J. G. Hong

Electron trapping in noncrystalline remote plasma deposited Hf-aluminate alloys for gate dielectric applications

The physical and electrical properties of noncrystalline Hf-alumiunate alloys, (HfO2)x(Al2O3)1−x, were investigated. Characterization by Auger electron spectroscopy and Fourier transformation infrared spectroscopy confirm these alloys are homogeneous and pseudobinary in character, displaying increased thermal stability against crystallization with respect to the respective end-member oxides. Capacitance–voltage and current density-voltage data as a function of temperature demonstrate that the Hf d states of these alloys act as localized electron traps, and are at an energy approximately equal to the conduction band offset energy of HfO2 with respect to Si. This work also provides additional insight into a previously reported study of Ta-aluminate alloys with localized electron traps associated with d states of the Ta atoms.

Electron traps at interfaces between Si(100) and noncrystalline Al2O3, Ta2O5, and (Ta2O5)x(Al2O3)1−x alloys

The physical and electrical properties of noncrystalline Al2O3, Ta2O5, and their alloys, (Ta2O5)x(Al2O3)1−x, are investigated. Characterization by Auger electron spectroscopy and Fourier transformation infrared spectroscopy confirm these alloys are homogeneous with pseudobinary in character, and display increased thermal stability. Capacitance–voltage and current density–voltage data as a function of temperature demonstrate that the Ta d states of the alloys act as localized electron traps, and are at an energy approximately equal to the conduction band offset of Ta2O5 with respect to Si.

The effect of RuO 2 /Pt hybrid bottom electrode structure on the leakage and fatigue properties of chemical solution derived Pb(Zr x Ti 1− x )O 3 thin films

We have investigated the effect of RuO 2 (10, 30, 50 nm)/Pt layered hybrid bottom electrode structure and film composition on the leakage and fatigue properties of chemical solution derived Pb(Zr x Ti 1− x )O 3 (PZT) thin films. It was observed that the use of high Ti content (Zr: Ti = 30: 70) films with control of excess PbO at the thin RuO 2 (10 nm)/Pt bottom electrode surface reduced leakage current and showed good fatigue properties with high remanent polarization compared to the use of high Zr films (Zr: Ti = 50: 50) or thicker RuO 2 (30, 50 nm)/Pt bottom electrodes. Typical P-E hysteresis behavior of PZT films was observed even at an applied voltage of 3 V, demonstrating greatly improved remanence and coercivity. Fatigue and breakdown characteristics of these modified PZT thin films (Zr: Ti = 30: 70) on RuO 2 (10 nm)/Pt, measured at 5 V, showed stable behavior, and less than 15% fatigue degradation was observed up to 10 10 cycles.

X-ray absorption spectra for transition metal high-κ dielectrics: Final state differences for intra- and inter-atomic transitions

This article applies x-ray absorption spectroscopy to a study of the electronic structure of the high-k gate dielectrics, TiO2, ZrO2, and HfO2. Qualitative and quantitative differences are identified between intra-atomic transitions such as the Zr 3p-state, M2,3 core state absorptions which terminate in TM 4d*- and 5s*-states, and inter-atomic transitions such as the Zr 1s- and O 1s-state K1 absorptions which terminate in Zr 4d*- and 5s*-states that are mixed with O atom 2p* states through nearest neighbor bonding interactions. Differences between the spectral peak energies of the lowest d*-features in the O K1 spectra are demonstrated to scale with optical band gap differences for TiO2, ZrO2, and HfO2, providing important information relevant to applications of TM oxides as high-κ gate dielectrics in advanced Si devices. This is demonstrated through additional scaling relationships between (i) conduction band offset energies between Si and the respective dielectrics, and the optical band gaps, and (ii) t...

Electron trapping in non-crystalline Ta- and Hf-Aluminates for gate dielectric applications in aggressively scaled silicon devices

Abstract The physical and electrical properties of non-crystalline Ta- and Hf-alumiunates, (Ta 2 O 5 ) x (Al 2 O 3 ) 1− x and (HfO 2 ) x (Al 2 O 3 ) 1− x , respectively, were studied. As-deposited films were homogeneous and pseudo-binary in character with increased thermal stability with respect to the respective end-member oxides. Capacitance–voltage and current density–voltage data as a function of temperature demonstrate that the Ta and Hf d-states of the alloys act as localized electron traps, and are at an energy approximately equal to the conduction band offset of Ta 2 O 5 and HfO 2 with respect to Si. This work correlates the studies of Ta- and Hf-aluminates to develop a qualitative conduction band energy level scheme for the two alloys where the interfacial electrical properties are dominated by electron traps of the respective transition metal atoms, and/or or network defects associated with the alloy.

Fixed charge and interface traps at heterovalent interfaces between Si(100) and non-crystalline Al2O3–Ta2O5 alloys

Abstract Characterization by Auger electron spectroscopy, AES, and Fourier transformation infrared spectroscopy, FTIR, confirm that (Ta 2 O 5 ) x (Al 2 O 3 ) 1− x alloys are homogeneous with pseudo-binary in character, and display increased thermal stability. Capacitance–voltage, C–V, and current density–voltage, J–V, data as a function of temperate show that the Ta d-states of the alloys act as localized electron traps, and are at an energy approximately equal to the conduction band offset of Ta 2 O 5 with respect to Si.

INTERFACE ELECTRONIC STRUCTURE OF TA2O5-AL2O3 ALLOYS FOR SI-FIELD-EFFECT TRANSISTOR GATE DIELECTRIC APPLICATIONS

Interfacial electronic structure is important for a fundamental understanding of the properties of field-effect transistor (FET) device structure systems. Previous studies using soft x-ray photoelectron spectroscopy (SXPS) have demonstrated well-defined interface states that appear at binding energies between the peaks due to the substrate Si and the oxide SiO2. Recently we have shown that significant interface changes with annealing for the SiO2/Si system commonly used for FET gate dielectrics illustrating the effectiveness of SXPS for the current study. The present article presents SXPS studies using synchrotron radiation of the electronic structure at the interface between Ta2O5–Al2O3 alloys and Si(111). This system is typical of FET alternative-gate-oxide films and has an electronic structure characteristic of high-k gate dielectrics. Thin films (<20 A) of Ta2O5–Al2O3 alloys were carefully prepared using remote plasma enhanced chemical vapor deposition on Si(111). For this study, SXPS spectra were tak...

The Effect of RuO 2 /Pt Hybrid Bottom Electrode Structure on The Microstructure and Ferroelectric Properties of Sol-Gel Derived PZT Thin Films

Ferroelectric PZT thin films on thin RuO 2 (10, 30, 50nm)/Pt hybrid bottom electrodes were successfully prepared by using a modified chemical solution deposition method. It was observed that the use of a lOnm RuO 2 Pt bottom electrode reduced leakage current, and gave more reliable capacitors with good microstructure compare to the use of thicker RuO 2 /Pt bottom electrodes. Typical P-E hysteresis behavior was observed even at an applied voltage of 3V, demonstrating greatly improved remanence and coercivity. Fatigue and breakdown characteristics, measured at 5V, showed stable behavior, and only below 13-15% degradation was observed up to 10 10 cycles. Thicker RuO 2 layers resulted in high leakage current density due to conducting lead ruthenate or PZT pyrochlore-ruthenate and a rosette-type microstructure.

Structural dependence of breakdown characteristics and electrical degradation in ultrathin RPECVD oxide/nitride gate dielectrics under constant voltage stress

Abstract The structural dependence of breakdown characteristics and electrical degradation in ultrathin oxide/nitride (O/N) dielectrics, prepared by remote plasma enhanced chemical vapor deposition, is investigated under constant voltage stress. In the early stage of oxide wearout, soft breakdown is a local phenomenon dominated by the tunneling current. After a given period of stress, a strong channel-length dependence of dielectric breakdown and the corresponding stress-induced leakage current from the evolution of increased tunneling current have been found. Stacked O/N dielectrics with interface nitridation demonstrate improved device performance on subthreshold swing and threshold voltage shifts after stress, indicating the suppression of stress-induced traps at the oxide/Si and oxide/drain interfaces compared to thermal oxides. Experimental evidence shows more severe breakdown and device degradation in the threshold voltage, drain current and transconductance for shorter channel PMOSFETs with O/N dielectrics. These degradations result from the enhancement of hole trapping in the gate–drain overlap region as evidenced by a positive off-state leakage current, which leads to hard breakdown, and the complete failure of device functionality.

Thermally induced imprint properties of chemical solution derived PLZT thin films

Abstract We investigate the imprint phenomenon by poling ferroelectric PLZT capacitors into a known state and exposing the devices to elevated temperatures. It is found that the compensation of oxygen vacancies is a important process parameter in determining the tendency to imprint. In the case of PLZT thin films, the voltage shifts related to imprint failure are attributed to the trapping electrons at defect sites near film/electrode interface, the magnitude of polarization and concentration of defect-dipole complexes involving oxygen vacancies such as V″Pb - V″o. The thermally induced voltage shifts in PLZT thin films are dopant concentration dependent and decrease with increasing the La concentration of the films.