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The SOI field-effect Hall sensors are characterized by the enhanced functionality, but by low magnetic sensitivity. Therefore, the main task is to increase the magnetic sensitivity of such sensors. The results of the study on magnetically sensitive electric characteristics of SOI FEHS, obtained using the TCAD system, have been presented. The three-dimensional modeling of the device has been carried out. The calculated Hall-gate characteristics of SOI FEHS, confirming the previously proposed physical model of the sensor, in accordance with which under certain conditions of SOI FEHS functioning the area of the increased magnetic sensitivity appears, have been obtained. The influence of the doping concentration in the sensor channel on the magnetic sensitivity has been studied. It has been shown that the magnetic sensitivity of SOI FEHS is 3 times increased at the concentration of 10 cm. The extended dynamic range of the increased magnetic sensitivity area (more than 5 V) permits to increase the area of practical application of the sensor increasing the noise immunity. The obtained SOI FEHS characteristics are in good agreement with the parameters of the experimental device published earlier.
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For multi-factor analysis of instrument characteristics of the field-effect Hall sensor on the SOI structure (SOI FEHS), by means of the TCAD simulation, the calculation of the output and transfer characteristics of SOI FEHS) two-dimensional model has been performed. The two-dimensional distributions of electrons of electric field and the current density in the SOI FEHS channel have been obtained in three typical modes of the sensor operation - full depletion, partial depletion and saturation. The obtained results are in good agreement with the experimental data and confirm the physical model of SOI FEHS, described above, and specific features of the instrument operation in the partial depletion region, when the conductive channel in SOI FEHS body is formed.
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The junctionless MOSFETs have a number of advantages compared to traditional ones in terms of the design simplicity, manufacturing technology and reducing the impact of short-channel effects upon the device characteristics. However, the known experimental nanowire JLT MOSFETs have high threshold currents due to parasitic bipolar transistor appearance in a closed state. A design of the device with a low impurity concentration in the working body and having the strongly doped contacts to the drain-source areas has been proposed. Using the device-technological modeling in the TCAD system, the influence of the contacts relative to the gate electrode on the main parameters of SOI MOS JLT has been studied. With the use of the Sentaurus Structure Editor the structural model of JLT MOSFETs with various thicknesses of a spacer, which determines the distance between the gate electrode and the contact drain-source areas, have been built, and the calculations of the I-V characteristics at a drain voltage of 0.1 V and 1.2 V have been performed. Transient VAC at the drain voltage 0.1 and 1.2 V have been calculated. By the transient characteristic with supply voltage at the drain of 1.2 V the curves of the threshold currents, the saturation currents and current-to-current ratio in the off state versus the size of the drain-source areas have been plotted. As a result of the research a new short-drain effect, dramatically reducing the threshold voltage, has been discovered and explained. This effect becomes apparent under the impact of SCR of the n + n transition between the contact and the drain on the channel region charge, when the distance between the gate electrode and the contact becomes less than 100 nm. While forming planar JLT MOSFETs according to the 90 nm technology it is necessary to create the drain-source regions with the size of 25 nm and to assign the concentration in the n-channel transistor 6 · 10 16 cm and in p-channel one - 5 · 10 16 cm. This will allow reducing the subthreshold currents of the device to 10 Aμm and to obtain a current ratio in the open and closed state 10. The most optimal size of the spacers thickness is from 160 to 340 nm, with which the influence of the contact n n transitions and sequential resistance of the drain-source regions on JLT MOSFET parameters, has been determined.
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The influence of the doping concentration in the active layer and in the bulk substrate on the drain current of the SOI field by the Hall sensor device-technological simulation package Synopsys Sentarius has been studied. At the initial stage the numerical model correction has been performed by comparing the transmission current-voltage characteristics of the calculation and the previously created and experimentally measured sample SOI FEHS. It has been shown that at low concentrations in the active layer the drain current depends on the capacity of the front gate and the doping concentration level of the bulk substrate affects the drain current only when the device is operating in depletion mode.
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The sensitivity and the initial offset of voltage between the collectors of the two-collector lateral bipolar magnetotransistor of npn-type with the base, formed in the well being the third collector (3KBMTBW) at the reduced rate of the surface recombination in the base, have been experimentally investigated. The magnetotransistor switch-on circuit determines the operation mode and the device parameters. It has been shown, that the magnetosensitivity of voltage achieves 11 V/T.
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Previously, during investigation using the apparatus-technological simulation of SOI field-effect Hall sensor in the partial depletion mode an effect of its magnetic sensitivity has been discovered. In the work, in order to experimentally confirm the observed effect, the samples of SOI FEHS have been made and their parameters have been investigated in various modes of their operation. In order to improve the accuracy of measurements in the partial depletion mode the SOI FEHS design with a split drain has been used. The optimum load resistances of the bridge circuit have been determined. The analysis of the investigation of SOI FEHS samples has shown that in the mode of partial depletion, a peak of increased sensitivity has been observed. With the nominal load resistances of 1 MΩ and supply voltage of -9 V, the maximum magnitude of the magnetically induced signal increases by about 3 times in the mode of partial depletion versus full depletion. When recalculating the voltage difference across the load resistances DV to the magnetosensitivity, the magnetic sensitivity in the partial depletion mode can reach the values of 10 V/A·T, which is significantly higher than any known Hall semiconductor elements.
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Studies in the field of creating new structures of Hall sensors with improved characteristics, in particular with increased magnetics sensitivity, are very promising. In this study, we derive an analytical model that explains the features of Hall-gate characteristics and appearance of the area of high magnetics sensitivity of the SOI field-effect Hall sensor. The simulation results in the Synopsys Sentaurus TCAD confirm the analytical model proposed in this work. The proposed physical model explains the features of the Hall-gate characteristics of SOI FEHS in a wide range of gate voltages and allows us to conclude that the SOI FEHS has two working areas of operation and their choice is determined by the specific conditions of the sensor application. It is necessary to select the mode of partially depletion and enhancement to achieve maximum magnetics sensitivity. It is advisable to select a full enhancement mode to provide high noise immunity.
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Junctionless MOSFETs have a number of advantages over the traditional ones in terms of simplicity of design, manufacturing technology and reducing the impact of the short-channel effects on the device characteristics. However, the known experimental nanowire MOSFETs have high subthreshold currents due to the parasitic bipolar transistor appearance in the closed state. A structural model of a planar SOI in accordance with the technology standards of 90 nm and the route of mathematical modeling have been developed. The influence of the impurity concentration in the SOI MOSFET silicon film on the threshold voltage, the saturation currents and subthreshold currents using TCAD environment has been investigated. The investigation results show that if the impurity concentrations in the working body of the device is below 10 cm and there is no interband tunneling effect, and a parasitic bipolar transistor does not arise, the subthreshold currents decrease to 10 A/μm, while maintaining the saturation currents at an acceptable level, which is significantly lower than those of the conventional MOS transistors.
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The simulation of the primary gas flow rate converter of membrane type based on the operation calorimetric principle has been carried out. Several options of the sensor construction have been considered. The results of numerical modeling for different variants of the sensor design in terms of the maximum sensitivity have been analyzed. The results permit to find the optimal for the moment the thermal sensor configuration and location.
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The lateral junctionless MOSFET’s have a number of advantages compared to the conventional devices based on SOI structure. During the process of fabricating SOI structure and further technological operations of fabricating transistors, the change of the silicon film thickness is possible. In the work, using the device-technological modeling in the TCAD system the results of the studies on the influence of the SOI structure silicon film thickness on the main JLT parameters have been presented. It has been shown that to compensate the degradation of the device characteristics while changing the silicon film thickness it is necessary, respectively, to change the impurity concentration in silicon. For this, with the silicon film thicknesses less than 45 nm the level of the silicon film doping by the impurity higher than 10 cm is necessary.
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It has been found that the relative current sensitivity of the current dual-collector lateral bipolar magnetotransistor is determined by the layout of electrodes, the dopant distribution in well (also the base of BMT), the circuit of switching-on with the general potential of the basis and substrate, an operation mode near to saturation, the value of collectors load resistance.
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