Threshold Voltage Shift Of MOSFETs Research Articles

Impact of Semiconductor Permittivity Reduction on Electrical Characteristics of Nanoscale MOSFETs

The dielectric screening property of a semiconductor is very crucial for the electrical characteristics of a MOSFET, and which can be described mathematically by Poisson equation via the permittivity. While the theory and experiments have corroborated the permittivity reduction of nanoscale Si, this paper studies the electrical characteristics of MOSFETs considering the reduced channel permittivity by quantum transport simulations. It is found that the channel permittivity reduction may mitigate the short-channel effects, showing subthreshold swing improvement and threshold voltage shift of MOSFETs in nanoscale. Compared to quantization effects, the positive and negative impacts of the channel permittivity reduction on the devices in particularly nanoscale have been investigated. This paper elucidates the necessity of considering semiconductor permittivity reduction for nanoscale device design and simulations.

Investigation of sensitivity and threshold voltage shift of commercial MOSFETs in gamma irradiation

This article is about the absorbed-dose-dependent threshold voltage shift of the MOSFET transistors. Performance of the MOSFETs has been tested in different gate voltages. Sensitivity of the transistors for 662 keV gamma ray is studied in 1–5 Gy dose range. It was found that for transistors irradiated in biased mode, significant changes in the threshold voltage occurred, and the sensitivity to gamma rays increased with the bias voltage.

Thick film SOI technology: characteristics of devices and performance of circuits for high-energy physics at cryogenic temperatures; effects of ionizing radiation

We report here the characteristics of elementary devices and circuits when they are exposed at low temperature (≈ 90 K) to ionizing radiation. These devices and circuits are implemented in a radiation-hardened SOI monolithic technology. We have made irradiations both at high dose rates (≈ 100 krads/h) and low dose rate (≈ 0.02 krad/h), the low dose rate is of the order of magnitude of the value which should be encountered in high-energy physics calorimeters during future experiments. A reduction of the dose rate, at identical total dose received, has a favourable effect on the threshold voltage shift of MOSFETs and, consequently, on the behaviour of circuits designed with these devices. For example, a preamplifer remained functional with no significant change in its characteristics (noise and rise time) after ≈ 100 krads irradiation during a longer than 6 months exposure at 90 K (liquid-argon temperature). This is of key importance for the future development of silicon microelectronics for Liquid-Argon Calorimetry.

Characterization, modeling, and minimization of transient threshold voltage shifts in MOSFETs

MOSFETs subjected to large-signal gate-source voltage pulses on microsecond to millisecond time scales exhibit transient threshold voltage shifts which relax over considerably longer periods of time. This problem is important in high-accuracy analog circuits where it can cause errors at the 12 b level and above. In this paper, transient threshold voltage shifts are characterized with respect to their dependence on stress amplitude and duration, relaxation time, gate bias, substrate bias, drain voltage, temperature, and channel width and length. In contrast to previous studies, threshold voltage shifts are measured at time and voltage scales relevant to analog circuits, and are shown to occur even when the effects of Fowler-Nordheim tunneling, avalanche injection, hot carriers, trap generation, self-heating, mobile ions, and dipolar polarizations are absent. A new model is proposed in which channel charge carriers tunnel to and from near-interface oxide traps by one of three parallel pathways. Transitions may occur elastically, by direct tunneling between the silicon band edges and an oxide trap, or inelastically, by tunneling in conjunction with a thermal transition in the insulator or at the Si-SiO/sub 2/ interface. Simulations based on this model show excellent agreement with experimental results. The threshold voltage shifts are also shown to be correlated with 1/f noise, in corroboration of the tunneling model. Techniques for the minimization and modeling of errors in circuits are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>