Breakdown Theory of SOI Lateral Super Junction Devices
|School||Nanjing University of Posts and Telecommunications|
|Course||Circuits and Systems|
|Keywords||SOI Super Junction (SJ) Model Surface Potential Surface electric field Breakdown Voltage 3D RESURF On-state Resistance|
The conflicting between on-resistance and breakdown voltage is one of the core problem in power semiconductor devices. Super Junction (SJ) technology has a wide of application prospect in the traditional power IC due to the break of the limit relationship of on-resistance and breakdown voltage. The standing-voltage mechanism of SJ devices is completely different from conventional power devices, thus it is great significant to investigate. To this day, however, the standing-voltage mechanism of the lateral SJ devices is studied less than the vertical SJ devices. Therefore, in this paper, we develop the 3D analytical models for the six common SOI lateral SJ devices (charge balance, doping concentration unbalance, width unbalance, completely unbalance, linearly doping concentration and linearly pillar width) by solving three-dimensional Poisson equation, respectively. All these provide the theoretical guidance for the design and optimization of SOI lateral SJ power devices. The thesis includs:1) Analytical models of surface potential and electric field distributions of SOI lateral SJ power devices. Firstly, we solve the three dimensional Poisson equation in the fully-depleted/partial-depleted drift regions The 3D analytical models of the surface potential and the surface electric fields distributions are developed for the different SOI lateral SJ devices. Then, 3D numerical simulation tool DAVINCI is used to simulate the surface potential and electric fields distributions for different devices. The results are compared to the analytical models. The availability are verified by the accordance between them.2) Impact of device parameters on the surface potential and surface electric fields distributions. Based on the models above and the 3D numerical simulation tool DAVINCI, the surface potential and electric fields distributions are analyzed and the physical insight are explored when the device parameters vary. These device parameters include the doping concentration, width, length and height of the p-pillar and n-pillar, as well as the buried oxide thickness. These contribute a theoretical basis for the design and performance optimization of SOI lateral SJ devices.3) Breakdown voltage modes of SOI lateral SJ power devices. Based on the models of surface potential and electric fields distributions above, we propose the analytical breakdown models of SOI lateral SJ devices. The expressions of lateral and vertical breakdown voltages are derived. The 3D RESURF criterions are carried out for different SJ devices.The optimization and design of the conventional SOI N-LDMOS, SOI SJ-LDMOS with unbalance doping concentration, and SOI SJ-LDMOS with linearly pillar width are preformed based on the proposed criterions, respectively. Finally, the 3D numerical simulation tool DAVINCI is used to verify the availability of the design.