3 stack structure for metal–oxide–semiconductor gate dielectrics application

The thermal stability of a nanolaminate (Al2O3/ZrO2/Al2O3) gate stack prepared by atomic layer chemical vapor deposition was investigated using medium-energy ion scattering spectroscopy, and x-ray photoelectron spectroscopy. We observed that the structure was stable up to 1000 °C under ultrahigh vacuum conditions. However, annealing in a nitrogen or oxygen ambient at 1 atm yielded the formation of an interfacial Zr–Al silicate layer at much lower temperatures. The growth of the interfacial silicate layer could be significantly reduced during furnace annealing via the use of plasma nitridation.

Size-dependent charge storage in amorphous silicon quantum dots embedded in silicon nitride

Size-dependent charge storage was observed in metal–insulator–semiconductor structures containing amorphous Si quantum dots (a-Si QDs) grown by plasma-enhanced chemical vapor deposition. For a-Si QDs as large as 2 nm in diameter, one electron or one hole was stored in each a-Si QD. For small-sized a-Si QDs of 1.4 nm in diameter, however, the width of capacitance–voltage hysteresis was decreased, indicating that the charge density in the a-Si QDs was reduced. This can be attributed to the lowered tunneling barrier in the small-sized a-Si QDs resulting from a large quantum confinement effect. Long-term charge storage was observed in the fully charged a-Si QDs; this is attributed to a suppression of the discharge process by electrostatic repulsion among the charged dots.

Resistive Switching Characteristics of Solution-Processed Transparent TiO x for Nonvolatile Memory Application

We propose a solution-processed transparent TiO x -based resistive switching random access memory (ReRAM) device. Electronically active TiO x was prepared by sol-gel spin coating of a titanium(IV) isopropoxide precursor on an indium tin oxide-coated glass. The prepared TiO x film is completely transparent in the visible range and has an amorphous structure. The fabricated TiO x -based ReRAM device exhibits distinct resistive switching under consecutive dc voltage sweeps of ±2 V. The device also exhibits good memory performance, including fast switching speed with a pulse width of 1 μs, stable pulse endurance over 1000 cycles, and excellent retention characteristics at up to 125 °C. In addition, based on the log I - log V plot and X-ray photoelectron spectroscopy analysis, we postulate that the fabricated device is operated by the reversible formation/rupture of the conducting filament in the oxygen-deficient TiO x layer.

Electrical characteristics of epitaxially grown SrTiO 3 on silicon for metal-insulator-semiconductor gate dielectric applications

We have found excellent electrical characteristics of epitaxially grown SrTiO/sub 3/ by molecular beam epitaxy (MBE) for silicon metal-insulator-semiconductor (MIS) gate dielectric application. For thin SrTiO/sub 3/ film, the equivalent oxide thickness (EOT) and leakage current density was 5.4 /spl Aring/ and 7 /spl times/ 10/sup -4/ A/cm/sup 2/ (@V/sub g/ = V/sub fb/ - 1 V), respectively. In addition, the dispersion and hysteresis characteristics were negligible. As-deposited samples show relatively high fixed oxide charge density and interface state density, but both of these characteristics are substantially reduced by an optimizing low temperature (< 450 /spl deg/C) post-metal forming gas anneal (FGA).

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.

Electrical characteristics of a Dy-doped HfO2 gate dielectric

This letter describes a process for the preparation of high-quality Dy-doped HfO2 for use in gate dielectric applications. Compared with conventional undoped HfO2, the HfO2 gate dielectric which contains an optimum concentration of Dy exhibits the lowest leakage current and minimum effective oxide thickness. The lower electronegativity and larger atomic radii of Dy contribute to the improvement in leakage current for Dy-doped HfO2. The Dy-doped HfO2 is a promising gate dielectric layer for use in future high-k gate dielectric applications.

Electrical and structural properties of nanolaminate (Al2O3/ZrO2/Al2O3) for metal oxide semiconductor gate dielectric applications

We investigated electrical and material properties of an untrathin nanolaminate (Al2O3/ZrO2/Al2O3) structure, prepared by atomic-layer chemical vapor deposition (ALCVD), for use in metal-oxide-semiconductor gate dielectric applications. The properties of nanolaminate were characterized by various technique such as high-resolution transmission electron microscopy (HRTEM), medium-energy ion scattering (MEIS), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and electrical analysis of MOS capacitors. Compared with the roughness of ZrO2 on bare silicon, ZrO2 on Al2O3 shows negligible roughness confirmed by AFM and HRTEM. Excellent electrical characteristics such as an equivalent oxide thickness (EOT) of 10.2 A and a leakage current density of 3×10-4 A/cm2 were obtained at 1 V below the flatband voltage. The conduction mechanism of nanolaminate can be explained by trap-assisted tunneling through ZrO2 and direct tunneling through Al2O3.