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In this article, the authors report on thin film transistors based on gas phase synthesized ZnO nanoparticles using low temperature deposited silicon dioxide and silicon nitride as gate dielectrics. For bottom gate transistors, the devices using silicon nitride as gate insulator show the lowest off-current for a given induced charge and the steepest subthreshold slope. The charge carrier mobility of around 3×10-3 cm2/V s and an Ion/Ioff ratio of around 105 are almost independent of the insulator material. In a double gated thin film transistor using low stress silicon nitride as a top gate insulator, transistor parameters are extracted for the identical semiconducting layer when the bottom and top gates are used. It is shown that the extracted charge carrier mobility is not inherent for the ZnO nanoparticle layer but rather an effective value for the device under investigation. [ABSTRACT FROM AUTHOR]

In this work, two different dielectric stacks consisting of silicon dioxide (SiO2) and silicon nitride (Si3N4) are analyzed regarding their suitability as dielectrics in a high voltage trench capacitor. The processing of the dielectric layers and the resulting edge-coverage in the trench holes are described. Voltage and temperature dependence of the trench capacitance are analyzed and compared with planar capacitors for reference. The leakage currents are measured and the current transport mechanisms are analyzed. The outstanding properties of the devices are a high capacitance per area (1.25 nF/mm2 for SiO2 and 1.5 nF/mm2 for Si3N4), a low temperature coefficient (SiO2: 18 ppm/K; Si3N4: 85 ppm/K from 25-100 °C), and a low leakage current (<1×10-6 A) for voltages up to 400 V for Si3N4. [ABSTRACT FROM AUTHOR]

While the debate about the exact cause of Fermi level pinning in metal-high-k dielectric gate stacks is ongoing, several solutions for engineering the threshold voltage Vt of the gate stacks have been proposed. Engineering the flat-band voltage Vfb translates into an effective control of the threshold voltage. This study uses ion implantation as a tool to adjust Vfb by doping the gate stack. It is shown that lanthanide implantation can modulate the effective work function for n-type gate electrodes. Ion implantation of dysprosium (Dy) and lanthanum (La) into the gate stack achieves significant flat-band voltage shifts of about -1 and -3 V, respectively, for a dose of 1×1014 cm-2. By increasing the implantation dose and energy, larger shifts in the flat-band voltage are obtainable. [ABSTRACT FROM AUTHOR]

In this article the application of thin high-k dielectrics as capping layers on oxide/nitride/oxide memory stacks with respect to suppression of electron injection from the gate electrode during erase operation is investigated. The authors demonstrate that hafnium silicate layers, with a dielectric constant of 17, as thin as 1 nm of physical thickness can clearly reduce electron injection and thereby prevent erase saturation. In theory, tunneling currents will be more strongly suppressed with increasing k values when keeping the equivalent oxide thickness constant. Therefore, the prevention of erase saturation will be further improved. However, titanium oxide as capping layer, which has a dielectric constant of 60, exhibits inferior erase performance due to a strong electron injection by field-enhanced thermal emission of electrons. This Poole-Frenkel conduction mechanism takes place along trapping sites 0.32 eV below the conduction band in the titanium dioxide. While the application of high-k materials can efficiently suppress erase saturation due to tunneling currents, this effect can be diminished by leakage currents along shallow trapping sites which occur in high-k dielectrics. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report on the applicability of gas phase synthesized ZnO nanoparticles for printed electronics. Electrical characteristics of thin film transistors with an active layer based on ZnO nanoparticle dispersions are presented. A low charge carrier mobility and a low I on/I off ratio are found for the devices when measured in nitrogen atmosphere. The mobility is limited by the rough interface between semiconductor and dielectric. Additional electrical measurements in dry air reveal a dependency of the I on/I off ratio on surface states of the ZnO particles. It is shown that adsorption of oxygen on ZnO nanoparticles leads to improved transistor characteristics. [ABSTRACT FROM AUTHOR]

Abstract: In this work, silicon insulator interfaces are characterized by detailed photocurrent analysis. Results obtained for a variety of samples with different insulator layers and layer thicknesses are presented and discussed. The results show the applicability of the technique for a reliable process control and include data on high-k layers for the first time. Comparison of experiment and simulation is used to explain the injection level dependence of the measurements. [Copyright &y& Elsevier]

For future technology generations, the replacement of silicon dioxide as gate dielectric in metal-oxide–semiconductor devices becomes a challenging issue. Metal silicates are promising candidates in this context. In this paper, the potential of zirconium silicate films obtained by metal-organic chemical vapor deposition from a novel single-source precursor is shown. On basis of metal–insulator–semiconductor capacitors, data from capacitance–voltage, current–voltage, constant voltage stress, and constant current stress measurements are presented. Detected charge trapping phenomena, conduction mechanisms, and polarity dependence of device degradation are discussed. [Copyright &y& Elsevier]

The potential of zirconium silicate films as an alternative gate dielectric to silicon oxide in future technology generations is demonstrated. Novel single-source precursors for metal organic chemical vapor deposition (MOCVD) of zirconium silicate films are presented. These precursors meet the demands for implementation in a MOCVD process in respect to purity, volatility, and deposition temperature. Zirconium silicate layers were deposited and metal insulator semiconductor capacitors were manufactured. Structural characterization of the films was performed by means of X-ray photoelectron spectroscopy, secondary neutral mass spectroscopy, transmission electron microscopy, and ellipsometry. It was found that the silicon content in the zirconium silicate films is less than stoichiometric and carbon free films can only be obtained at deposition temperatures above 550 °C. The permittivity of the films is about 10.5–15. Electrical characterization by capacitance as a functions of voltage and current as a function of voltage measurement techniques show very promising results: low leakage current (5 × 10−9 A/cm2 at −3 V), low level of bulk charge (5 to 6 × 1011 cm−2), and small hysteresis (about 50 mV) were obtained. However, some instabilities, i.e negative charge trapping (up to 2 × 1012 cm−2) during electrical stress, have also been encountered and further investigations should aim at reducing this charge trapping. [Copyright &y& Elsevier]

Barium impact on the gate oxide breakdown was studied using E -ramp and constant current stress (CCS) charge to breakdown. Wafers were contaminated with Ba after a 7.5 nm gate oxide growth and 300 nm poly-silicon deposition. The measurements were done on capacitors having areas of 0.1, 1, 4, and 16 mm 2 . Up to a contamination level of 4×10 14 atoms/cm 2 no degradation in oxide integrity was observed either by E -ramp or CCS. Time of flight (ToF)-SIMS measurement of Ba diffusion profile at 800 °C shows a diffusion of Ba over distances of some tens of nanometers, thus Ba does not reach the gate oxide region. The effect on the gate oxide breakdown can be correlated with the slow diffusion of Ba in poly-Si. Therefore, no major concern of yield and reliability due to Ba contamination is seen for the integration of Ba containing dielectrics into memories. [ABSTRACT FROM AUTHOR]