Commercial Metal-oxide Semiconductor Field-effect Transistors Research Articles

Mechanisms of negative bias instability of commercial SiC MOSFETs observed by current transients

This article explains the mechanisms of negative bias instability in commercial n-channel SiC metal–oxide semiconductor field-effect transistors (MOSFETs) by analysis of transient gate currents. The current–voltage measurements were performed at different temperatures along with capacitance–voltage measurements to characterise hole trapping and de-trapping in planar SiC MOSFETs. The experimental results reveal that near-interface traps (NITs) with energy levels aligned to the valence band trap holes from the valence band by tunneling, which is different from published results about NITs with energy levels aligned to the energy gap. The impact of the aluminium implantation process of the p-type region on hole trapping is also demonstrated. The presented analysis also reveals that the hole trapping by NITs is limited to the p-type region, indicating that the aluminium implantation process is responsible for the detected NITs.

Review on the Reliability Mechanisms of SiC Power MOSFETs: A Comparison Between Planar-Gate and Trench-Gate Structures

To clarify the current research situation and offer a better understanding of the reliability for silicon carbide (SiC) power metal-oxide-semiconductor field-effect transistors (MOSFETs), a comparison among the reliability mechanisms between planar-gate and trench-gate SiC power MOSFETs, which have not been comprehensively summarized, is made in this work. The latest studies focusing on the reliability issues of commercial SiC MOSFET products, including the planar-gate device, the double-trench device and the asymmetric trench-gate device, are reviewed. For the existing of the gate trenches and the unique structures protecting them, SiC trench-gate MOSFETs express quite different instability phenomena from the planar-gate ones under various ultimate and long-term electro-thermal stresses. The influences of these stresses closely related to the practical operation conditions on SiC power MOSFETs, including the avalanche stress, the short-circuit (SC) stress, the surge current stress of the body diode, and the switching stress, are discussed and reviewed in details.

Comparison of the Performance-Degrading Near-Interface Traps in Commercial SiC MOSFETs

This paper presents a comparison of the density of performance-degrading near-interface traps (NITs) in the most commonly available 1200 V commercial N-channel SiC power metal–oxide–semiconductor field-effect transistors (MOSFETs). A recently developed integrated-charge technique was used to measure the density of NITs with energy levels aligned to the conduction band, which degrade MOSFET’s performance by capturing and releasing electrons from the channel biased in the strong-inversion condition. Trench MOSFETs of one manufacturer have lower densities of these NITs in comparison to MOSFETs with the planar gate structure, corresponding to observed higher channel-carrier mobility in trench MOSFETs. Different response-time distributions were also observed, corresponding to different spatial location of the measured NITs.

Positive-to-negative subthreshold swing of a MOSFET tuned by the ferroelectric switching dynamics of BiFeO3

Ferroelectricity can reduce the subthreshold swing (SS) of metal-oxide-semiconductor field-effect transistors (MOSFETs) to below the room-temperature Boltzmann limit of ~60 mV/dec and provides an important strategy to achieve a steeper SS. Surprisingly, by carefully tuning the polarization switching dynamics of BiFeO3 ferroelectric capacitors the SS of a commercial power MOSFET can even be tuned to zero or a negative value, i.e., the drain current increases with a constant or decreasing gate voltage. In particular, in addition to the positive SS of lower than 60 mV/dec, the zero and negative SS can be established with a drain current spanning for over seven orders of magnitude. These intriguing phenomena are explained by the ferroelectric polarization switching dynamics, which change the charge redistributions and accordingly affect the voltage drops across the ferroelectric capacitor and MOSFET. This study provides deep insights into understanding the steep SS in ferroelectric MOSFETs, which could be promising for designing advanced MOSFETs with an ultralow and tunable SS.

The spatial and energy distribution of oxide trap responsible for 1/f noise in 4H-SiC MOSFETs

Low-frequency noise is one of the important characteristics of 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) that is susceptible to oxide traps. Drain-source voltage noise models of 4H-SiC MOSFETs under low–drain-voltage and inverse condition were proposed by considering the spatial and energy non-uniform distribution of the oxide trap, based on the McWhoter model for uniform trap distribution. This study performed noise experiments on commercial 4H-SiC MOSFETs, and revealed that the non-uniform spatial and non-uniform energy distribution caused new 1/f noise phenomenon, different from that under uniform spatial and energy distribution. By combining experimental data and theoretical models, the spatial and energy distribution of oxide traps of these samples were determined.

Time-Dependent Dielectric Breakdown of Commercial 1.2 kV 4H-SiC Power MOSFETs

Constant-voltage time-dependent dielectric breakdown (TDDB) measurements are performed on recently manufactured commercial 1.2 kV 4H-SiC power metal-oxide-semiconductor (MOS) field-effect transistors (MOSFETs) from three vendors. Abrupt changes of the electric field acceleration parameters ( γ) are observed at oxide electric fields ( E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ox</sub> ) around 8.5 MV/cm to 9 MV/cm for all commercial MOSFETs. Gate leakage currents and threshold voltage shifts are also monitored under different oxide fields ( E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ox</sub> = 8 MV/cm and 10 MV/cm). The results suggest the failure mode under high oxide electric field is modified by impact ionization or Anode Hole Injection (AHI) induced hole trapping. This observation agrees with previously published oxide reliability studies on SiC MOSFETs and suggests that constant-voltage TDDB measurements need to be carefully performed under low oxide fields to avoid lifetime overestimation caused by hole trapping. The extrapolated t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">63%</sub> lifetimes (times to 63% failures) from TDDB measurements performed at E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ox</sub> <; 8.5 MV/cm are longer than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> hours at 150°C for all vendors. The predicted lifetimes at E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ox</sub> = 4 MV/cm demonstrate more than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> times increases than the oxide lifetimes reported a decade ago, showing promising progress in SiC technology.

Antibodies fragments as enablers of cardiac troponin (cTn) detection with extended gate metal-oxide-semiconductor field effect transistors (EGFET)

Abstract Background Cardiac troponin is the gold standard biomarker used to rule in or out acute myocardial infarction (AMI) in patients. Highly sensitive and reliable detection mechanisms for this important biomarker are required for advancing the field of early detection in medical applications. Field effect transistor (FET) sensors, specifically functionalised with troponin antibodies, can perform specific detection of cardiac troponin I or T, with high sensitivity and low limit of detection (LoD), in fully scalable and low power operated intelligent sensing systems. Purpose To design and realize a new wearable blood or sweat on-chip sensor, able to perform a real-time reliable detection of the cardiac troponin level in a patient suffering of AMI symptoms or during the post-operative phase. The sensor exploits the voltammetric detection of biomarkers, and offers the potential for miniaturization and reduced hospitalization costs. Methods Electrical current modulation in field effect transistor-based sensors is used as transducing principle, as a result of the surface potential change following exposure to biological fluids containing different concentrations of antigens. The use of antibodies fragments, properly attached to the sensor surface, enhances the sensitivity. Proof of concept tests involve the detection of fluorescein. Results The specific antigen detection by means of an electrical measurement has been proved, with a detection limit of &amp;lt;1 nM (24ng/mL), linear range over one decade and a sensitivity around 70mV/decade. Fluorescein antibodies fragments, commercially purchased, were attached to the gate of an EGFET device; the binding events between fluorescein molecules and the correspondent antibodies modify the electrical conduction properties of the transducer, creating a current shift whose amplitude is univocally related to the antigen concentration. The exploitation of the antibodies fragments allows the antigens to bind closer to the sensing surface, creating a more noticeable electrical perturbation. The device is made of a commercial Metal Oxide Semiconductor FET (MOSFET), whose gate is extended by a platinum electrode for sensing. The metal is then functionalised by attaching covalently antibodies fragments that act as probes for the antigens in the tested biofluids. Laboratory samples were prepared in house, using fluorescein as antigen. Concentrations between 45pM and 1uM have been tested, and the absence of non-specific binding has been successfully proved with bovine serum albumin (BSA), for which any noticeable response has been recorded. Conclusion We report an important step towards a real-time and reliable detection of cardiac troponin by means of nano-ISFETs, demonstrating the fluorescein antigens-antibodies specific binding. Further steps consists in correctly achieve a surface functionalisation with cardiac troponin I antibodies, and further enhance the sensor LoD. Antigens detection with EGFET Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Swiss National Science Foundation: ERA-NET, FLAG-ERA CONVERGENCE

Review and analysis of SiC MOSFETs’ ruggedness and reliability

SiC MOSFETs (silicon carbide metal-oxide semiconductor field-effect transistors) are replacing Si insulated gate bipolar transistors in many power conversion applications due to their superior performance. However, ruggedness and reliability of SiC MOSFETs are still big concern for their widespread applications in the market, especially in safety-critical applications. The objective of this study is to provide a comprehensive picture on the ruggedness and reliability of commercial SiC MOSFETs, discover their failure or degradation mechanism, and propose some possible mitigation methods through both literature survey and in-depth analysis. The ruggedness of SiC MOSFETs discussed here includes short-circuit (SC) ruggedness, avalanche ruggedness, and their failure mechanism. The reliability issues include gate oxide reliability, degradation under high-temperature bias stress, repetitive SC stress, avalanche stress, power cycling stress, body diode's surge current stress, and their degradation mechanism. Furthermore, this study discusses methods and solutions to improve their ruggedness and reliability.

Simulation study of single event effects sensitivity on commercial power MOSFET with single heavy ion radiation

High-frequency semiconductor devices are key components for advanced power electronic system that require fast switching speed. Power Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is the most famous electronic device that are used in much power electronic system. However, the application such as space borne, military and communication system needs Power MOSFET to withstand in radiation environments. This is very challenging for the engineer to develop a device that continuously operated without changing its electrical behavior due to radiation. Therefore, the main objective of this study is to investigate the Single Event Effect (SEE) sensitivity by using Heavy Ion Radiation on the commercial Power MOSFET. A simulation study using Sentaurus Synopsys TCAD software for process simulation and device simulation was done. The simulation results reveal that single heavy ion radiation has affected the device structure and fluctuate the I-V characteristic of commercial Power MOSFET.

Effect of Gate-Oxide Degradation on Electrical Parameters of Power MOSFETs

Gate oxide in power metal–oxide–semiconductor field effect transistors (MOSFETs) degrades over time. The degradation leads to an accumulation of oxide-trapped charges within the gate oxide and an accumulation of interface-trapped charges at the oxide–semiconductor surface of power MOSFETs. Overtime, such charges significantly alter the electrical parameters of power MOSFETs; to observe this, the electrical parameters are utilized as precursors of gate-oxide degradation. The purpose of this paper is threefold: 1) to propose a new online precursor of gate-oxide degradation—the gate plateau time; 2) to demonstrate a simultaneous dip-and-rebound variation pattern of four precursors of gate-oxide degradation: threshold voltage, gate plateau voltage, gate plateau time, and on-resistance; and 3) to compare the shift tendencies of each precursor over the course of gate-oxide degradation. The existing studies of gate-oxide degradation mechanisms and their effects on threshold voltage and mobility reduction were extended to correlate a variation of all four precursors using analytical expressions. The variation patterns were experimentally verified using high-electric field stressing in two different commercial power MOSFETs. The new precursor, the gate plateau time, was found to be a competitive gate-oxide degradation precursor, as it had a higher positive shift than threshold voltage and gate plateau voltage. In addition, the threshold voltage was found to be the most sensitive indicator of the negative shift (dip), while the on-resistance and gate plateau time were found to be the most sensitive indicators of the positive shift (rebound).

Comparative Investigation of Surge Current Capabilities of Si IGBT and SiC MOSFET for Pulsed Power Application

The trend to move toward the solid-state and repetitive pulsed power supply requires the high-voltage, high-current, and high-speed semiconductor devices, which makes an insulated gate bipolar transistor (IGBT) preferred for this application. However, as a bipolar device, the IGBT is limited by the switching speed and switching loss. In this paper, the potential of silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET) for the pulsed power application is investigated. The surge current capabilities of 1.2-kV, 30-A commercial Si IGBT and SiC MOSFET are characterized and compared by the capacitor discharge experiment. In addition, the effects of various circuit parameters, including gate resistance, dc-link voltage, and dc-link capacitance, on the capacitor discharge process are investigated. It is found that the pulse current of SiC MOSFET is around two times of Si IGBT, which achieves good agreement with the datasheet. Using $di/dt$ to represent the discharging speed, the SiC MOSFET is 10 times faster than the Si IGBT. It is because the SiC MOSFET shows a lower ON-resistance in the saturation region resulted from the short-channel effect. This paper confirms the high-speed and high-current advantages of SiC MOSFET in the pulsed power application.

A Sensitive Potentiometric Sensor for Isothermal Amplification-Coupled Detection of Nucleic Acids.

A disposable potentiometric sensor was newly developed for the amplification-coupled detection of nucleic acids. The hydrogen-ion is generally released during isothermal amplification of nucleic acids. The surface potential on the oxide-functionalized electrode of the extended gate was directly measured using full electrical circuits with the commercial metal-oxide semiconductor field-effect transistors (MOSFETs) and ring oscillator components, which resulted in cost-effective, portable and scalable real-time nucleic acid analysis. The current-starved ring oscillator changes surface potential to its frequency depending on the square of the variation in pH with a high signal-to-noise ratio during isothermal amplification. The device achieves a conversion rate of 20.5 kHz/mV and a detection resolution of 200 µV for the surface potential. It is demonstrated that the sensor successfully monitors in real-time isothermal amplification of the extracted nucleic acids from Salmonella pathogenic bacteria. The in situ variations in the frequency of the pH-sensitive sensor were compared with the results of both a conventional optical device and pH-meter during isothermal amplification.

Co-60 gamma irradiation effects on electrical characteristics of HfO2 MOSFETs and specification of basic radiation- induced degradation mechanism

We have studied the effects of Co-60 gamma irradiation on electrical characteristics of metal oxide semiconductor field effect transistors (MOSFETs) with radio-frequency-sputtered Hafnium Oxide (HfO2) gate dielectric, and possible interaction mechanisms between irradiation and HfO2/Si gate stack. The electrical response of the HfO2 devices has been compared with those of experimental and commercial MOSFETs with conventional Silicon Dioxide (SiO2) dielectrics of the similar thickness. We have observed only small threshold voltage shifts during irradiation of the HfO2 MOSFETs; the SiO2 MOSFETs exhibit more than 10 times larger shifts. We have found interesting radiation-induced charge trapping mechanisms by analysis of X-ray photoelectron spectroscopy (XPS) measurements of HfO2/Si gate dielectric stack. The XPS analyses before and after different irradiation doses indicate that both the passivation and charge trapping occurs under radiation exposure. The passivation of dangling bonds significantly decreases the sensitivity of the HfO2 MOSFETs to irradiation. The small threshold shift is predominantly due to the breaking oxygen bonds, especially in HfOx and SiOx core levels. The obtained results demonstrate that the HfO2 based devices are almost insensitive to the irradiation compared to the conventional SiO2 gate and passivation effects significantly decrease radiation sensitivity of HfO2- based device.

TH‐C‐M100E‐10: A Correction Method for the MOSFET Energy Dependence Response to Therapeutic Proton Beams

The energy‐dependence response of the metal oxide semiconductor field‐effect transistor (MOSFET) dosimeter has been investigated with regard to therapeutic proton beams. The MOSFET configurations used include the commercial standard MOSFET (TN‐502RD), the microMOSFET (TN‐502RDM) dosimeters, and a prototype MOSFET with no encapsulation. Proton beams of non‐modulated pristine and modulated Spread‐Out Bragg Peak (SOBP) of 5 cm and 10 cm widths were used with beam ranges of 8.9cm, 15.9cm and 25.9cm in water. Each MOSFET dosimeter was calibrated at the center of the modulated 10 cm SOBP proton beam with conditions of 1 cGy per MU. The MOSFET energy‐dependence response was quantitatively evaluated by the ratio of measured doses between the MOSFET and an ionization chamber in a same condition. The three dosimeters showed a similar response for the pristine proton beams at various beam ranges. This indicates that the variation in dosimeter response is dominated by the change of the linear energy transfer (LET) for the used proton beam and not by the MOSFET encapsulation thickness. The observed MOSFET trends for various pristine proton beams have been modeled by an analytical function , where Rres is the residue range (distance to the distal 90% level dose), and A, B, C are constants. A similar modeling has been performed for modulated SOBP proton beams at different widths and for various beam ranges. The k (Rres) function has been used as a correction factor for patient dose measured by MOSFETs for corresponding residue ranges; this resulted in dose measurements with an uncertainty of less than 3.0% for various proton beams.

Measurement of ionizing radiation using carbon nanotube field effect transistor

Single-walled carbon nanotubes (SWNTs) are a new class of highly promising nanomaterials for future nano-electronics. Here, we present an initial investigation of the feasibility of using SWNT field effect transistors (SWNT-FETs) formed on silicon-oxide substrates and suspended FETs for radiation dosimetry applications. Electrical measurements and atomic force microscopy (AFM) revealed the intactness of SWNT-FET devices after exposure to over 1 Gy of 6 MV therapeutic x-rays. The sensitivity of SWNT-FET devices to x-ray irradiation is elucidated by real-time dose monitoring experiments and accumulated dose reading based on threshold voltage shift. SWNT-FET devices exhibit sensitivities to x-rays that are at least comparable to or orders of magnitude higher than commercial MOSFET (metal-oxide semiconductor field effect transistor) dosimeters and could find applications as miniature dosimeters for microbeam profiling and implantation.

Investigation of the use of MOSFET for clinical IMRT dosimetric verification

(Received 22 October 2001; accepted for publication 26 March 2002; published 22 May 2002) With advanced conformal radiotherapy using intensity modulated beams, it is important to have radiation dose verification measurements prior to treatment. Metal oxide semiconductor field effect transistors (MOSFET) have the advantage of a faster and simpler reading procedure compared to thermoluminescent dosimeters (TLD), and with the commercial MOSFET system, multiple detectors can be used simultaneously. In addition, the small size of the detector could be advantageous, especially for point dose measurements in small homogeneous dose regions. To evaluate the feasibility of MOSFET for routine IMRT dosimetry, a comprehensive set of experiments has been conducted, to investigate the stability, linearity, energy, and angular dependence. For a period of two weeks, under a standard measurement setup, the measured dose standard deviation using the MOSFETs was +/- 0.015 Gy with the mean dose being 1.00 Gy. For a measured dose range of 0.3 Gy to 4.2 Gy, the MOSFETs present a linear response, with a linearity coefficient of 0.998. Under a 10 x 10 cm2 square field, the dose variations measured by the MOSFETs for every 10 degrees from 0 to 180 degrees is +/- 2.5%. The percent depth dose (PDD) measurements were used to verify the energy dependence. The measured PDD using the MOSFETs from 0.5 cm to 34 cm depth agreed to within +/- 3% when compared to that of the ionization chamber. For IMRT dose verification, two special phantoms were designed. One is a solid water slab with 81 possible MOSFET placement holes, and another is a cylindrical phantom with 48 placement holes. For each IMRT phantom verification, an ionization chamber and 3 to 5 MOSFETs were used to measure multiple point doses at different locations. Preliminary results show that the agreement between dose measured by MOSFET and that calculated by Corvus is within 5% error, while the agreement between ionization chamber measurement and the calculation is within 3% error. In conclusion, MOSFET detectors are suitable for routine IMRT dose verification.