Device Key Technology And Device Research Of High Current SiC MOSFET

Silicon carbide?SiC?has been recognized as a promising materials for the high power and high temperature switching devices such as metal-oxide-semiconductor field-effect transistors?MOSFETs?,attributed to its suitable properties.A few domestic groups have reported their results on SiC MOSFETs,however,the forward current characteristic of their results still needs to be optimized.In this thesis,structure simulation and fabrication process have been explored to enhance the forward current characteristic based on the domestic experiment conditions.In this work,SiC MOSFETs cell and terminal structure were simulated by numerical simulation software Silvaco.Cell parameters were elaborately choosen to obtain favourable forward current characteristic and breakdown voltage.To meet the needs of our novel self-aligned proecess terminal structure was redesigned,the improved terminal structure can maintain acceptable breakdown voltage even at higher ion implantation dose.Moreover,several process experiments that can contribute to current enhancement have been conducted.To fabricate short channel SiC MOSFETs self-aligned proecess has been designed.Then,SiC ohmic contact process was developed to decrease contact resistance.Furthermore,a novel SiC oxidation method has been explored to optimize the poor SiC/SiO₂ interface quality.At last,an ESD structure was simulated and tested to ameliorate gate oxide robustness.The high current 1200 V SiC MOSFETs were fabricated in two different methods based on the experimental results mentioned above.The the output current of the devices manufactured in non-self-aligned process is 26A@VGS=20V,VDS=5V.When it comes to the self-aligned proecess devices,the output current is 34A@VGS=20V,VDS=5V.But for part of the self-aligned devices the threshold voltage is abnormal.A comprehensive simulation was applied to analyze the abnormal transfer characteristics.High near interface density and relatively short channel length will contribute to this phenomenon.The channel carrier mobility was extracted from the lateral MOSFETs fabricated simultaneously.Reliable value of the channel carrier mobility was 20 cm2/V·s.In this thesis,the structure design and key process technology has been successfully researched based on domestic SiC experiment condition.These results were used to fabricate 1200V/30 A SiC MOSFETs.This work provides a reference for domestic high current 1200 V 4H-SiC MOSFETs development.