Florin Babarada

MOSFET simulation - TCAD tools/packages

Industry-standard TCAD software packages are widely used by semiconductor companies to optimise processes and devices in integrated circuits fabrication. After process and device simulation one can go ahead with circuit simulation using Spice. This paper focuses on the matching of these program packages in the area of parameter and characteristics extraction. We compared the transfer characteristics of n-type MOSFET, biased in the linear region, obtained from Synopsys package including TSUPREM4 and MEDICI with transfer characteristics from PSpice package.

THE ANALOG PROCESSING AND DIGITAL RECORDING OF ELECTROPHYSIOLOGICAL SIGNALS

The paper presents the aspects of design and implementation of a chain for electrophysiological signal recording, respectively collection, analog processing and digital data recording. The analog processing is based of dynamic range compressor circuit composed by the automatic gain control with a recovery delay to minimize the distortions, thermal behavior compensation and an adaptation stage for levelmeter. At compressor output was added a clipper, which must catch all the transitions, that escapes out of the dynamic range compressor and at clipper output a lowpass filter to cuts abruptly the high frequencies. The data vector recording is performing by strong internal resources microcontroller including ten bits A/D conversion port.

Simulation, design and microfabrication of multichannel microprobe for bioelectrical signals recording

The extracellular potential simultaneous recording permits the investigation of the central nervous activity. The paper presents the design and manufacturing steps of a five electrodes microprobe for recording the electrical activity of neural cells and tissues integrated on the same chip with the electronics. The specific fabrication processes of the integrated microprobe are presented. An implantable neural microprobe is going to be developed to enable the correlation between electrical activity in the human nervous system and externally psychoelectrical stimuli. The electronics accomplish the separation and reduction of the biological noise recording.

More Accurate Models Of The Interfaces Oxide Charge From The Ultra‐Thin SOI Films

An inherent SOI device dedicated for the in situ electrical characterization of wafers is the pseudo‐MOS transistor that easily provides a key parameter: Flat‐Band Voltage, VFB. Usual models for this voltage were established for SOI structures with 0,2μm…2μm film thickness and 0,4…100μm oxide thickness. The classical models of VFB, deduced for micronic sizes, present some deficiencies in the nanodevice area. An interface charge about 1012e/cm2 in micronic sizes means 1e/100nm2 equivalent with one electron per device area in the nano‐domain. This paper analyses the flat‐band voltage modeling, due to the consequences of the down‐scaling of the SOI wafers.

Electrophysiological Data Processing Using a Dynamic Range Compressor Coupled to a Ten Bits A/D Convertion Port

The paper presents a hardware solution of the in vivo electrophysiological signals processing, using a continuous data acquisition on PC. The originality of the paper comes from some blocks proposal, which selective amplify the bio signals. One of the major problems in the electrophysiological signals monitoring is the impossibility to record the weak signals from deep organs that are covered by noise or by strong cardiac or muscular signals. An automatic gain control block is used, so that the high power skin signals are less amplified than the low components. The analog processing block is based on a dynamic range compressor, containing the automatic gain control block. The following block is a clipper since to capture all the transitions that escape from the dynamic range compressor. At clipper output a low-pass filter is connected since to abruptly cut the high frequencies, like 50Hz, ECG. The data vector recording is performing by strong internal resources micro controller including ten bits A/D conversion port.

From simulations to masks for a BioFET design

This paper presents the TCAD techniques used for the simulation, optimisation and design of the BioFET device parameters, using a specialised software package, ATLAS. The values of these parameters will prescribe the process fabrication and device size. Using EDA tools like LEDIT, the layers that will constitute the fabrication masks for both active and reference devices will be established, as a first novelty of this paper. A biodevice description in Atlas program, including an enzyme within the gate space, represents a second original approach. Besides to the simulations and mask design, the paper exposes some comparative experimental results concerning a nanostructured material, suitable for the enzyme entrapping.

MOSFET distorsion analysis including series resistance modelling aspects

The new challenge of nanotechnology needs very accurate models for active devices. From this point of view the design of linear analog circuits lacks models for state-of-the-art MOS transistors to accurately describe distortion effects. This is mainly due to inaccurate modelling of the second order effects such as mobility degradation due to high vertical gate field, velocity saturation in the channel and short channel series resistance. After a rigorous description of series resistance components we included the series resistance in the MOS transistor model and used a compact expression of series resistance for computation reasons. The simulations using the new series resistance expression were in good agreement with experimental data.

MOSFET mobility degradation modelling

The design of linear analog circuits lacks models for state-of-the-art MOS transistors to accurately describe distortion effects. This is mainly due to inaccurate modelling of the mobility degradation effect i.e. the dependence of carrier mobility in the inversion layer on the normal electric (gate) field. A new mobility relation in agreement with experiment was obtained using quantum mechanical transport analysis.

Vertical variants of PIN and p-NOI tunnel electronic devices and potential applications

Communication traffic continue to improve due to the rapid growth in broadband access in recent years, frequently based on PIN or tunnel devices. The present paper discuses two kind of tunnel devices, in a vertical configuration through the cross-section, allowing the tunnel current flow from upper anode to bottom cathode: PIN and NOI device in a planar technology (p-NOI). Recently, the NOI — Nothing On Insulator device was proposed and timely updated. It belongs to a vacuum nano-transistor class. The simulations reveal few better device parameters versus related devices from literature. The vertical p-NOI device with a dual MOS gated diode configuration, overpass the fabricated vacuum nanotransistors with SS=0.4V/dec << SS=4.1V/dec. The PIN vertical diode with three compensated drift regions offers higher breakdown voltage, keeping the forward series resistance as low as possible. Finally, the applications of the PIN and NOI devices are presented.

Fast fluorescence detection in optical bio-systems

In order to detect the fluorescence on biological sample still exist extremely elegant solutions that involve high technology of high equipment costs, rather suitable for biomarker discovery in research than routine clinical tests in a very short time. In this scope, we present a fast real-time application that is running on mobile phones with included optical acquisition system. From the main menu where the application can be configured, as number of samples, colour depth of the camera and picture resolution, all features are automatically filled after a picture is loaded. After the sample selection, some options as re-crop for wrong sample or as start processing will automatically compute the histograms, determine the fluorescence intensity from them, interpolate the logistic curve and show the measured parameters that define the image.