Emerging nanoelectronics device design exploration incorporating vertical impact-ionization mosfet and strained (SiGe) technology

Miniaturization of semiconductor devices beyond sub-lO0nm has commenced several problems for further scaling. Low subthreshold voltage, reduced carrier mobility, and increased leakage currents were identified to be the paramount issues that leads to high power consumption and heating. The Impact Ionization MOSFET (IMOS) device has evolved to attract increasing attention for its ability to overcome these problems. The IMOS device works on the principle of avalanche breakdown mechanism that gives very good subthreshold slopes of 20mV/decade, but at high supply voltage. Hence, to bring down the supply voltage as well as to obtain low threshold voltage and subthreshold voltage, the Vertical Strained Silicon Germanium (SiGe) Impact Ionization MOSFET (VESIMOS) has been successfully developed in this study. VESIMOS device integrates vertical structure concept of IMOS and strained SiGe technology. The VESIMOS has been designed and simulated using Silvaco Technology Computer Aided Design (TCAD) tools for both device process {ATHENA) and characterization (ATLAS) respectively. The transfer characteristics of VESIMOS showed an inverse proportionality of supply voltage and subthreshold voltage due to lower breakdown strength of Ge content. However, the subthreshold voltage is in direct proportion to the leakage current. The subthreshold voltage, S=l0mV/dec was obtained at threshold voltage, VTH=0.9V, with supply voltage, Vo5=1.75V. This VTH was found to be 40% lower than the Si-vertical IMOS device's VTH, The output characteristics of VESIMOS found that the device goes into saturation for supply voltage more than 2.SV, attributed to the presence of Germanium (Ge) that has high and symmetric impact ionization rates. In addition, VESIMOS electron mobility was found to be improved by 40% compared to Si-vertical IMOS, due to the presence of the compressive strain. Consequently, it is also revealed that an increase in strain will also increase mobility and reduce further the threshold voltage. However, the increase in strain layer thickness {T SIGe), resulted in an increase of threshold voltage and lowered the mobility. This is due to the strain relaxation in the SiGe layer. In addition, it is also found that at high source-drain doping concentration (S/D=2x1018/cm3), the threshold voltage dropped to 0.88V, with supply voltage of 1.75V. This is due to high electric field effect in the channel at high doping concentration, which is contrary to the doping effects of conventional MOSFET

Comparison analysis on scaling the vertical and lateral NMOSFET in nanometer regime

Conventional lateral and vertical n-channel MOS transistors with channel length in the range of 100 nm to 50 nm have been systematically investigated by means of device simulation. The comparison analysis includes critical parameters that govern device performance. Threshold voltage VT roll-off, leakage current Ioff drain saturation current IDsat and sub-threshold swing S were analyze and compared between the device. Due to double gate (DG) structure over the side of silicon pillar a better electrostatics potential control of channel is obtained in vertical device shown by an analysis on VT roll-off. A two decade higher of Ioff in planar device is observed with Lg = 50 nm. A factor of three times larger IDsat is observed for vertical MOSFETs compared to planar device. The sub-threshold swing S remains almost the same when the Lg larger than 80 nm. It increased rapidly when the Lg is scaled down to 50 nm due to the short channel effect SCE. However, the vertical device has a steady increase whereas the planar device has suffered immediate enhance of SCE. The analysis results confirmed that vertical MOSFET with double-gate structure is a potential solution to overcome SCE when scaled the channel length to 50 nm and beyond

Smart Grid Security: Threats, Challenges, and Solutions

The cyber-physical nature of the smart grid has rendered it vulnerable to a multitude of attacks that can occur at its communication, networking, and physical entry points. Such cyber-physical attacks can have detrimental effects on the operation of the grid as exemplified by the recent attack which caused a blackout of the Ukranian power grid. Thus, to properly secure the smart grid, it is of utmost importance to: a) understand its underlying vulnerabilities and associated threats, b) quantify their effects, and c) devise appropriate security solutions. In this paper, the key threats targeting the smart grid are first exposed while assessing their effects on the operation and stability of the grid. Then, the challenges involved in understanding these attacks and devising defense strategies against them are identified. Potential solution approaches that can help mitigate these threats are then discussed. Last, a number of mathematical tools that can help in analyzing and implementing security solutions are introduced. As such, this paper will provide the first comprehensive overview on smart grid security

INVESTIGATION OF SHORT CHANNEL EFFECT ON VERTICAL STRUCTURES IN NANOSCALE MOSFET

The recent development of MOSFET demands innovative approach to maintain the scaling into nanoscale dimension. This paper focuses on the physical nature of vertical MOSFET in nanoscale regime. Vertical structure is one of the promising devices in further scaling, with relaxed-lithography feature in the manufacture. The comparison of vertical and lateral MOSFET performance for nanoscale channel length (Lch) is demonstrated with the help of numerical tools. The evaluation of short channel effect (SCE) parameters, i.e. threshold voltage roll-off, subthreshold swing (SS), drain induced barrier lowering (DIBL) and leakage current shows the considerable advantages as well as its thread-off in implementing the structure, in particular for nanoscale regime

Effect of seaweed physical condition for biogas production in an anaerobic digester

The increasing demand for environmental protection and renewable energy has made bioenergy technologies such as anaerobic digestion substantially attractive. The main objective of this study is to determine the biogas yield from the raw seaweed Eucheuma cottonii and waste products using anaerobic digestion, operated under different physical conditions. Seaweeds comprise of a thallus (leaf like) and sometimes a stem and a foot (holdfast). Seaweed has the potential to be developed into the raw and waste material for biogas due to higher growth rates, greater production yields, and higher carbon fixation rates than land crops. Seaweed has 4–39% carbohydrate content and a high moisture content with low lignin compared to other terrestrial plants, thus it is simpler to be degraded. The integration of the findings may be the key to make seaweed waste product that is more efficient and affordable to serve as a sustainable and renewable energy source. The study used 1.5,L anaerobic digesters for fresh and 3-month-old Eucheuma sp. evaluated at different stages by monitoring the pH, chemical oxygen demand, and biogas production. The study found that within 18,days, the anaerobic digestion of E. cottonii seaweed yielded 0.4–1 ml biogas/g seaweed with up to 56% methane content

Emergency medical services: Safety awareness between teaching and public hospital

Increased in demand from the public for a better Emergency Medical Services (EMS) have alert the Malaysia Ministry of Health to increase the quality of this services as it act as a front line.Emergency medical provider deals with any patient from their homes and street to the hospital door in pre-hospital care, from the non-critical to the most critical cases in the department, and for society from all strata of life.In order to give the best service and as a front line medical provider, acquiring a very good safety culture in the workplace is important so that they can serve and give the best services to the patient.The purpose of this article is to identify the safety awareness in workplace between teaching and public hospital at emergency medical services provider.This paper also offers a review of work culture in EMS as a front line of the medical services.Results of the survey later will be explained by the statistic provided.This will serve as a guideline for emergency medical provider on the knowledge about the importance of safety awareness at the workplace

Monolithic integration of tunable aperture and lens for distance sensor

A tunable aperture and lens are monolithically fabricated in wafer-level. The tunable aperture inserted in a camera can estimate distance as comparing blur of images by two different size apertures. We design optical system and integrate tunable aperture and first lens of camera. The plano-concave lens is fabricated by anodic bonding and thermal reflow under atmospheric pressure with one mask. The silicon substrate is used as spacer between tunable aperture and lens. Another glass substrate is attached to the silicon substrate by triple anodic bonding for tunable aperture operated by liquid crystal. The lens has diameter of 4.5 mm and sag height of 566 um and the tunable aperture has f-numbers of 1.8 and 4.0. This fabrication can control parameter of lens easily. Also, it can reduce error by alignment and gap among apertures and lenses. This distance sensor can be applied to the Advanced Driver Assistance System (ADAS)