The Optimization Of 100V Shielded Gate Trench Power MOSFET With High Avalanche Ruggedness And Low On-resistance

Compared with the traditional power MOSFET,SGT-MOSFET has lower energy consumption,so SGT-MOSFET is widely used in the field of new energy electric vehicles.At present,compared with similar products made by foreign manufacturers,domestic SGT-MOSFET has the problems of large on-resistance and low avalanche ruggedness,therefore,reducing the on-resistance and increasing the avalanche ruggedness are essential to enhance the competitiveness of domestic SGT-MOSFET.In this thesis,the structure and layout of the device are optimized based on the failure analysis of the SGT-MOSFET in unclamped inductive switching process.First of all,this thesis has carried on a large number of EAS tests to the existing SGT-MOSFET samples and has found the two reasons that lead to the EAS failure of SGT-MOSFET combined with the computer simulation.The first point is that the avalanche ruggedness is closely related to the negative resistance characteristic at breakdown and the higher the snapback current,the greater the avalanche ruggedness of the device.The second point is the phenomenon of current concentration in the EAS process.In three cases,the current is concentrated,the first is that the current in the EAS is centered at the terminal because the breakdown voltage of the terminal is lower than the cell,the second is because the parasitic gate resistance causes the switching speed of the gate in the device to be different,and the higher the parasitic gate resistance is,the slower the device turns off,so the current will be concentrated at the point where the turn off speed is slow,the third is the parasitic shielded gate resistor,which causes the breakdown voltage to be nonuniform during the EAS process,so that the current is concentrated at the point where the breakdown voltage is small.Then,based on the relation between snapback current and avalanche ruggedness,a double epitaxy structure with high avalanche reguddness and low on-resistance is adopted.In order to improve the terminal breakdown voltage,a terminal structure with wider terminal trenchs is adopted.In order to reduce the parasitic gate resistance,a tie structure is added to the layout.In order to eliminate the parasitic shielded gate resistance,a direct contact structure between source metal and shielded gate in active region is adopted.The results of the test show that the avalanche reguddness of SGT-MOSFET designed in this thesis rises by 114%compared with the original device under the condition that the inductance is 0.5mH,and the on-resistance is decreased by 9.4%,which meets the application requirements of new energy electric vehicles.