| Superjunction MOSFET(SJ-MOS) has gradually replaced the traditional VDMOS in many fields due to its low conduction loss,but its further application in the radiation environment such as aerospace will be limited by single event effect(SEE).Based on the lack of research on SEE and reinforcement of SJ-MOS at home and abroad,the SEE of the cell and termination of SJ-MOS are simulated and theoretically analysed in this thesis,and then the corresponding anti-radiation improvement measures are put forward.The main research work of this article is as follows:Based on the basic theories of SJ-MOS and radiation effects,the structures of cell and termination are respectively designed.Moreover,their single event effects are simulated and analyzed in depth,including the SEB effect and SEGR effect of the cell and SEB effect of the termination.Specifically,the physical mechanisms,radiation conditions(incident position and depth) and bias conditions of SEB effect or SEGR effect are analyzed and discussed.The simulation and analysis results of the cell show that the mechanism of SEB failure is concerned with the conduction and current amplification of parasitic BJT,and the mechanism of SEGR failure is related to the sharply increase of electric field on the lower surface of gate oxide caused by the accumulation of radiation-induced holes.SEB failure is more likely to occur when the high-energy particle penetrate from left and right sides of JFET region,and SEGR failure is more likely to occur when the particle penetrate from the center of JFET region,and the probability of these two failures increases with the increase of the incident depth or drain bias.It's found that the cell can be hardened against SEB by restraining the turning on of parasitic BJT and reducing its current gain,and hardened against SEGR by optimizing the gate dielectric layer and controlling the concentration of holes beneath gate oxide.In this thesis,some reinforcement measures,such as thick oxygen over JFET region,deep-P~+ structure,P-bury layer,N-buffer layer,doping reduction of N~+-source,hole-bypass structure and non-uniform doping of P/N column are provided and verified.The simulation and analysis results of the termination show that the SEB failure is due to the concentration of curren at the edge of the contact above the equipotential ring caused by the radiation-induced holes,which results in a local hot spot and burnout.The SEB failure is more likely to occur when an energetic particle passing through the region near the equipotential ring,and the possibility of SEB failure will increase with the increase of injection depth and drain-source voltage.The radiation hardening of termination can be achieved by controlling the density of holes flowing through the contact of equipotential ring.Then three improvement measure:ballast resistance,N-buffer layer and P-bury layer,are provided and verified by simulation respectively.The failure mechanisms of SEE of SJ-MOS and its influencing factors are analyzed in depth and the corresponding radiation hardening scheme is provided in this article,which is of great significance for the design and improvement of radiation-resistant SJ-MOS. |
