Silicon-on-insulator Field-effect Transistor Research Articles

Single-Charge Tunneling in Codoped Silicon Nanodevices.

Silicon (Si) nano-electronics is advancing towards the end of the Moore's Law, as gate lengths of just a few nanometers have been already reported in state-of-the-art transistors. In the nanostructures that act as channels in transistors or depletion layers in pn diodes, the role of dopants becomes critical, since the transport properties depend on a small number of dopants and/or on their random distribution. Here, we present the possibility of single-charge tunneling in codoped Si nanodevices formed in silicon-on-insulator films, in which both phosphorus (P) donors and boron (B) acceptors are introduced intentionally. For highly doped pn diodes, we report band-to-band tunneling (BTBT) via energy states in the depletion layer. These energy states can be ascribed to quantum dots (QDs) formed by the random distribution of donors and acceptors in such a depletion layer. For nanoscale silicon-on-insulator field-effect transistors (SOI-FETs) doped heavily with P-donors and also counter-doped with B-acceptors, we report current peaks and Coulomb diamonds. These features are ascribed to single-electron tunneling (SET) via QDs in the codoped nanoscale channels. These reports provide new insights for utilizing codoped silicon nanostructures for fundamental applications, in which the interplay between donors and acceptors can enhance the functionalities of the devices.

Solution pH Effect on Drain-Gate Characteristics of SOI FET Biosensor

Nanowire or nanobelt sensors based on silicon-on-insulator field-effect transistors (SOI-FETs) are one of the leading directions of label-free biosensors. An essential issue in this device construction type is obtaining reproducible results from electrochemical measurements. It is affected by many factors, including the measuring solution and the design parameters of the sensor. The biosensor surface should be charged minimally for the highest sensitivity and maximum effect from interaction with other charged molecules. Therefore, the pH value should be chosen so that the surface has a minimum charge. Here, we studied the SOI-FET sensor containing 12 nanobelt elements concatenated on a single substrate. Two types of sensing elements of similar design and different widths (0.2 or 3 μm) were located in the chips. The drain-gate measurements of wires with a width of 3 µm are sufficiently reproducible for the entire chip to obtain measurement statistics in air and deionized water. For the pH values from 3 to 12, we found significant changes in source-drain characteristics of nanobelts, which reach the plateau at pH values of 7 and higher. High pH sensitivity (ca. 1500 and 970 mV/pH) was observed in sensors of 3 μm and 0.2 μm in width in the range of pH values from 3 to 7. We found a higher “on” current to “off” current ratio for wide wires. At all studied pH values, Ion/Ioff was up to 4600 and 30,800 for 0.2 and 3 μm wires, respectively. In the scheme on the source-drain current measurements at fixed gate voltages, the highest sensitivity to the pH changes reaches a gate voltage of 13 and 19 V for 0.2 μm and 3 μm sensors, respectively. In summary, the most suitable is 3 μm nanobelt sensing elements for the reliable analysis of biomolecules and measurements at pH over 7.

A Neuro-Space Mapping Method for Harmonic Interference Prediction of SOIFET Radio Frequency Switches

With the rapid development of wireless communication, the requirements of high-integration and low-cost radio frequency (RF) front-end modules in mobile phones result in more usage of silicon-on-insulator field effect transistors (SOIFETs) for the manufacturing of RF switches. However, the nonlinear behavior of SOIFET switches in <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> -state always produces unwanted harmonics distortion interference when they are excited by a large signal. In this article, we simplify the well-known physics-based surface potential model to an interelectrode nonlinear capacitance (INC) model since it adequately describes the harmonic effects produced by the transistor. The INC model, referred to as the coarse model, cannot match the behavior of the real switch, since many parameters of the switch cannot be accurately determined. This article proposes a novel dynamic neuro-space mapping network model, referred to as the fine model, to optimize the INC model. The proposed model takes advantage of the high accuracy of the fine model and the fast speed of the coarse model. Ultimately, the proposed method can accurately predict the harmonics interference for SOIFET switches in the complex RF front-end environment and provides an intuitive guideline under the design stage to prevent EMI problems.

SOI-FET Snsors for Virus Detection

The recent outbreak of coronavirus disease caused by the respiratory syndrome coronavirus 2 (SARS-CoV-2) has highlighted the urgent need to develop fast and highly sensitive analytical tools and diagnostic devices to detect and study of the fundamental properties viruses and their nucleic acid and protein components [1]. Silicon-on-insulator field-effect transistors (SOI-FETs) based sensors provide the versatile platform for direct detection of biological species as excellent electrical signal converters. These devices have demonstrated applications for label-free, ultra-sensitive, and selective real-time detection of a wide range of biological species, including nucleic acids, proteins and viruses in either single-element or multiplexed formats [2-5]. Dielectrophoresis (DEP) and electro-hydrodynamic techniques are well known as the methods of selection and delivery of analytes to overcome limitations of diffusive transport to sensor elements without additional processing or labeling steps [6].The aim of this study was to investigate the features of the behavior of the viruses when they are indicated by SOI-FET sensors with DEF-control. For this, SOI-FET sensors with lateral DEP-electrodes and multichannel sensors, for comparison, were used. Top-down technology with using optical lithography was applied for sensor fabrication. Devices manufacturing details are described elsewhere [3]. As an analyte, we used nuclear polyhedrosis viruses (NPVs), coronavirus virus-like particles (CVP) and suspension of specific antibodies to the virus created in the Federal research center of Virology and biotechnology "Vector" of Rospotrebnadzor.The results showed that the sensors used in the study provide the subatomolar level of virus detection. DEP-concentration of viruses increase the response of the sensors by factors of 2 to 9 (compared to the response of sensors without DEP control) and allows the false positives can be eliminated. NPVs lose their mobility with prolonged exposure to an alternating field in the sub-MHz range. The DEP-concentration of CVP leads to the formation of crystal-like structures (Fig.1).This study was supported by grant no. 18-29-02091 of the Russian Foundation for Basic Research. Sample preparation of biological materials was done within the framework of the State Task of Rospotrebnadzor.Referencies: WHO Director-General's opening remarks at the media briefing on COVID-19 – 23 April 2021 23 апреля 2021 г.https://www.who.int/director-general/speeches/detail/who-director-general-s-opening-remarks-at-the-media-briefing-on-covid-19-23-april-2021.Patolsky F., Zheng G., Hayden O., Lakadamyali M., Zhuang X., Lieber C. M. Electrical detection of single viruses // Proc. Natl. Acad. Sci. 2004, v. 101. p. 14017-14022.O. V. Naumova, V. M. Generalov, E. G. Zaitseva, A. V. Latyshev, A. L. Aseev, S. A. Pyankov, I. V. Kolosov, G. G. Ananko, A. P. Agafonov, E. V. Gavrilova, R. A. Maksyutov, and A. S. Safatov. Biosensors Based on Soi Nanowire Transistors for Biomedicine and Virusology. Russian Microelectronics, 2021, v. 50, N3, p. 137–145.Ivanov Y.D., Pleshakova T.O., Kozlov A.F., Malsagova K.A., Krohin N.V., Shumyantseva V.V., Shumov I.D., Popov V.P., Naumova O.V., Fomin B.I., Nasimov D.A., Aseev A.L., Archakov A.I. SOI nanowire for the high-sensitive detection of HBsAg and a-fetoprotein. Lab Chip. 2012, v. 12, p. 5104-5111.Dmitrienko E., Naumova O., Fomin B., Kupryushkin M., Volkova A., Amirkhanov N., Semenov D., Pyshnaya I., Pyshnyi D. Surface modification of SOI FET sensors for label-free and specific detection of short RNA analyte. Nanomedicine 2016, v. 11, N 16, p. 2073-2082.Lee S., Roh S.M., Lee E., Park Y., Lee B.C., Kwon Y., Kim H.J., Kim J. Applications of converged various forces for detection of biomolecules and novelty of dielectrophoretic force in the applications(Review). Sensors, 2020, v.20, p.3242. Fig.1 – Optical image of sensor with lateral DEP electrodes after CVP detection. In the left - CVP organized in crystal-like structures under DEP-concentration, in the right (green dots on dark field) - viruses with luminescent labels. S - source, D - drain. G1, G2 - lateral DEP electrodes. Figure 1

Investigation of capacitor-less integrate and fire neuron by using dual-gate a PN-body tied silicon on insulator field-effect transistor

In this study, integrate and fire neuron by using a dual-gate (DG) PN-body tied (PNBT) silicon on insulator field-effect transistor (SOI-FET) was investigated. We found out that the DG PNBT SOI-FET has the integrate and fire function in a single device. The floating body and the positive feedback effect can perform the functions of the capacitor and comparator, respectively. The device can generate a continuous spike and also a single spike signal with the additional reset scheme. The reset action requires a recovery time, which can be controlled by voltage conditions. It has a chance of making a refractory period function. These characteristics mean that it is possible to realize the capacitor-less small footprint neuron circuit with the DG PNBT SOI-FET.

P-Channel and N-Channel Super-Steep Subthreshold Slope PN-Body Tied SOI-FET for Ultralow Power CMOS

In this paper, n-channel and p-channel super-steep subthreshold slope (SS) PN-body tied (PNBT) silicon on insulator field-effect transistors (SOI-FETs) are demonstrated. The PNBT structure has a symmetrical source and drain structure. The devices show super-steep SS (< 1 mV/dec) characteristics while maintaining low off current (< 1 pA/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$ </tex-math></inline-formula> m) and high on/off ratio (up to 6 decades) with low drain voltage (Vd = ± 0.1 V), good output characteristics, and threshold voltage controllability. The devices have a body current and a hysteresis characteristic; however, these can be suppressed under proper device conditions. The operation mechanism of the PNBT SOI-FET is clarified by simulation, and an inherent thyristor on the PNBT structure plays a significant role. Both the p-channel and n-channel PNBT SOI-FET characteristics are discussed, and it is indicated that an ultralow power complementary metal-oxide-semiconductor can be realized by the PNBT SOI-FET.

Fabrication, Characterization, and Modeling of Field-Effect-Transistor Nanoribbon Biosensors

For over 30 years, field effect transistors (FETs) have been used as sensors. In the past, Ion-Sensitive-FETs (ISFET) were based on bulk Metal-Oxide-Semiconductor (MOS) FET designs and the device was gated by biasing the electrolyte through the reference electrode. Recently, functionalized silicon nanowires and silicon-on-insulator (SOI) devices have been introduced for their greater sensitivity in detecting proteins, DNA and even single viruses.This work reviews a variety of issues that impact the properties of SOI FET nanoribbon sensors.1-7 The ability to stabilize and control the attachment of cells on the sensor surface is critical. Therefore, the reliability and reproducibility of self-assembled-monolayers such as aminosilanes will be presented. Biological solutions consist of protein or DNA in an electrolytic solution containing salt ions. Some of these ions, such as Na, have long been known to cause instabilities in MOS devices. The effect of mobile ions on SOI-based sensors will be presented. The SOI-based sensor structure results in the electrolyte voltage being capacitively coupled to the back gate voltage. The impact of this coupling on sensor response will be described. Physically realistic SPICE models were developed and illustrate the response of both pH and biosensors with a multi-gate model. The model demonstrates good agreement to experimental data including the impact of Debye screening and site binding charge. The benefits and use of novel 2D semiconductors for biosensing will also be described.ACKNOWLEDGMENTSThe author would like to acknowledge the previous and current researchers who contributed to this work including: P. G. Fernandes, K. D. Cantley, G. A. Mahmud, A. Tarasov, M. Y. Tsai, O. Seitz, R. Tian, N. Karnik, H. Stiegler, R. A. Chapman, and Y. J. Chabal. The author would also like to acknowledge the support of NSF CBET Award #1264705, the SRC Texas Analog Center of Excellence, and Texas Instruments.REFERENCESP. G. Fernandes, R. A. Chapman, O. Seitz, H. J. Stiegler, H. C. Wen, Y. J. Chabal, and E. M. Vogel, IEEE Electron Device Letters 33, 447-449 (2012).P. G. Fernandes, H. J. Stiegler, B. Obradovic, R. A. Chapman, H.-C. Wen and E. M. Vogel, Sensors and Actuators B 161, 163-170 (2012).K. D. Cantley, P. G. Fernandes, M. Y. Zhao, H. J. Stiegler, R. A. Chapman, in Midwest Symposium on Circuits and Systems Conference Proceedings, 370-373 (2012).O. Seitz, P. G. Fernandes, G. Mahmud, H. –C. Wen, H. J. Stiegler, R. A. Chapman, E. M. Vogel, Y. J. Chabal, Langmiur 27, 7337-7340 (2011).R. A. Chapman, Fellow, P. G. Fernandes, O. Seitz, H. J. Stiegler, H.-C. Wen, Y. J. Chabal, and E. M. Vogel, IEEE Transactions on Electron Devices 58, 1752-1660 (2011).O. Seitz, P. G. Fernandes, R. Tian, N. Karnik, H.-C. Wen, H. Stiegler, R. A. Chapman, E. M. Vogel and Y. J. Chabal, Journal of Materials Chemistry 21, 4384-4392 (2011).P. G. Fernandes, O. Seitz, R. A. Chapman, H. J. Stiegler, H.-C. Wen, Y. J. Chabal, and E. M. Vogel, Applied Physics Letters 97, 034103 (2010).

Thin Layer SOI-FETs Used for Stress-Sensing and Its Application in Accelerometers

In this paper, double-clamped beam with a mass at the center has been fabricated on substrate of a Silicon-on-Insulator (SOI) wafer. Thin layer SOI Field-Effect Transistors (SOI-FETs) have been integrated at ends of the beam on top layer of the SOI wafer, which can be used for stress-sensing. Such a structure can be used as an accelerometer. The applied acceleration can be detected directly by the changing of the drain current. The measured sensitivity and noise floor of the device are 0.91 mV/g and 13 mg/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1/2</sup> . As expected performance of the SOI-FETs, such an accelerometer can be used in a wide temperature range (-60°C to 200°C) in some special applications, such as military, automobile, nuclear and well-logging industry application. Note to Practitioners - This paper describes the method for stress-sensing using the thin layer Silicon-on-Insulator Field-Effect Transistors (SOI-FETs). This method is characterized with adjustable sensitivity and wide working temperature range and is expected to apply in strain gauges, pressure sensors, accelerometers, and cantilever force/displacement sensors. In the paper we take the application in accelerometers for example. A structure of double-clamped beam with a mass at the center has been fabricated on the substrate of a SOI wafer. Based on the devices, we have measured the characteristics of the sensitivity, the noise floor and the working temperature, which is critical in some applications such as military, automobile, nuclear, and well-logging industry application.

Physical Model of the Junctionless UTB SOI-FET

In this paper, we model the electrical properties of a junctionless (JL) ultrathin-body silicon-on-insulator field-effect transistor (SOI-FET), which has been proposed as a possible alternative to the junction-based SOI-FET. The model is based on improved depletion approximation, which provides a very accurate solution of Poisson's equation and allows for the computation of the substrate, as well as the Si-body lower- and upper-surface potentials by an iterative procedure, which accounts for the back-oxide (BOX) charge and thickness and the potential drop within the substrate. The drain current is then computed versus gate, drain, and substrate voltages via integral expression and validated by comparison with technology computer-aided design simulation results. Analytical models of the field-effect-transistor threshold voltage and subthreshold slope are worked out against the substrate voltage, highlighting the effect of the substrate doping and BOX thickness on the aforementioned parameters. In essence, this work provides the physical background for better understanding of the JL SOI-FET and its assessment for logic applications.

KFM Observation of Electron Charging and Discharging in Phosphorus-Doped SOI Channel

Low temperature Kelvin Probe Force Microscopy (LT-KFM) can be used to monitor the electronic potential of individual dopants under an electric field. This capability is demonstrated for silicon-on-insulator field-effect-transistors (SOI-FETs) with a phosphorus-doped channel. We show results of the detection of individual dopants in Si by LT-KFM. Furthermore, we also observe single-electron charging in individual dopants located in the Si channel region.

Controlling properties of field effect transistors by intermolecular cross-linking of molecular dipoles

In this study, we show that systematic molecular control over a silicon-on-insulator field effect transistor (SOI-FET) device can be achieved by controlling the Si–O–Si intermolecular interactions between adjacent trichlorosilane molecules. This is attributed to the fact that Si–O–Si intermolecular bonds between the parallel molecular dipoles change the overall charge distribution within the organic layer, and, consequently, alter the channel surface potential. Changes in the potential within the formed monolayer close to the channel alter the source-drain current and, consequently, the transistor threshold (turn on) voltage.

Prediction and Measurement of Temperature Fields in Silicon-on-Insulator Electronic Circuits

Field-effect transistors (FETs) in conventional electronic circuits are in contact with the high-thermal-conductivity substrate. In contrast, FETs in novel silicon-on-insulator (SOI) circuits are separated from the substrate by a thermally resistive silicon-dioxide layer. The layer improves the electrical performance of SOI circuits. But it impedes conduction cooling of transistors and interconnects, degrading circuit reliability. This work develops a technique for measuring the channel temperature of SOI FETs. Data agree well with the predictions of an analytical thermal model. The channel and interconnect temperatures depend strongly on the device and silicon-dioxide layer thicknesses and the channel–interconnect separation. This research facilitates the thermal design of SOI FETs to improve circuit figures of merit, e.g., the median time to failure (MTF) of FET–interconnect contacts.