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Al2O3-based dielectrics are currently considered as promising materials to use in nonvolatile memories. The electron trap density in this material is much higher than in conventional SiO2, being their characteristics critical for the application. Conventional capacitance-voltage (C-V) techniques were used to study the main effects of the electron traps on the electrical characteristics of MOS capacitors with atomic layer deposited Al2O3 as insulating layer. More detailed information about the trapping kinetics was obtained through the study of the constant capacitance voltage transient. Two different types of traps were found. One is responsible for the instabilities observed in C-V measurements, the other has characteristic trapping times three orders longer. A physical model is presented to explain the observed trapping kinetics exhibiting good agreement between experiments and simulations. The energy levels of the studied traps were determined at 2.2 and 2.6 eV below the Al2O3 conduction band, with densities of 2.9 × 1018 cm−3 and 1.6 × 1018 cm−3, respectively.

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The -radiation effects on the electrical characteristics of MIS capacitors based on HfO 2 , and on the resistive switching characteristics of the structures have been studied. The HfO 2 was grown directly on silicon substrates by atomic layer deposition. Some of the capacitors were submitted to a  ray irradiation using three different doses (16, 96 and 386 kGy). We studied the electrical characteristics in the pristine state of the capacitors. The radiation increased the interfacial state densities at the insulator/semiconductor interface, and the slow traps inside the insulator near the interface. However, the leakage current is not increased by the irradiation, and the conduction mechanism is Poole-Frenkel for all the samples. The switching characteristics were also studied, and no significant differences were obtained in the performance of the devices after having been irradiated, indicating that the fabricated capacitors present good radiation hardness for its use as a RS element.

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Techniques based on bias switching during the irradiation allow to extend the measurement range of MOS dosimeters. To well predict the response of these sensors under operation conditions it is mandatory to understand the physical phenomena involved. A physics-based numerical model is presented here to reproduce the response of MOS dosimeters under switched bias irradiations. Reported non-monotonic responses after a bias switch were previously explained by the presence of two types of hole traps with different characteristic times. The model presented in this work shows that this behavior can be explained by the spatial charge redistribution using a single trap. The electric field dependences of hole capture and neutralization rates are analyzed and compared with previous experimental results and models in the literature. The spatial distribution of hole traps within the oxide is also analyzed.

We propose the use of a CMOS differential circuit with inherent amplification to enhance the performance of n-channel field oxide MOSFETs as ionizing radiation dosimeters. These new dosimeters are aimed to be used in low dose applications such as X-ray diagnosis. The circuit is presented and described, and a discrete-level prototype was tested as regards sensitivity, temperature variations compensation and signal-to-noise ratio at different operation conditions. Results show that, comparing to a single MOSFET dosimeter, on chip amplification is possible along with temperature induced error attenuation. The highest sensitivity measured with respect to radiation was 0.4 V/rad. The circuit successfully measured the dose delivered in an X-ray image diagnosis environment with a sensitivity of approximately 0.5 V/rad.