Joo Young Choi

Electrical Properties of Amorphous Bi 5 Nb 3 O 15 Thin Film for RF MIM Capacitors

Amorphous Bi₅Nb₃O₁₅(B₅ N₃) film grown at 300degC showed a high-<i>k</i> value of 71 at 100 kHz, and similar <i>k</i> value was observed at 0.5-5.0 GHz. The 80-nm-thick film exhibited a high capacitance density of 7.8 fF/mum² and a low dissipation factor of 0.95% at 100 kHz with a low leakage-current density of 1.23 nA/cm² at 1 V. The quadratic and linear voltage coefficient of capacitances of the B₅N₃ film were 438 ppm/V² and 456 ppm/V, respectively, with a low temperature coefficient of capacitance of 309 ppm/degC at 100 kHz. These results confirmed the potential of the amorphous B₅N₃ film as a good candidate material for a high-performance metal-insulator-metal capacitors.

Effect of Oxygen Pressure on the Electrical Properties of

Bi₅Nb₃O₁₅ (B₅N₃) films grown under a low oxygen partial pressure (OP) of 1.7 mtorr showed a high leakage current density of 0.1 A/cm² at 1.0 MV/cm. However, the leakage current density decreased with increasing OP to a minimum of 5.8 times 10^-9 A/cm² for the film grown under 5.1 mtorr due to the decreased number of oxygen vacancies. This film also showed an improved breakdown field of 2.2 MV/cm and a large capacitance density of 24.9 fF /mum². The electrical properties of the film, however, deteriorated with a further increase in OP, which is probably due to the formation of oxygen interstitial ions. Therefore, superior electrical properties for the B₅N₃ film can be obtained by careful control of OP.

\hbox{Bi}_{5} \hbox{Nb}_{3}\hbox{O}_{15}

Te ions existed as Te 6+ in the Bi 6 Ti 5 TeO 22 (BTT) film grown at 300°C under a high oxygen pressure (OP) of 80.0 Pa and contributed to the formation of the crystalline BTT phase after subsequent annealing at 600°C. However, for the BTT film grown under a low OP of 53.3 Pa (or 9.33 Pa), Te 6+ ions, were converted to Te 4+ ions, which induced the phase transition of the BTT phase to the pseudo-Bi 4 Ti 3 O 12 and pseudo-Bi 2 Ti 2 O 7 phases after annealing at 600°C. The leakage current density decreased with increasing OP during the growth due to the decreased number of oxygen vacancies. The breakdown voltage also improved with increasing OP during the deposition. The Mn ions introduced in the BTT films by Mn doping existed as Mn 2+ or Mn 4+ and acted as the acceptors. This Mn doping to 10 mol % also reduced the leakage current density and increased the breakdown voltage by decreasing the number of intrinsic oxygen vacancies.

Films Grown by RF Magnetron Sputtering

Buckling was observed in Bi₅Nb₃O₁₅ (BiNbO) films grown on TiN/SiO₂/Si at 300°C but not in films grown at room temperature and annealed at 350 °C. The 45-nm-thick films showed a high capacitance density and a low dissipation factor of 8.81 fF/¿m² and 0.97% at 100 kHz, respectively, with a low leakage current density of 3.46 nA/cm² at 2 V. The quadratic and linear voltage coefficients of capacitance of this film were 846 ppm/V² and 137 ppm/V, respectively, with a low temperature coefficient of capacitance of 226 ppm/°C at 100 kHz. This suggests that a BiNbO film grown on a TiN/SiO₂/Si substrate is a good candidate material for high-performance metal-insulator-metal capacitors.

Oxygen Pressure and Mn-Doping Effects on the Structure and Leakage Current of Bi6Ti5TeO22 Thin Film

The amorphous Bi(5)Nb(3)O(15) film grown at room temperature under an oxygen-plasma sputtering ambient (BNRT-O(2) film) has a hydrophobic surface with a surface energy of 35.6 mJ m(-2), which is close to that of the orthorhombic pentacene (38 mJ m(-2)), resulting in the formation of a good pentacene layer without the introduction of an additional polymer layer. This film was very flexible, maintaining a high capacitance of 145 nF cm(-2) during and after 10(5) bending cycles with a small curvature radius of 7.5 mm. This film was optically transparent. Furthermore, the flexible, pentacene-based, organic thin-film transistors (OTFTs) fabricated on the poly(ether sulfone) substrate at room temperature using a BNRT-O(2) film as a gate insulator exhibited a promising device performance with a high field effect mobility of 0.5 cm(2) V(-1) s(-1), an on/off current modulation of 10(5), and a small subthreshold slope of 0.2 V decade(-1) under a low operating voltage of -5 V. This device also maintained a high carrier mobility of 0.45 cm(2) V(-1 )s(-1) during the bending with a small curvature radius of 9 mm. Therefore, the BNRT-O(2) film is considered a promising material for the gate insulator of the flexible, pentacene-based OTFT.

Electrical properties of Bi5Nb3O15 thin film grown on TiN/SiO2/Si at room temperature for metal - Insulator - Metal capacitors

Mn-doped Bi₄Ti₃O₁₂ (M-B₄T₃) films were well formed on a TiN/SiO₂/Si substrate at 200degC without buckling using RF magnetron sputtering. The leakage current density of these films was considerably influenced by the oxygen partial pressure (OPP), which was attributed to the presence of oxygen vacancies or oxygen interstitial ions. The film grown under 2.8-mtorr OPP showed the lowest leakage current density. The M-B₄T₃ films grown at 200degC showed a high dielectric constant of 38 with a low loss in both kilohertz and gigahertz ranges. The 39-nm-thick film showed a high capacitance density of 8.47 fF/mum² at 100 kHz, and its temperature and quadratic voltage coefficients of capacitance were low at approximately 370 ppm/degC and 667 ppm/V², respectively, with a low leakage current density of 7.8 times 10^-8 A/cm² at 2 V. Therefore, the M-B₄T₃ thin film grown on a TiN/SiO₂/Si substrate is a good candidate material for high performance, radio frequency metal-insulator-metal capacitors.

A Flexible Amorphous Bi5Nb3O15 Film for the Gate Insulator of the Low-Voltage Operating Pentacene Thin-Film Transistor Fabricated at Room Temperature

B1 6 Ti 5 TeO 22 (BTT) thin films were well formed on a Pt/Ti/SiO 2 /Si substrate using radio frequency magnetron sputtering. The dielectric constant (k) of the BTT films grown at room temperature was relatively high, approximately 54, and increased with increasing growth temperature to reach a maximum value of 107 for the film grown at 500°C. In particular, the 120 nm thick BTT films grown at 200-300°C showed high k-values of 63-69 with a low dissipation factor (< 1.3%) due to the presence of the small BTT crystals (∼5 nm). The leakage current density of this film was very low, approximately 2 X 10 -10 A/cm 2 , at 3 V. Therefore, the BTT film grown at low temperatures (≤300°C) is a promising candidate material for metal-insulator-metal capacitors which require low processing temperatures.