Ingram Yin-Ku Chang

Metal-ferroelectric (BiFeO3)-insulator (Y2O3)-semiconductor capacitors and field effect transistors for nonvolatile memory applications

Metal-ferroelectric-insulator-semiconductor capacitors and field effect transistors with Al/BiFeO3/Y2O3/Si structure were fabricated and characterized for nonvolatile memory applications. The capacitance-voltage curves exhibit a maximum clockwise memory window of 0.92 V. The minimum leakage current density is 2×10−7 A/cm2 at an applied voltage of 5 V. The capacitance-voltage memory window as a function of the sweep voltage range was investigated. The IDS-VGS curves of metal-ferroelectric-insulator-semiconductor transistors show a maximum memory window of 0.84 V. The drain current on/off ratio maintained more than three orders of magnitude after an elapsed time of 104 s.

Electrical characterization of CeO2∕Si interface properties of metal-oxide-semiconductor field-effect transistors with CeO2 gate dielectric

Metal-oxide-semiconductor field-effect transistors with CeO2 gate dielectrics were fabricated. The lowest interface trap density (Dit) of CeO2∕Si interface in comparison with other high-κ gated diodes is 1.47×1012cm−2eV−1 due to the very low lattice mismatch of CeO2∕Si. The interfacial properties were characterized by gated-diode measurements. The surface recombination velocity (s0) and the minority carrier lifetime in the field-induced depletion region (τ0,FIJ) measured from the gated diodes are about 1.03×104cm∕s and 2.73×10−8s, respectively. The effective capture cross section of surface state (σs) extracted using the gated diode technique and the subthreshold swing measurement is about 8.68×10−15cm2.

Temperature dependence of the current conduction mechanisms in LaAlO3 thin films

Metal-oxide-semiconductor capacitors and transistors with LaAlO3 dielectric films were fabricated and the current conduction mechanisms were studied. The LaAlO3 films remained amorphous with postdeposition annealing up to 1000 °C. The leakage current density was 8.3×10−5 A/cm2 at −1 V. The low leakage current was attributed to the high barrier height of Al/LaAlO3 interface. The Al/LaAlO3 barrier height and the effective electronic mass calculated from Schottky emission and Fowler–Nordheim tunneling were 1.12 eV and 0.27m0, respectively. The dominant conduction mechanism in the temperature range of 300 K<T<420 K was space-charge-limited current, and the trapping depth was determined to be 0.36±0.1 eV.

Electrical Characterization and Dielectric Properties of Metal–Oxide–Semiconductor Structures Using High-κ CeZrO4 Ternary Oxide as Gate Dielectric

In this work, high-κ cerium zirconate (CeZrO4) was successfully fabricated by RF magnetron cosputtering with a postannealing temperature of 850 °C. The amount of Zr in CeO2 can be well controlled by adjusting the DC power of the Zr target. X-ray photoelectron spectroscopy (XPS) shows that CeZrO4 becomes amorphous with increasing DC power. The intensity of the CeZrO4 phase increases with increasing oxygen content in the plasma. The crystalline phases were confirmed using X-ray diffraction (XRD). The dielectric constant and flatband voltage shift (ΔVFB) as functions of DC power and oxygen gas flow rate were investigated. The optimum balance between leakage and dielectric constant was considered. The leakage current densities were 3×10-3 and 3×10-5 A/cm2 obtained at +2 and -2 V biases, respectively. A relative dielectric constant (er) of 24.3 and an effective oxide thickness (EOT) of 1.7 nm were achieved.

The Electrical and Interfacial Properties of Metal-High-

LaAlO3 is a promising candidate for gate dielectric of future VLSI devices. In this letter, n-channel metal-oxide-semiconductor field-effect transistors with LaAlO3 gate dielectric were fabricated, and the electron mobility degradation mechanisms were studied. The leakage current density is 7.6times10-5 A/cm2 at -1 V. The dielectric constant is 17.5. The surface-recombination velocity, the minority-carrier lifetime, and the effective capture cross section of surface states were extracted from gated-diode measurement. The rate of threshold voltage change with temperature (DeltaVT/DeltaT) from 11 K to 400 K is -1.51 mV/K, and the electron mobility limited by surface roughness is proportional to Eeff -0.66.

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Metal-oxide-semiconductor capacitors with Sm 2 O 3 dielectric film were fabricated and the temperature dependence of the conduction mechanisms was studied. The Sm 2 O 3 films were deposited by radio frequency magnetron sputtering. The thickness of Sm 2 O 3 was 18.8 nm. The dielectric permittivity and the equivalent oxide thickness of capacitors with Sm 2 O 3 film were 15.0 and 4.8 nm, respectively. The X-ray photoelectron spectroscopy analysis showed a silicate interfacial layer formed between Sm 2 O 3 and Si. When the aluminum electrode was biased positive, the dominant conduction mechanism was Schottky emission in the temperature range 475 K < T < 500 K and at an electrical field of 0.8 MV/cm < E < 1.4 MV/cm. In the temperature range 300-425 K, the dominant conduction mechanism was most likely space-charge-limited conduction. When the aluminum electrode was biased negative, the dominant conduction mechanism in the temperature range from 325 to 500 K and at an electrical field from 0.08 to 0.81 MV/cm was Schottky emission. At 77 K and with the electrical field above 0.9 MV/cm, the conduction mechanism was Fowler-Nordheim (F-N) tunneling. The Al/Sm 2 O 3 electron barrier height and the effective electronic mass calculated from Schottky emission and F-N tunneling were 0.82 eV and 0.13 m 0 , respectively.

Oxide-Semiconductor Field-Effect Transistors With

The positive bias temperature instability of n-channel metal-oxide-semiconductor field-effect transistors with ZrO2 gate dielectric was studied. It was observed that the degradation in threshold voltage (ΔVT) has an exponential dependence on the stress time in the temperature range from 25to75°C. The measurement of subthreshold slope (ΔS) during stress indicates that the degradation in VT is due to the interface trap charges Qit. The extracted activation energy of 0.3–0.5eV is related to a degradation dominated by the release of atomic hydrogen in the Si–ZrO2 interface.

\hbox{LaAlO}_{3}

LaAlO3 is a promising candidate of gate dielectric for future very large scale integration devices. In this work, metal-oxide-semiconductor capacitors and transistors with LaAlO3 gate dielectric were fabricated and the electron mobility degradation mechanisms were studied. The LaAlO3 films were deposited by radio frequency magnetron sputtering. The LaAlO3 films were examined by x-ray diffraction, secondary ion mass spectroscopy, and x-ray photoelectron spectroscopy. The temperature dependence of metal-oxide-semiconductor field-effect transistors characteristics was studied from 11 K to 400 K. The rate of threshold voltage change with temperature (ΔVT/ΔT) is −1.51 mV/K. The electron mobility limited by surface roughness is proportional to Eeff−0.66 in the electric field of 0.93 MV/cm<Eeff<2.64 MV/cm at 300 K and the phonon scattering is proportional to T−5.6 between 300 and 400 K. Soft optical phonon scattering was used to explain the extra source of phonon scattering in LaAlO3-gated n-channel metal-oxide-...

Gate Dielectric

ABSTRACT Metal-oxide-semiconductor (MOS) capacitors and transistors with Sm2O3 and Dy2O3 gate dielectrics were fabricated. The effective electron mobilities of Sm2O3-and Dy2O3-gated transistors were 211 and 251 cm2/V-s, respectively. The conduction mechanism in Sm2O3 films was also studied. The conduction mechanism in the electrical field of 0.1 MV/cm < E < 0.8 MV/cm and in the temperature range of 325 K < T < 500 K was found to be Schottky emission. At 77 K and with the electrical field above 0.9 MV/cm, the conduction mechanism was Fowler-Nordheim tunneling. The surface roughnesses at the high-k/Si interface after various annealing processes were measured by atomic force microscope.

Temperature Dependence of the Current Conduction Mechanisms in Sm2O3 Thin Films

Metal-oxide-semiconductor field-effect transistors with CeO2∕HfO2 laminated gate dielectrics were fabricated. The transistors have a subthreshold slope of 74.9mV/decade. The interfacial properties were measured using gated diodes. The surface state density Dit was 9.78×1011cm−2eV−1. The surface-recombination velocity (s0) and the minority carrier lifetime in the field-induced depletion region (τ0,FIJ) measured from the gated diode were about 6.11×103cm∕s and 1.8×10−8s, respectively. The effective capture cross section of surface state (σs) extracted using the subthreshold-swing measurement and the gated diode was about 7.69×10−15cm2. The effective electron mobility of CeO2∕HfO2 laminated gated transistors was determined to be 212cm2∕Vs.