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Design and fabrication of 4H silicon carbide MOSFETS
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Text
TitleInfo
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Title
Design and fabrication of 4H silicon carbide MOSFETS
Identifier
ETD_1356
Identifier
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http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.000051080
Language
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eng
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theses
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Topic
Electrical and Computer Engineering
Subject
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(authority = ETD-LCSH)
Topic
Metal oxide semiconductor field-effect transistors--Design and construction
Abstract
The 4H-SiC power MOSFET is an excellent candidate for power applications. Major technical difficulties in the development of 4H-SiC power MOSFET have been low MOS channel mobility and gate oxide reliability. In this dissertation, a novel 4H-SiC power MOSFET structure has been presented with the aim of solving these problems.
The research started from the study and improvement of the channel mobility of lateral trench-gate MOSFET that features an accumulation channel for high channel mobility. The design, fabrication and characterization of lateral trench-gate MOSFET are presented. The fabricated lateral trench-gate MOSFET with an accumulation channel of 0.15μm exhibited a high peak channel mobility of 95 cm2/Vs at room temperature and 255 cm2/Vs at 200oC with stable normally-off operation.
Based on the successful demonstration of high channel mobility, a vertical trench-gate power MOSFET structure has been designed and developed. This structure also features an epitaxial N-type accumulation channel to take advantage of high channel mobility. Moreover, this structure introduces a submicron N-type vertical channel by counter-doping the P base region via a low-dose nitrogen ion implantation. The implanted vertical channel provides effective shielding for gate oxide from high electric field.
A process using the oxidation of polysilicon was developed to achieve self-alignment between the submicron vertical channel and the gate trench. A "sandwich" process, including nitric oxide growth, dry oxygen growth and nitric oxide annealing, was incorporated to grow high-quality gate oxide.
The fabricated single-gate vertical MOSFET can block up to 890 V at zero gate bias. The device exhibited a low specific on-resistance of 9.3 mΩcm2 at VGS=70 V, resulting in an improved FOM ( ) of 85 MW/cm2. A large-area MOSFET with an active area of 4.26x10-2 cm2 can block up to 810V with a low leakage current of 21μA and conducted a high on-current of 1 A at VDS=3 V and VGS=50 V. The fabricated devices all exhibited the stable normally-off operation with threshold voltages of 5~6 V. Their subthreshold characteristics with high on/off ratios of 3~5 indicates that the MOSFETs are capable of operating stably as switching devices.
The research started from the study and improvement of the channel mobility of lateral trench-gate MOSFET that features an accumulation channel for high channel mobility. The design, fabrication and characterization of lateral trench-gate MOSFET are presented. The fabricated lateral trench-gate MOSFET with an accumulation channel of 0.15μm exhibited a high peak channel mobility of 95 cm2/Vs at room temperature and 255 cm2/Vs at 200oC with stable normally-off operation.
Based on the successful demonstration of high channel mobility, a vertical trench-gate power MOSFET structure has been designed and developed. This structure also features an epitaxial N-type accumulation channel to take advantage of high channel mobility. Moreover, this structure introduces a submicron N-type vertical channel by counter-doping the P base region via a low-dose nitrogen ion implantation. The implanted vertical channel provides effective shielding for gate oxide from high electric field.
A process using the oxidation of polysilicon was developed to achieve self-alignment between the submicron vertical channel and the gate trench. A "sandwich" process, including nitric oxide growth, dry oxygen growth and nitric oxide annealing, was incorporated to grow high-quality gate oxide.
The fabricated single-gate vertical MOSFET can block up to 890 V at zero gate bias. The device exhibited a low specific on-resistance of 9.3 mΩcm2 at VGS=70 V, resulting in an improved FOM ( ) of 85 MW/cm2. A large-area MOSFET with an active area of 4.26x10-2 cm2 can block up to 810V with a low leakage current of 21μA and conducted a high on-current of 1 A at VDS=3 V and VGS=50 V. The fabricated devices all exhibited the stable normally-off operation with threshold voltages of 5~6 V. Their subthreshold characteristics with high on/off ratios of 3~5 indicates that the MOSFETs are capable of operating stably as switching devices.
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electronic resource
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viii, 158 p. : ill.
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Note
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Ph.D.
Note
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Includes bibliographical references (p. 151-156)
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by Jian Wu
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Wu
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Jian
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Jian Wu
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Zhao
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Jian
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Jian H Zhao
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Sheng
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Kuang
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Kuang Sheng
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Jiang
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Wei
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Wei Jiang
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Weiner
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Maurice
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Maurice Weiner
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Rutgers University
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Graduate School - New Brunswick
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2009
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2009-01
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xx
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NjNbRU
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Rutgers University Electronic Theses and Dissertations
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Graduate School - New Brunswick Electronic Theses and Dissertations
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rucore19991600001
Identifier
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doi:10.7282/T3154H8F
Genre
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ETD doctoral
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The author owns the copyright to this work.
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Copyright protected
Availability
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Open
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Non-exclusive ETD license
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Author Agreement License
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I hereby grant to the Rutgers University Libraries and to my school the non-exclusive right to archive, reproduce and distribute my thesis or dissertation, in whole or in part, and/or my abstract, in whole or in part, in and from an electronic format, subject to the release date subsequently stipulated in this submittal form and approved by my school. I represent and stipulate that the thesis or dissertation and its abstract are my original work, that they do not infringe or violate any rights of others, and that I make these grants as the sole owner of the rights to my thesis or dissertation and its abstract. I represent that I have obtained written permissions, when necessary, from the owner(s) of each third party copyrighted matter to be included in my thesis or dissertation and will supply copies of such upon request by my school. I acknowledge that RU ETD and my school will not distribute my thesis or dissertation or its abstract if, in their reasonable judgment, they believe all such rights have not been secured. I acknowledge that I retain ownership rights to the copyright of my work. I also retain the right to use all or part of this thesis or dissertation in future works, such as articles or books.
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