Papers by Keyword: Threshold Voltage

Abstract: This article presents a review of various methods for extracting the key parameters of junctionless (JL) MOSFETs, namely, the threshold voltage, flat-band voltage, doping concentration, carrier mobility, and parasitic series resistance. The applicability and limitations of different methods are analyzed using numerical simulations and experimental data for planar and tri-gate nanowire JL transistors with various nanowire widths.

Abstract: In this paper, we have analyzed the effect of chiral vector, temperature, metal work function, channel length and High-K dielectric on threshold voltage of CNTFET devices. We have also compared the effect of oxide thickness on gate capacitance and justified the advantage a CNTFET provides over MOSFET in nanometer regime. Simulation on HSPICE tool shows that high threshold voltage can be achieved at low chiral vector pair in CNTFET. It is also observed that the temperature has a negligible effect on threshold voltage of CNTFET. After that we have simulated and observed the effect of channel length variation on threshold voltage of CNTFET as well as MOSFET devices and given a theoretical analysis on it. We found an unusual, yet, favorable characteristics that the threshold voltage increases with decreasing channel length in CNTFET devices in deep nanometer regime.

Abstract: A silicon substrate is the starting point of producing the semiconductor component, so that the quality of semiconductor substrate is very important during the VLSI fabrication. In this paper, we will evaluate the influence of MOS device characteristics under different oxygen impurities in silicon substrates. In the course of silicon substrate pulling process by Czochralski method, the defect and impurity will be existed; the oxygen atom will be induced substrate dislocations and affected the substrate quality. In this work, different oxygen doses will be used in wafer to study the impacts on MOS CV curve characteristic, interface trap charge characteristic, I_D-V_DS curve, I_D-V_GS curve, and threshold voltage behaviors of MOS devices.

Abstract: Current power MOSFET devices on Silicon Carbide show a limited inversion channel mobility, which can be a result of the expected very high density of interface states near the conduction band . In the current work, the effect of the post implantation annealing temperature, the thermal oxidation and the nitrogen doping of the n-epi layer on the density of these interface traps is investigated using capacity-conductance measurements. Instead of the usage of very high frequencies as used in , in this investigation the measurements were performed in liquid nitrogen to decrease the recharging times of the interface traps.Due to the different processing the samples showed a wide spreading of the inversion channel mobility. The conductance measurements show a characteristic peak caused by the conduction band near interface traps especially for the low temperature measurements. But these traps could not be correlated to the mobility. Instead, a correlation to the nitrogen doping of the epi layer could be observed.

Abstract: We proposed an improved method for evaluating the effective channel mobility (μ_eff), involving an appropriate definition of the threshold voltage (V_th) based on the ideal gate bias voltage – drain current (V_G-I_D) characteristics. Using this method, the dependence of μ_eff on the effective field (E_eff) could be evaluated even for SiC trench MOSFETs with large interface state density (D_it) values. The dominant influence on μ_eff in the low E_eff region was found to be Coulomb scattering caused by interface states at the SiC/SiO₂ interfaces.

Abstract: Long-term degradation of MOS devices has to be avoided in different harsh irradiated environments, especially for aerospace or military applications. In this paper, an overview of the irradiation experiments recently performed on 4H-SiC MOSFETs having an oxynitrided gate oxide is given, with a special focus on the threshold voltage and the effective channel mobility drifts. The general mechanisms taking place during irradiation and post-annealing treatments are described. Finally, new open issues recently observed by performing the temperature measurement on irradiated MOSFETs will be introduced and discussed.

Abstract: The effect of the Ge mole fraction in a Si_1-xGe_x on single and dual channel Vertical Strained SiGe Impact Ionization MOSFET was successfully analyzed. It is found that the threshold voltage, breakdown voltage and sub-threshold slope of the devices was affected by the presence of the Germanium. A better performance in sub-threshold voltage of the devices was obtained for dual channel VESIMOS compared to single channel VESIMOS with a suitable amount of Germanium. Germanium has high and symmetric impact ionization rates to ensure the transition from OFF state to ON state is abrupt. With the appearance of the SiGe layer in the devices, has an advantage of the mobility enhancement of carriers in the devices operation. With the improvement of the Ge composition, it could transform VESIMOS into a new paradigm of devices which applicable to nanoelectronics with better electrical characteristics.

Abstract: This work presents the 10 MeV protons irradiation effects on 4H-SiC MOSFETs at different fluences. MOSFETs main electrical parameters, such as the channel mobility (µ_EFF), threshold voltage (V_TH), transconductance (g_m) and subthreshold current, were analyzed using the time bias stress instability (BSI) technique. Applying this method allowed us to study the effect of carriers interaction with generated interface traps, whether in the bulk or at the interface. Improvements, such as V_TH stabilization in time and a significant increase of the µ_EFF at high fluencies, have been noticed. We assume that this behavior is connected with the atomic diffusion from the SiO₂/SiC interface, towards the epilayer during proton irradiation. These atoms, in majority Nitrogen, may create other bonds by occupying various vacancies coming from Silicon and Carbon’s dangling bond. Therefore, by enhancing the passivated Carbon atoms number, we show that high irradiation proton could be a way to improve the SiO₂/SiC interface quality.

Abstract: For the first time, the capacitive non-linearity is considered and calibrated. Based on the traditional bootstrapped switch, a cell is added to eliminate the first-order capacitive non-linearity. The measurement shows that the sampling and holding circuit using the improved bootstrapped switch can achieve a SFDR of 86dB with respect to 76dB for the traditional one.

Abstract: We fabricated and studied the electrical characteristics of thin-film transistors with an amorphous zinc-tin–oxide (a-ZTO) channel, which was deposited by radio frequency magnetron co-sputtering under different oxygen partial pressures. The effect of varying the oxygen concentration on the electrical properties and device performance of the a-ZTO TFTs was investigated. A positive shift observed in the threshold voltage with increasing oxygen suggests that the number of oxygen vacancies in the a-ZTO film decreased. With an oxygen flow rate of 4 %, a threshold voltage of 2.25 V, an on-off current ratio of 2.1 × 10³, and a subthreshold slope of 0.8 V·dec⁻¹ were obtained.