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Author: Rahul Radhakrishnan
Publisher:
ISBN:
Category : Diodes, Switching
Languages : en
Pages : 111
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Book Description
Efficiency of power management circuits depends significantly on their constituent switches and rectifiers. The demands of technology are increasingly running up against the intrinsic properties of Si based power devices. 4H-Silicon Carbide (SiC) has superior properties that make it attractive for high power applications. SiC rectifiers are already a competitive choice and SiC switches have also been commercialized recently. Junction Barrier Schottky (JBS) diodes, which combine the advantages of PN and Schottky, have higher Figure of Merit (FOM) as rectifiers. Among switches, a robust and mature process has been developed for Silicon Carbide Vertical Junction Field Effect Transistors (VJFETs), which currently gives it the highest unipolar FOM. Switches are frequently combined with anti-parallel diodes in power circuits. This thesis describes the development of a SiC-based monolithically integrated power switch and diode. Monolithic integration increases reliability and efficiency, and reduces cost. Because of their superior properties and similarities in fabrication, we chose the SiC VJFET and JBS diode as the switch and rectifier. Detailed design, fabrication and characterization of the integrated switch to block above 800 V and conduct current beyond 100 A/cm2 is explained. In this process, the first physics-based 2-D compact model is developed for reverse leakage in a JBS diode as a function of design parameters. Since the gate-channel junctions of SiC VJFETs cannot be assumed to be abrupt, an existing analytical model for Si VJFETs is extended to account for graded gate-channel junctions. Using these analytical models, design rules are developed for the VJFET and JBS diode. Finite element simulations are used to find the best anode layout of the JBS diode and optimize electric field termination in the integrated device to ensure their capability to operate at high voltage. Finally, a spin-on glass based process is developed for filling the gate trenches of the VJFET to improve long-term robustness in extreme environments. The integrated power switch developed in this thesis points to the attractions of monolithic integration in SiC power circuits. Analytical compact design equations derived here will facilitate faster and easier design of switches and rectifiers for desired circuit operation.
Author: Rahul Radhakrishnan
Publisher:
ISBN:
Category : Diodes, Switching
Languages : en
Pages : 111
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Book Description
Efficiency of power management circuits depends significantly on their constituent switches and rectifiers. The demands of technology are increasingly running up against the intrinsic properties of Si based power devices. 4H-Silicon Carbide (SiC) has superior properties that make it attractive for high power applications. SiC rectifiers are already a competitive choice and SiC switches have also been commercialized recently. Junction Barrier Schottky (JBS) diodes, which combine the advantages of PN and Schottky, have higher Figure of Merit (FOM) as rectifiers. Among switches, a robust and mature process has been developed for Silicon Carbide Vertical Junction Field Effect Transistors (VJFETs), which currently gives it the highest unipolar FOM. Switches are frequently combined with anti-parallel diodes in power circuits. This thesis describes the development of a SiC-based monolithically integrated power switch and diode. Monolithic integration increases reliability and efficiency, and reduces cost. Because of their superior properties and similarities in fabrication, we chose the SiC VJFET and JBS diode as the switch and rectifier. Detailed design, fabrication and characterization of the integrated switch to block above 800 V and conduct current beyond 100 A/cm2 is explained. In this process, the first physics-based 2-D compact model is developed for reverse leakage in a JBS diode as a function of design parameters. Since the gate-channel junctions of SiC VJFETs cannot be assumed to be abrupt, an existing analytical model for Si VJFETs is extended to account for graded gate-channel junctions. Using these analytical models, design rules are developed for the VJFET and JBS diode. Finite element simulations are used to find the best anode layout of the JBS diode and optimize electric field termination in the integrated device to ensure their capability to operate at high voltage. Finally, a spin-on glass based process is developed for filling the gate trenches of the VJFET to improve long-term robustness in extreme environments. The integrated power switch developed in this thesis points to the attractions of monolithic integration in SiC power circuits. Analytical compact design equations derived here will facilitate faster and easier design of switches and rectifiers for desired circuit operation.
Author: Yongxi Zhang
Publisher:
ISBN:
Category : Integrated circuits
Languages : en
Pages : 140
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Book Description
4H-Silicon Carbide (4H-SiC) is a promising semiconductor for the next generation of high power, high frequency, and high temperature applications. Significant progresses have been made on SiC technologies since 1990's. Superior device performance demonstrated by SiC discrete power devices is leading to the commercialization of SiC diodes and transistors targeting mid and high power level applications. As compared to the vertical power devices, the lateral device technology promises to fulfill the monolithic integration of both power devices and control circuits. SiC power integrated circuits (PICs) share similar advantages as Si PICs while providing a much higher power handling capability at higher frequency. In addition, SiC power junction field transistor (JFET) is promising for high temperature, reliable operation without suffering from the reliability problems faced by metal-oxide-semiconductor junction field transistors (MOSFETs) and bipolar junction transistors (BJTs). Therefore, the lateral JFET technology is investigated under this research. This thesis describes design, fabrication, characterization, and further optimization and analysis of a novel vertical channel lateral JFET (VC-LJFET) technology in 4H-SiC and the demonstration of the world's first SiC power Integrated circuit. A double reduced surface electric field (RESURF) structure is applied to achieve higher voltage and lower on-resistance for the power lateral JFET (LJFET). A 4-stage buffer circuit based on the resistive-load n-type JFET inverter is designed and integrated with the power LJFET to form a monolithic power integrated circuit. Important fabrication procedures are presented. The fabricated power LJFET demonstrates a blocking voltage of 1028 V and a specific on-resistance of 9.1 m[ohm]; cm2, resulting in a record-high VBR2/RON, SP figure-of-merit (FOM) of 116 MW/cm2 for lateral power devices. The optimized RESURF structure demonstrates blocking capability of 120 V/[micro]m in 4H-SiC. The temperature dependences of important device parameters, such as threshold voltage, transconductance, and electron mobility, are also discussed. Based on the technology, the integration of a high performance lateral power JFET with buffer circuits has been demonstrated for the first time. The SiC LJFET power IC chips demonstrate a record high power level at frequencies up to a few MHz. An on-chip temperature sensing diode is implemented to monitor the chip junction temperature. The rise time and fall time around 20 ns for the SiC power LJFET are observed and remains unchanged even at a junction temperature as high as 250 oC when driven by a Si MOS gate driver. The demonstration of SiC power integration technology points to the robust integrated power electronics applications in the harsh environment and boosts the power level of single-chip power electronic system from 100 W to 1000 W.
Author: Ming Su
Publisher:
ISBN:
Category : Power electronics
Languages : en
Pages : 142
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Silicon carbide (SiC) is a wide-bandgap semiconductor that has drawn significant research interest for the next-generation power electronics due to its superior electrical properties. Excellent device performance has been repeatedly demonstrated by SiC vertical power devices. However, for lateral power devices that offer the unique advantage of possible monolithic integration of a power electronics system-on-chip, the progress has been limited. This dissertation describes the 4H-SiC vertical-channel lateral JFET (VC-LJFET) technology that provides a suitable solution for power integration applications. Power devices based on this structure have a trenched-and-implanted vertical channel and a carefully designed lateral drift region, enabling normally-off operation with a high-voltage blocking capability. Low-voltage (LV) versions of VC-LJFET feature nearly identical device structures with a reduced drift length, and can be readily fabricated on the same wafer with the power devices. Essential components for a power integrated circuit, such as gate drive buffers, can be thus implemented monolithically on the VC-LJFET technology platform. This dissertation research starts with the process improvement investigation for the TI-JFET structure. Particularly, a novel ohmic contact scheme is developed using Ni to replace the troubling process in TI-VJFETs. The entire process flow of VC-LJFET is then designed and demonstrated in experiments, leading to the world's first demonstration of a normally-off lateral power JFET in SiC. As of today, power JFETs fabricated in this technology are still representing the best-performing lateral power transistors in SiC and silicon. Based on the VC-LJFET structure, low-voltage circuits critical to the power integration applications are investigated. Gate drive buffer provides the interface between low-voltage control circuits and the power device, and is recognized as a key component for an integrated power electronics system. A thorough design, modeling and optimization work on the LJFET-based gate drive circuits is described. These buffer drivers using resistor or transistor loads will enable high-frequency switching of the power LJFETs at megahertz levels. The results achieved in this research strongly suggest the feasibility of SiC power integration technologies in general, as well as the suitability of the SiC VC-LJFET platform for such applications in particular.
Author: Luo, Xixi
Publisher:
ISBN:
Category :
Languages : en
Pages : 116
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A novel design of mesa-etch termination and Superjunction JBS diode structure has been proposed and optimized. The new mesa-etch termination can achieve over 90% of ideal maximal breakdown voltage within a wide sidewall implant dose window (~9e16 cm−3). Besides the high tolerance on implant dose, the proposed design also exhibits high tolerance on the etch sidewall angle: minimal maximum breakdown voltage was observed with etch sidewall angle variations. The Superjunction JBS diode can obtain both 96.4% maximum super junction breakdown voltage and 76.6% JBS Schottky surface electric field reduction. The super junction maximal breakdown voltage is 1.5 times large as the conventional Schottky diode breakdown voltage and the leakage current is logarithmically related to the surface electric field. The superior breakdown voltage represents a large improvement on the power rectifier performance. Based on these structure improvements, vertical 4H-SiC Schottky Diodes have been fabricated and tested. Vertical 4H-SiC Schottky Diode without any edge termination has a breakdown voltage as large as 692 V and exhibits an on-state specific resistance as small as 7.9 mΩ*cm2. Such breakdown voltage is much higher than simulation results. In the meantime, on-state resistance is also much larger than the simulation results. The mechanism for these improved power rectifier performances will be furthered investigated in future studies
Author: Dominique Johanne Morrison
Publisher:
ISBN:
Category :
Languages : en
Pages : 171
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Author: Ryan C. Edwards
Publisher:
ISBN:
Category : Diodes, Schottky-barrier
Languages : en
Pages : 124
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Author: Krishna Chaitanya Kundeti
Publisher:
ISBN:
Category : Diodes, Schottky-barrier
Languages : en
Pages : 142
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Titanium (Ti) is a popular metal contact used in fabricating Schottky barrier diodes on silicon carbide (SiC) semiconductor. In this research, Ti/4H-SiC Schottky barrier diodes have been fabricated to investigate the effect of deposition temperature and annealing on the electrical characteristics of the fabricated devices. The parameters such as barrier height, ideality factor and on-resistance were determined from the current-voltage (I-V) and the capacitance-voltage (C-V) measurements at room temperature. The temperature-dependent electrical characteristics are realized by performing current-voltage-temperature (I-V-T) measurements. Furthermore, the material characterizations were performed using Auger Electron Spectroscopy (AES) and x-ray diffraction (XRD) measurements. Thin films of Titanium (Ti) as Schottky contacts were deposited on n-type 4H-SiC substrate by magnetron sputtering at different temperatures form room temperature ~25 °C to 900 °C. In addition, thermal processing was performed by annealing at 500 °C in vacuum and argon environment up to 60 hours and characterized using I-V, C-V, and I-V-T measurements accordingly. The diodes with Ti deposited at 200 °C yield better devices with an average ideality factor of 1.04 and Schottky barrier height of 1.13 eV. The electrical properties shows that the deposition of Schottky contact should be at least below 700 °C and the Schottky contact should be annealed at 500 °C for 12-36 hours in order to obtain acceptable quality of Schottky diode. We believe that these variations in the electrical properties are due to the change in the quality of interfacial layer. The variations in physical/compositional properties of Ti/SiC interface has been investigated using Auger electron spectroscopy and x-ray diffraction, which reveled mainly two kinds of phases: Ti5Si3 and Ti3SiC2 formed at the interfacial layer.
Author: Eskinder Hailu
Publisher:
ISBN:
Category :
Languages : en
Pages : 482
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Author:
Publisher:
ISBN:
Category : Chemistry
Languages : en
Pages : 2692
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Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 920
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