M. Zabala

Electrical characteristics of metal-insulator-semiconductor structures with atomic layer deposited Al2O3, HfO2, and nanolaminates on different silicon substrates

In this work, the electrical characteristics of different atomic layer deposited high-permittivity dielectric films (Al2O3, HfO2, and a nanolaminate of them), with a physical thickness of about 10 nm, are evaluated. An extensive capacitance-voltage and current-voltage characterization at room temperature is carried out on metal-insulator-semiconductor structures fabricated on different p-type and n-type silicon substrates and with Al as metal gate. HfO2 layers are found to exhibit the higher dielectric constant, but they suffer from the largest hysteresis and leakage currents and the lowest breakdown voltages. The nanolaminate stacks, with an intermediate dielectric constant, are found to exhibit more similarities to the Al2O3 layers, withstanding the largest voltages of all the studied dielectric films. The electrical degradation of the layers is evaluated by means of consecutive current-voltage ramps and with constant voltage stress experiments. Results on n-type Si, with electron injection from the sub...

Hydrogen-selective microelectrodes based on silicon needles

The fabrication of hydrogen-selective microelectrodes on silicon needle-shaped substrates is described. The microelectrodes are based on an ion-selective poly(vinyl chloride) (PVC) membrane with an intrinsically conducting polymer (polypyrrole (PPy)) solid contact layer. The polypyrrole is prepared with the dopant anion cobaltbis(dicarbollide) [3,3 0 -Co(1,2-C2B9H11)2] � , which gives a high stability to the polymer layer. The performance of the resulting solid-contact ion-selective microelectrodes (SCISME) is investigated by using potentiometric measurement and electrochemical impedance spectrometry. The feasibility of the fabrication technology is demonstrated and the devices operate satisfactorily, with a response showing good sensitivity and selectivity against common interfering cations in background solutions. The SCISME has been developed for organ monitoring during cardiac surgery or during transportation for transplants. # 2003 Elsevier Science B.V. All rights reserved.

Deposition Temperature and Thermal Annealing Effects on the Electrical Characteristics of Atomic Layer Deposited Al2O3 Films on Silicon

Atomic layer deposition (ALD) of Al 2 O 3 is of interest for a wide range of micro-nanoelectronic applications, where the electrical properties of the deposited layers can be strongly affected by deposition conditions and post-deposition treatments. In this work, a mercury-probe capacitance-voltage characterization is carried out on Al 2 O 3 films deposited on silicon by ALD at different temperatures and subjected to various thermal treatments in N 2 ambient. Effective positive charges located at the semiconductor/dielectric interface are encountered for the films deposited at the lowest temperature (100°C). Positive V fb shifts are always registered after the different thermal annealing conditions studied; however, the impact of the thermal treatments is found to be different depending on the deposition temperature. A significant negative charges build-up is observed after a 30 min anneal at 450°C, where improved surface passivation properties are achieved. Interestingly, the hysteresis, as well as the V fb shifts, clearly diminish for higher deposition temperatures or after a thermal anneal. However, the highest temperature treatments (≥800°C) result in significant interface states generation. Finally, exploratory experiments about the stability of the Al 2 O 3 layers under UV-light irradiation (in the 200-300 nm wavelengths range) show that this can be responsible for a significant degradation of their electrical characteristics.

Electrical characterization of high-k based metal-insulator-semiconductor structures with negative resistance effect when using Al2O3 and nanolaminated films deposited on p-Si

In this work, the results of the electrical behavior of metal-insulator-semiconductor (MIS) structures using Al2O3, HfO2, and nanolaminated layers as gate insulators are reported. The MIS structures were deposited by atomic layer deposition on several Si substrates. The authors observed different conduction mechanisms for these high-k based MIS structures depending on the bias regime. Direct tunneling, Fowler–Nordheim, Poole–Frenkel emission, and a negative resistance region have been observed at different gate voltage values. The tunneling conduction of majority and minority carriers assisted by defects located at the Al2O3/HfO2 and Al2O3/metal interfaces can explain the negative resistance behavior observed in Al2O3 and nanolaminated samples. In addition to current-voltage (I-V) measurements, MIS structures were also electrically characterized using capacitance-voltage (C-V), deep level transient spectroscopy, conductance transients (G-t), and flat-band voltage transient (VFB-t) techniques.

Charge trapping analysis of Al2O3 films deposited by atomic layer deposition using H2O or O3 as oxidant

In this work, the authors focus on the charge trapping behavior of Al2O3 layers deposited by atomic layer deposition. The goal is to give an insight into the effects of the oxidant source (H2O or O3) and the postdeposition anneal on the charging phenomena and the generation of new defects during electrical stress. For this purpose, current–voltage, capacitance–voltage, and conductance–voltage characteristics of Al/Al2O3/p-Si capacitors are analyzed before and after constant voltage stress and several phenomena such as the generation of neutral traps in the bulk dielectric, slow states, interface states, and charge trapping related degradation during the electrical stress are investigated. Finally, the impact of the oxidant source on the Al2O3 layer reliability is discussed.

Blistering of atomic layer deposition Al2O3 layers grown on silicon and its effect on metal–insulator–semiconductor structures

In this work, a study of the influence of the processing conditions on the blistering of Al2O3 layers grown by atomic layer deposition (ALD) on silicon substrates is presented. The phenomenon occurs when the as-deposited layers are annealed at high temperature in a N2 atmosphere. The characterization of the blistering in terms of density and dimensions indicates that the higher the annealing temperature the higher the density but also the smaller the blister diameter, while the thicker the oxide the larger the blisters. The processing of the blistered layers to obtain Al-Al2O3-Si structures enhances the blistering phenomenon and at the same time affects the silicon surface underneath the blister. This has been evidenced by chemical etching of the deposited layers that have revealed in circular silicon voids of the size of the blister. The influence of the oxygen precursor used in the ALD process has also been investigated, showing that the blister size is reduced when using O3 instead of H2O. Finally, the...

Electrical characterization of atomic-layer-deposited hafnium oxide films from hafnium tetrakis(dimethylamide) and water/ozone: Effects of growth temperature, oxygen source, and postdeposition annealing

The electrical properties of HfO2-based metal–insulator–semiconductor capacitors have been systematically investigated by means of I–V and C–V characteristics, admittance spectroscopy, deep level transient spectroscopy, conductance transient, and flat band voltage transient techniques. Attention is also given to the study of the temperature dependence of the leakage current. HfO2 films were grown on p-type silicon substrates by atomic layer deposition using hafnium tetrakis(dimethylamide) as hafnium precursor, and ozone or water as oxygen precursors. The growth temperature ranged from 150 to 350 °C. Low growth temperatures prevent decomposition and high growth rate, as well as high contamination levels. As a result, the leakage current is lower for lower deposition temperatures. Some of the deposited samples were submitted to a postdeposition annealing at 650 °C in N2 atmosphere, showing a decrease in the leakage current and an increase in the equivalent oxide thickness (EOT), whereas interfacial state de...

Comparison between Al 2 O 3 thin films grown by ALD using H 2 O or O 3 as oxidant source

Alumina (Al<inf>2</inf>O<inf>3</inf>) thin films have been deposited on silicon substrates by atomic layer deposition at 200°C using TMA as Al precursor and H<inf>2</inf>O or O<inf>3</inf> as oxygen precursor. The growth rate has been found to be lower for ozone-based processes as compared to H<inf>2</inf>O. The electrical characterization of the deposited layers has shown that when using O<inf>3</inf> the films exhibit larger defect densities as compared to those grown using H<inf>2</inf>O, although these show larger trapping. A post deposition anneal process at 650°C has been shown to lower the defect densities, being this annealing more efficient for O<inf>3</inf>-grown layers. The effect of post-metallization annealing in forming gas is also investigated.

Thin high-k dielectric layers deposited by ALD

In this paper first results on the growth of thin layers of Al2O3, HfO2 and nanolaminates of them, by Atomic Layer Deposition are reported. The electrical characterization of the deposited layers has been carried out by means of the analysis of the capacitance-voltage and current-voltage characteristics of Aluminum-high-k dielectric-Silicon capacitors. The obtained results show that for the same physical thickness, HfO2 layers are leakier than Al2O3 layers and that a nanolaminate stack of them improves the performance of the dielectric in terms of current and breakdown voltage although at the expense of a higher EOT.

Effect of the blistering of ALD Al 2 O 3 films on the silicon surface in Al-Al 2 O 3 -Si structures

Blistering of 11 nm and 45 nm-thick Al₂O₃ layers deposited by ALD on silicon substrates is studied in Al-Al₂O₃-Si structures fabricated using a field isolated process. Blisters are shown to be unevenly distributed and with different dimensions depending on the structure area. After chemical etching down to silicon, round voids are revealed underneath the blisters depending on the etchant used, indicating that some chemical reaction occurs at the Al₂O₃-Si interface at the blistered sites.