Cheng-Ji Xian

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.

Electrical properties of Bi2Mg2∕3Nb4∕3O7 (BMN) pyrochlore thin films deposited on Pt and Cu metal at low temperatures for embedded capacitor applications

200-nm-thick BMN films were deposited on Pt∕TiO2∕SiO2∕Si and Cu∕Ti∕SiO2∕Si substrates at various temperatures by pulsed laser deposition. The dielectric constant and capacitance density of the films deposited on Pt and Cu electrodes show similar tendency with increasing deposition temperature. On the other hand, dielectric loss of the films deposited on Cu electrode varies from 0.7% to 1.3%, while dielectric loss of films on Pt constantly shows 0.2% even though the deposition temperature increases. The low value of breakdown strength in BMN films on Pt compared to films deposited on Cu electrode was attributed to the increase of surface roughness by the formation of secondary phases at interface between BMN films and Pt electrodes.

Transparent Capacitor for the Storage of Electric Power Produced by Transparent Solar Cells

Transparent Al 0.016 In 0.003 Zn 0981 O (AIZO)/Bi 2 Mg 2/3 Nb 4/3 O 7 (BMN)/AIZO capacitors were prepared using BMN films grown from 25 to 250°C on AIZO/glass substrates (Corning 1737) by pulsed laser deposition. The BMN films grown at 250°C on the AIZO electrode exhibit a stable interface state between BMN and AIZO electrodes and the lowest root mean square roughness of 1 nm. The Pt/200 nm thick BMN/200 nm thick AIZO capacitors show dielectric constants of 50―68, dielectric losses of 2―3%, and leakage current densities of ∼4 × 10 ―8 A/cm 2 at 200 kV/cm in the range of growth temperatures. The AIZO/BMN/AIZO capacitors exhibit irregular variations in transmittance in the visible range and an optical transmittance of approximately 94% at a wavelength of 550 nm. Transparent AIZO/BMN/AIZO capacitors are possible candidates for integration with the transparent solar cells for the transparent system applications.

Effect of thickness on electrical properties of bismuth-magnesium niobate pyrochlore thin films deposited at low temperature

Bi2Mg2∕3Nb4∕3O7 (BMN) pyrochlore thin films were deposited at 25 and 100°C on Cu∕Ti∕Si substrates by pulsed laser deposition. Dielectric and leakage current properties of BMN films are investigated as a function of film thickness. The critical thicknesses showing the thickness dependence of dielectric constant are approximately 50 and 70nm in BMN films deposited at 25 and 100°C, respectively. The capacitances of interfacial layers in the films deposited at 25 and 100°C are approximately 5.5 and 3.9pF, respectively. The thickness dependence of leakage current characteristics was attributed to the copper diffusion into the BMN films. An intrinsic conduction of BMN films was controlled by Schottky emission and the barrier height was estimated as 0.9–1.2eV in the temperature range from 25to100°C. Film thickness in terms of leakage current characteristics is limited above 100nm for embedded capacitor applications.

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.

Experimental investigation of interfacial and electrical properties of post-deposition annealed Bi2Mg2/3Nb4/3O7 (BMN) dielectric films on silicon

The effects of post-deposition annealing process on the material and electrical properties of radio frequency (RF) reactive magnetron sputter-deposited Bi2Mg2/3Nb4/3O7 (BMN) dielectric films integrated with silicon were investigated. All post-deposition annealed samples show the presence of a silicate-type amorphous interfacial layer. The films show smooth, continuous, crack-free surfaces and preserve an amorphous phase up to an annealing temperature of 700 ◦ C. The samples subjected to rapid thermal annealing in O2 ambient and subsequently in N2 ambient exhibit enhanced electrical characteristics, such as low values of capacitance equivalent thickness, interface state density, trap oxide charge density, reduced hysteresis and frequency dispersion, low leakage current, together with high electric field breakdown. These values are comparable to those of some of the most widely investigated high-k gate dielectrics.

Improvement of Leakage Current Characteristics by Plasma Treatment in Bi2Mg2 ∕ 3Nb4 ∕ 3O12 Dielectric Thin Films

Bismuth magnesium niobate (BMN) thin films deposited on Cu/Ti/Si substrates at 100°C by pulsed laser deposition were investigated for the effect of plasma treatment on dielectric and leakage current characteristics. The dielectric constant and dissipation factor of 60 nm thick films slightly decrease with increasing oxygen content in atmosphere of plasma treatment. The leakage current densities were improved with increasing oxygen content. The capacitance density and breakdown voltage of the films treated with N 2 :O 2 = 100:100 seem (standard cm 3 /min) were approximately 520 nF/cm 2 and 3 V, respectively. On the other hand, 100 nm thick BMN films treated by plasma at N 2 :O 2 = 100:100 sccm exhibit a leakage current density of approximately 6 X 10 -7 A/cm 2 at 10 V and a breakdown voltage above 10 V which is possible for embedded capacitor applications.

Effect of Deposition Temperature on Al0.016In0.003Zn0.981O Thin Films Grown on Glass Substrates by Pulsed Laser Deposition

The Al 0.016 Zn 0.984 O (AZO) and Al 0.016 In 0.003 Zn 0.981 O (AIZO) thin films were grown on Coming 1737 glass substrates by pulsed laser deposition and they were investigated for the structural, electrical, and optical properties as a function of deposition temperature. The crystallinity of the films increases with increasing deposition temperature and exhibits the close relationship with the resistivity of the films. A decrease of carrier concentrations with increasing deposition temperature was attributed to the reduction of the oxygen vacancies existing within the AZO and AIZO films. An increase of the mobility with increasing deposition temperature was attributed to the decrease of the ionized scattering defects such as oxygen vacancies. The crystallinity, resistivity, and optical transmittance of the AIZO films are superior compared with the AZO films in the range of deposition temperature from 25 to 200°C. The resistivity and the optical transmittance at a wavelength of 480 nm in the case of AZO films are approximately 7.3 X 10 -4 Ω cm and 87%, respectively. The resistivity and the optical transmittance of the AIZO films are approximately 4.5 X 10 -4 Ω cm and 93%, respectively.

Electrical Property and Long-Term Stability of Transparent Capacitors Using Multi-Layer Transparent Conducting Oxide Electrodes

Transparent capacitors of Al0.016In0.003Zn0.981O (AIZO)/Ag/AIZO/Bi2Mg2/3Nb4/3O7 (BMN)/AIZO/glass were prepared using BMN films with various thicknesses grown on AIZO/glass (Corning 1737) substrates by pulsed laser deposition. The BMN films deposited at 150 °C on the AIZO electrode exhibited a dielectric constant of 49–55, a dielectric loss of 3–7% at the frequency of 100 kHz and the leakage current densities of ~10-8 A/cm2 at 200 kV/cm, in the range of the thickness from 50 to 200 nm. After damp heat treatment for 300 h under the condition of 85% relative humidity at 85 °C, the electrical properties in the BMN capacitors were slightly degraded. The AIZO/Ag/AIZO/BMN/AIZO capacitors maintained the optical transmittance of approximately 77% at a wavelength of 500 nm after damp heat treatment.