Ming-Tsong Wang

Superconductivity in Ru-based double pervoskite - the possible existence of a new superconducting pairing state

Abstract We have studied the double perovskite structure A 2 Y(Ru 1−x Cu x )O 6 (A  Ba or Sr) system. The parent compounds are antiferromagnetic insulators. Partial substitution of the Ru-ion by Cu was found to induce superconductivity in these compounds. We also observed in these materials the coexistence of superconductivity and anomalous magnetic orders. Resistive measurements in high magnetic fields show that the field dependence of the transition temperatures is significantly different from those observed in high T c cuprates. Our results suggest that the pairing state of these new materials may be of odd parity such as p-wave.

Electrical conduction mechanism in high-dielectric-constant ZrO2 thin films

The electrical conduction mechanism in zirconium oxide (ZrO 2 ) thin films as a function of temperature T and electric field E was studied. Al/ZrO 2 /p-Si metal-insulator-semiconductor (MIS) capacitors were fabricated. With the Al electrode biased negative, the conduction mechanism in the electrical field of 0.81 MV/cm < E < 1.40 MV/cm and in the temperature range of 375 K < T < 450 K is found to be modified Schottky emission. The intrinsic barrier height between Al and ZrO 2 is 1.06 eV. At higher electrical fields of 1.50 MV/cm < E < 2.25 MV/cm and higher temperatures of 375 K < T < 450 K, the electrical conduction is dominated by modified Poole-Frenkel emission. The extracted trap barrier is 0.83 eV. With the Al electrode biased positive, the conduction mechanism is found to be Schottky emission at the electrical field 0.20 MV/cm < E < 0.60 MV/cm and higher temperature range of 425 K < T< 450 K. The barrier height between Si and ZrO 2 is 1.0 eV. Based on these results, an energy band diagram of the Al/ZrO 2 /p-Si system is proposed.

Stress Migration and Electromigration Improvement for Copper Dual Damascene Interconnection

Stress migration (SM) and electromigration (EM) were widely used to study the performance of interconnection process of metal/via formation in copper dual damascene of wafers. Necking and voids at the via bottom were important in causing failures in tests of stress migration and electromigration. In this report, the contamination of the bottom of via, which results in poor step coverage, the adhesion of seed layers, and poor copper grain formation are identified to be the underlying causes of the necking and void formation after the first EM and SM tests are performed. The contamination of the via formation processes included via etching, trench etching, and barrier/seed layer depositions. A well-shaped via profile can be optimized using three methods, the first involves Cu/SiN interface stress, the second involves Cu grain growth, and the third involves post via etching clean study. Eliminating the contamination of the via bottom and optimizing step coverage and adhesion of the barrier seed layers improve the EM and SM performance from time-to-fail = 13 to 59 s, in the copper-related processes for fabricating 300 mm wafers using technology that is beyond 0.13 μm technology.

The Ohmic Conduction Mechanism in High-Dielectric-Constant ZrO2 Thin Films

Al/ZrO 2 /p-Si metal-insulator-semiconductor capacitors were fabricated. The ZrO 2 films were deposited by radio frequency magnetron sputtering. The X-ray photoelectron spectroscopy analysis shows the silicate interfacial layer formed between ZrO 2 and Si. The hysteresis and the density of positive oxide trapped charges of the capacitors from capacitance-voltage measurement were 230 mV and 8.8 X 10 1 1 cm - 2 , respectively. The equivalent oxide thickness of ZrO 2 was estimated to be 5.6 nm. The typical dielectric constant of 11.1 was calculated. With the Al electrode biased negative, the conduction mechanism in the electrical field below 0.25 MV/cm and in the temperature range 375 K < T < 450 K was found to be ohmic emission. A model of thermally excited and hopping electrons was proposed to explain the mechanism of ohmic conduction current.

Temperature Dependence of the Tunnel-Emission Conduction Current in Metal- ZrO2-Silicon Capacitor Structures

Zirconium oxide (ZrO 2 ) is considered as a potential replacement for SiO 2 due to its high dielectric constant. The Al/ZrO 2 /p-Si metal-insulator-semiconductor capacitors were fabricated. The electrical conduction mechanism in zirconium oxide (ZrO 2 ) thin films as a function of temperature T and electric field E was studied. The temperatures measured were 77 K and from 300 to 450 K. With the Al electrode under negative bias, the conduction mechanism in the electric field of 2.3 MV/cm < E < 5 MV/cm and at the temperature 77 K is found to be Fowler-Nordheim tunneling emission. The extracted barrier height between Al and ZrO 2 is 1.12 eV. At the electric field of 1.5 MV/cm < E < 4 MV/cm and temperatures of 300 K < T < 450 K, the electrical conduction is dominated by tunnel emission of trapped electrons with an extracted trap barrier height of 0.19 eV at 300 K. The trap barrier height decreases as the temperature increases. This Al/ZrO 2 barrier height decreases linearly with temperature with a slope of about -7.0 X 10 - 4 eV/K. The lowering of the barrier height is explained by bandgap reduced with increasing temperature.

Electrical Conduction Mechanism in Metal- ZrO2-Silicon Capacitor Structures

The electrical conduction mechanism in zirconium oxide (ZrO 2 ) thin films as a function of temperature T and electric field E was studied. Al/ZrO 2 /p-Si metal-insulator-semiconductor capacitors were fabricated. With the Al electrode biased negative, the conduction mechanism in an electrical field of 0.81 < E < 1.40 MV/cm and in the temperature range of 375 < T < 450 K was modified Schottky emission. The intrinsic barrier height between Al and ZrO 2 was 1.06 eV. At a higher electrical field of 1.50 < E < 2.25 MV/cm and higher temperatures of 375 < T < 450 K, the electrical conduction was dominated by modified Poole-Frenkel emission. The extracted trap level was 0.83 eV. With the Al electrode biased positive, the conduction mechanism was Schottky emission at the electrical field 0.20 < E < 0.60 MV/cm and higher temperatures of 425 < T < 450 K. The barrier height between Si and ZrO 2 was 1.0 eV. Based on the above results, an energy band diagram of the Al/ZrO 2 /p-Si system is proposed.

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.

\kappa

The mobility degradation mechanism of n-channel metal-oxide-semiconductor field-effect transistors (n-MOSFETs) with ZrO2 gate dielectric was studied. The temperature dependence of device characteristics was studied in the temperature range from 300to420K. The electron mobility limited by surface roughness is proportional to Eeff−0.68 in the fields of 0.5<Eeff<2MV∕cm at 300K. The electron mobility limited by phonon scattering is proportional to T−3.0 at the effective normal field Eeff of 0.8MV∕cm between 300 and 420K. Soft optical phonon scattering was used to explain the extra source of phonon scattering in ZrO2-gated n-MOSFETs.

Oxide-Semiconductor Field-Effect Transistors With

Abstract We have achieved the preparation of the Y ( Ba 1− x Sr x ) 2 Cu 3 O 7 compounds with x ranging from 0 to 1 by substituting a small amount of Cu with Mo. It was observed that the superconducting transition temperature, T c , first decreases linearly with Sr-content until x 0.4, where a sharp drop in T c occurs. The T c for the sample with x =0.1 is about 40 K. X-ray structure analysis shows that a sharp drop in T c at a critical concentration corresponds to the crystal change from orthorhombic to tetragonal.

\hbox{LaAlO}_{3}

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.