256 research outputs found
Electrical Characterization at a Nanometer Scale of Weak Spots in Irradiated SiO2 Gate Oxides
No full textIn this work, the electrical conduction of irradiated thin SiO2 gate oxides of MOS structures has been analyzed at a nanometer scale with a Conductive Atomic Force Microscope (C-AFM). The results have been compared to those obtained on fresh and electrically stressed oxides, demonstrating the capability of the technique to evaluate the electrical damage induced during irradiation
Peculiar characteristics of nanocrystal memory cells programming window
No full textIn this work the authors study nanocrystal memory cells, focusing on a peculiar characteristic of these devices: the programming window measured in subthreshold region is larger than that measured in linear region. For converse, floating gate flash memory cells with a similar structure feature the same programming window in linear and subthreshold regions. To understand the cause of the difference observed in the nanocrystal memory cells, the authors perform two dimensional technology computer aided design simulations. They well reproduce the experimental results, indicating that the difference observed in nanocrystal memories is due to the localization of the charge into specific regions of the oxide above the channel, i.e., the nanocrystals. On the other hand, when the charge is uniformly stored in the oxide above the channel (as in the case of floating gate flash memory cells), this difference disappears
Effects of the Localization of the Charge in Nanocrystal Memory Cells
No full textIn this paper, we present a peculiar characteristic of nanocrystal (NC) memory (NCM) cells: The programming (P) windows measured in linear and subthreshold regions are different. A floating-gate Flash memory cell with a similar structure does not show the same behavior, and the P window (PW) is independent of the current level of the extrapolation, as expected. By performing 2-D TCAD simulations, we demonstrated that this characteristic of NCM cells is due to the localization of the charge into the NCs. We investigate the correlation between the difference of the PWs in linear and subthreshold regions and the number, width, and position of the NCs
Leaky spots in irradiated SiO2 gate oxides observed with C-AFM
No full textA conductive atomic force microscope (C-AFM) has been used to perform a nanometer scale characterization of the electrical properties of irradiated thin SiO2 gate oxides of MOS devices. The results have been compared to those obtained on fresh (without irradiation) and electrically stressed oxides. The electrical images reveal the existence of weak spots, which have been attributed to the electrical damage induced by irradiation. Their I-V characteristics have been registered with the C-AFM. The results show that they have a leaky behaviour, which has been associated to the radiation induced leakage current (RILC)
Implanted and irradiated SiO2/Si structure electrical properties at the nanoscale
No full textIn this work, a conductive atomic force microscope (C-AFM), a scanning capacitance microscope (SCM), and a kelvin probe force microscope (KPFM) have been used to qualitatively study at the nanoscale the electrical properties of irradiated and implanted gate oxides of metal-oxide-semiconductor structures. These techniques have allowed to investigate the electrical conduction (C-AFM) and the presence of charge (SCM and KPFM) in the oxide of the analyzed structures. The impact of the energy of the impinging ions has also been qualitatively evaluated
Gate dielectric degradation in CMOS inverters
No full textTo study the gate oxide degradation under stress conditions closer to the actual operation of devices in circuits, in this work, CMOS inverters have been stressed using DC and pulsed signals at the input. Uniform and non-uniform Fowler-Nordheim and Channel Hot Carrier stresses have been identified as those governing the oxide degradation, depending on the input signal, and modifying the electrical response of the device. In particular, a decrease of the saturation current is observed, which depends on the transistor type (NMOS or PMOS), input signal, and stress time. The results show larger degradations in the NMOS when the input frequency is increased, which has been attributed to the Channel Hot Carriers contribution during the output state transitions in the inverter. Also the impact of the different stresses on the circuit Output is analyzed and related to the degradation of the devices. A shift in the inverter voltage transfer characteristic has been observed. whose direction depends on the degradation that the transistors have suffered, being more important at elevated frequencies
Protocol for the Generation of Definitive Hematopoietic Progenitors from Human Pluripotent Stem Cells
No full textThis protocol offers a detailed procedure for the in vitro differentiation of human pluripotent stem cells (hPSCs) to multipotent hematopoietic progenitors that arise from SOX17+ hemogenic endothelium, mimicking intra-embryonic, HOXA-positive, aorta-gonad mesonephros (AGM) hematopoiesis. The generated endothelium displays transcriptional similarities to cells sorted from human 5-week AGM, and CD45+CD34+RUNX1C+ progenitors share an accessible chromatin profile with adult hematopoietic stem cells and multipotent progenitors. Therefore, this protocol is suitable for the mechanistic study of human multipotent progenitor development and for modeling childhood leukemias. For complete details on the use and execution of this protocol, please refer to Nafria et al. (2020).</p
Channel-Hot-Carrier Degradation and Bias Temperature Instabilities in CMOS Inverters
No full textThe degradation of NMOS and PMOS transistors within CMOS inverters has been analyzed. Channel-hot-carrier (CHC) degradation and/or bias temperature instabilities (BTIs) are identified as aging mechanisms, and their implications at the device and circuit levels are discussed. Device- and circuit-level results have been linked using the BSIM4 SPICE model
Using AFM related techniques for the nanoscale electrical characterization of irradiated ultrathin gate oxides
No full textWe used different atomic force microscopy (AFM) related techniques to analyze the electrical properties of ultrathin gate oxides irradiated with heavy ions, gathering information on the size, position, electrical properties, and number of conductive spots generated by the impinging particles. In particular, conductive-AFM (C-AFM), scanning capacitance microscopy (SCM), and Kelvin probe force microscopy (KPFM) have been used to measure at the nanoscale level the electrical conduction, capacitance, and contact potential, respectively, of fresh, irradiated, and electrically stressed MOS capacitors. The electrical properties of the different samples have been compared and the impact of the irradiation analyzed
Systematic characterization of soft- and hard-breakdown spots using techniques with nanometer resolution
No full textIn this work, different Atomic Force Microscopy (AFM) related techniques have been used to completely characterize soft- and hard-breakdown Spots Of SiO2 gate oxides. In particular, C-AFM (Conductive AFM), SCM (Scanning Capacitance Microscopy) and KPFM (Kelvin Probe Force Microscopy) were used to study the propagation, conduction and the electrical damage of previously broken down gate oxide areas. The results show that the combination of these techniques allows a complete and systematic study of the BD phenomenology at the nanoscale
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