Nak-Jin Seong

Bismuth-zinc-niobate embedded capacitors grown at room temperature for printed circuit board applications

We fabricated metal-insulator-metal (MIM) thin film capacitors with Bi1.5Zn1.0Nb1.5O7 (BZN) dielectric films. The BZN films were deposited at room temperatures by pulsed laser deposition and annealed below 200°C which is compatible with the used polymer-based substrates. The dielectric constant of BZN films increases from 2 to 70, when they are annealed at 150°C, but still in amorphous phase. We found that a considerable portion of Bi metallic phase still remains in the as-deposited film. They turn into oxides upon annealing at >120°C, causing the dramatic change of the dielectric properties. Amorphous BZN thin films exhibit superior dielectric characteristics, capacitance density of 150nF∕cm2, and leakage current less than 1μA∕cm2 at 5V. The MIM capacitors using amorphous BZN thin films will be a promising candidate for the PCB-embedded capacitors.

Effects of Co-doping level on the microstructural and ferromagnetic properties of liquid-delivery metalorganic-chemical-vapor-deposited Ti1−xCoxO2 thin films

Polycrystalline Ti1−xCoxO2 thin films on SiO2 (200 nm)/Si (100) substrates were prepared using liquid-delivery metalorganic chemical vapor deposition, and the microstructure and ferromagnetic properties were investigated as a function of doped Co concentration. Ferromagnetic behaviors of polycrystalline films were observed at room temperature, and the magnetic and structural properties strongly depended on the Co distribution, which varied widely with doped Co concentration. The annealed Ti1−xCoxO2 thin films with x⩽0.05 showed a homogeneous structure without any clusters, and pure ferromagnetic properties of thin films are only attributed to the Ti1−xCoxO2 (TCO) phases. On the other hand, in case of thin films above x=0.05, Co1−xTix clusters having a soft magnetic (SM) property formed in a homogeneous Ti1−xCoxO2 phase, and the overall ferromagnetic (FM) properties depended on both FMTCO and SMCo–Ti. Co1−xTix clusters with about 150 nm size decreased the value of Hc (coercive field) and increased the satu...

Realization of a high capacitance density in Bi2Mg2∕3Nb4∕3O7 pyrochlore thin films deposited directly on polymer substrates for embedded capacitor applications

Bi2Mg2∕3Nb4∕3O7 (BMN) thin films were deposited on copper clad laminate substrates at temperatures below 150°C for embedded capacitor applications by pulsed laser deposition. The BMN films deposited at temperatures below 150°C showed smooth surface morphologies having root mean square roughness of approximately 3.0nm. 130-nm-thick films deposited at 150°C exhibit a dielectric constant of 47, a capacitance density of approximately 302nF∕cm2, and breakdown strength of 0.7MV∕cm. The origin exhibiting high dielectric constant in BMN films deposited at low temperatures was attributed to the nanocrystallines having grain sizes of approximately 4.0nm in the films. The low temperature processed-BMN films are suitable candidate for capacitor applications embodied directly on printed circuit board substrates.

Characterization of SrBi2Ta2O9 ferroelectric thin films deposited at low temperatures by plasma-enhanced metalorganic chemical vapor deposition

Ferroelectric bismuth-layer SrBi2Ta2O9(SBT) thin films were prepared on Pt/Ti/SiO2/Si substrate by plasma-enhanced metalorganic chemical vapor deposition. The films were crystallized at temperatures between 500 and 600 °C. The dielectric constant and dissipation factor of SBT films were 320 and 0.04 at an applied frequency of 1 MHz, respectively. The remanent polarization (Pr) and the coercive field (Ec) obtained for a 200 nm thick Sr0.9Bi2.3Ta2.0O9 films deposited at 550 °C were 15 μC/cm2 and 50 kV/cm at an applied voltage of 3 V, respectively. The leakage current density was about 5.0×10−8 A/cm2 at 300 kV/cm. The films showed fatigue-free characteristics up to 1.0×1011 switching cycles under 6 V bipolar pulse.

Nanoscale Silver-Based Al-Doped ZnO Multilayer Transparent-Conductive Oxide Films

Requirements of transparent-conductive oxide (TCO) films for solar cells and other optoelectronic applications are mainly focused on the electrical resistivity as low as 10- 5 Ω cm, optical transmittance above ∼85% in the visible region, a long-term stability in damp heat-treatment for 1000 h, a mechanical stability on flexible polymer substrates, and the large-area deposition technique for commercialization. In this study, the typical properties of the 45 nm thick Al-doped ZnO (AZO)/Ag/45 nm thick AZO multilayer films embedded by silver layers with various thicknesses were addressed to satisfy the requirements of TCO films for flexible electronic device applications. The AZO/9 nm thick Ag/AZO multilayer films as deposited on poly(ether sulfone) (PES) polymer substrates at 30°C by radio-frequency magnetron sputtering, which the deposition on large-area substrates is possible, exhibited the electrical resistivity of approximately 5 X 10- 5 Ω cm, optical transmittance of 88% at 550 nm wavelength, no appreciable change in electrical resistance and optical transmittance after damp heat-treatment for 1000 h, and a strong mechanical stability between multilayer films and PES substrates after a severe bending test. The results presented in the multilayer films can provide a platform for TCO films deposited on polymer substrates to enable the flexible electronic device applications.

Growth Mechanism of the Copper Oxide Nanowires from Copper Thin Films Deposited on CuO-Buffered Silicon Substrate

The growth mechanism of the CuO single-crystal nanowires (NWs) for future device applications has been demonstrated using the copper films deposited on CuO-buffered SiO 2 /Si substrates. The mechanism involves a two-step process: In the first step, hillocks of copper are formed to relieve the compressive stress existing on the copper films at high temperature for a long duration of time in air and then Cu 2 O phase is formed by the oxidation of the hillocks in air ambient. The second step involves a continuous supply of copper through the porous Cu 2 O seed and then the transformation of the Cu 2 O phase to CuO NW. The CuO NW was grown by a continuous supply of both copper from the copper films and oxygen from air. The indispensable requirements for CuO NW growth from the copper films are the presence of compressive stress in the copper films and the presence of the Cu 2 O seed phase on the copper films at a high temperature in air.

Effect of nitrogen incorporation on improvement of leakage properties in high-k HfO2 capacitors treated by N2-plasma

The nitrogen incorporation into the HfO2 films with an EOT (equivalent oxide thickness) of 9A was performed by N2-plasma to improve the electrical properties. The dielectric properties and a leakage current characteristics of the capacitors were investigated as a function of plasma power and plasma treatment temperature. The dielectric constant of the capacitors is not influenced by nitrogen incorporation. The N2-plasma treatment at 300°C and 70W exhibits the most effective influence on improvement of the leakage current characteristics. Leakage current density of the capacitors treated at 300°C and 70W exhibits a half order of magnitude lower than that without plasma treatment. Nitrogen incorporated into the HfO2 films possesses the intrinsic effect that drastically reduce the electron leakage current through HfO2 dielectrics by deactivating the VO (oxygen vacancy) related gap states.

Effect of indium concentration on the structural and electrical properties of Al-doped ZnO thin films grown by pulsed laser deposition

The Al-doped ZnO (AZO) films doped with different indium concentrations were grown on glass substrates (Corning 1737) at 200 °C by pulsed laser deposition. Indium doping in AZO films shows a critical effect on the crystallinity, resistivity and optical properties of the films. The AZO films doped with 0.3 atom% indium content exhibit the highest crystallinity, the lowest resistivity of 4.5 × 10−4 Ω cm and the maximum transmittance of 93%. The crystallinity of the indium doped-AZO films is strongly related to the resistivity of the films. The carrier concentration in the indium doped-AZO films linearly increases with increasing indium concentration. The mobility of the AZO films with increasing indium concentration was reduced with an increase in the carrier concentration and the decrease in mobility was attributed to the ionized impurity scattering mechanism. In optical transmittance, the shift of the optical absorption edge to a shorter wavelength strongly depends on the electronic carrier concentration in the films. The figure of merit FTC used for evaluating transparent electrodes reached 0.32 Ω−1 at 550 nm wavelength.

Bismuth-Based Pyrochlore Thin Films Deposited at Low Temperatures for Embedded Capacitor Applications

Various bismuth-based pyrochlore films were deposited on copper clad laminate substrates at temperatures below 150 °C by pulsed laser deposition for embedded capacitor applications. The films showed smooth and dense morphologies during deposition at room temperature. Bi2Mg2/3Nb4/3O7 (BMN) pyrochlore films showed the most stable dielectric properties and leakage current behaviors as a function of film thickness and deposition temperature. The capacitance density and breakdown field of 150-nm-thick-BMN films deposited at 150 °C were approximately 325 nF/cm2 and 410 kV/cm, respectively. The BMN films showed a dielectric constant of 55, a dielectric loss of 1.6% at 100 kHz, and a leakage current density of 1×10-8 A/cm2 at an applied field of 250 kV/cm. Metal/insulator/metal (MIM) capacitors including various bismuth-based pyrochlore films are expected to be promising candidates for printed circuit board (PCB)-embedded capacitors.

Effect of excess bismuth concentration on dielectric and electrical properties of fully crystallized Bi2Mg2∕3Nb4∕3O7 thin films

The fully crystallized Bi2Mg2∕3Nb4∕3O7 (BMN) films deposited at 400°C were characterized as a function of excess bismuth amount. The films with 15mol% excess bismuth amount were fully crystallized having a monoclinic structure at 300°C. The dielectric constant of the films deposited at 400°C increases with increasing excess bismuth amount and the films with 15mol% excess bismuth exhibit a dielectric constant of 128 and a dissipation factor of 0.2%. The crystallized BMN films with 170nm thickness exhibit breakdown strengths above 600kV∕cm (⩾10V), irrespective of excess bismuth amount and a leakage current density of 2×10−8A∕cm2 at 590kV∕cm. The conduction of crystallized BMN films was controlled by Schottky emission mechanism having a Schottky barrier height of 0.2–0.35eV.