Research On Theories And Key Technologies Of Power Schottky Rectifiers

Nowadays, supply of energy is far less than the actual demand. Therefore "renewablesources" and "restructuring" are the two most fundamental solutions. In addition, utilizingpower electronic devices in the production of electricity may help improve system efficiency,reduce energy costs, which are "restructuring" category. And the primary significance of thedevelopment of power electronics is to save energy. Power Schottky diodes are one of themost basic semiconductor devices and the forward voltage drop, breakdown voltage, outputcapacitance etc are a few key performance indicators. To achieve high voltage and low energycosts devices, the studies of power Schottky diodes will be run from two directions: one isthat the use of new theories or new structures improve the contradictory relationship of powerSchottky diodes between conduction losses and switching costs following the mature silicondevice technology; the other is that it takes advantage of wide bandgap semiconductormaterial e.g. silicon carbide (SiC) to improve the performance of power Schottky diode.This thesis reviews the system requirement and latest development of power Schottkydiodes. Besides, emerging wide bandgap semiconductor material such as SiC and theirsuperior properties are also reviewed. The theory and performance of Schottky barrier diode(SBD) and junction barrier Schottky (JBS) rectifier are studied. The goal of Si SBD and4H-SiC JBS devices design is to obtain power Schottky diodes with high performance, lowpower consumption, low cost and high reliability in the field. This paper presents the resultsof a thorough study, made possible by Silvaco TCAD tools, of the impact of dual epitaxiallayers and P-well on power Schottky diodes performance. Dual epitaxial layers are consideredto decrease the specific on-resistance of devices and it is useful to optimize electric fielddistribution of devices by P-well.Firstly, the design of45V and100V Si SBD is using dual epitaxial layers by theoreticalcalculation in order to reduce the static and dynamic losses and the cell size. Then we proposetwo junction termination structures:(1) POP, the P+guard rings are on the P-well and thewidth of P-well is smaller than that of the P+guard rings;(2) PIP, the P+guard rings are in theP-well. This two junction termination structures are applied to the Si SBD to improve theelectric static discharge protection of devices. Secondly, POP-JBS and PIP-JBS rectifiers areproposed:(1) POP-JBS, the P+grids and P+guard rings are on the P-well and the width ofP-well is smaller than that of the P+guard rings;(2) PIP-JBS, the P+grids and P+guard ringsare in the P-well. These two structures improve the breakdown voltage and the electric static discharge protection of4H-SiC JBS rectifiers. The theoretical calculation, optimization andsimulation of POP-JBS and PIP-JBS rectifiers are completed. As a result, the breakdownvoltage of1.9kV was obtained for the POP-JBS rectifier, and that of the PIP-JBS rectifier isabout1.6kV. In addition, the fabrication processes and layouts of POP-SBD, PIP-SBD,POP-JBS and PIP-JBS are proposed. Finally, the summary and analysis of this thesis play arole in the study of power Schottky diodes, and the future of power Schottky diodes isdiscussed.