Characteristics Analysis And Design Of SJ MOSFET

SJ MOSFET is a new development power MOSFET based on the combination of VDMOS and SJ (Super Junction), and called the new milestone of power MOSFET. SJ MOSFET has extensive application foreground and the product is still the undeveloped interiorly now.The structure, principle, characteristics and fabrication process are analyzed systemically in this thesis. Based on the analysis of breakdown mechanism and characteristics of SJ, the characteristics and key processes of SJ MOSFET and Semi-SJ MOSFET are simulated using ISE simulator, and the design methods of key parameters are also given. And an oxide filled extended trench gate SJ MOSFET is presented. The characteristics and key process of the new device structure are analyzed. The main content is as follows:Firstly, the breakdown mechanism and characteristics of Super Junction are studied. The results show that the maximum electric field is at the middle of the lateral pn junction, and transfers from the middle of lateral pn junction to the middle of vertical pn junction with the increase of the concentration of pillar regions. Based on the results, the influence of charge imbalance on breakdown voltage of SJ is also discussed.Secondly, the characteristics of SJ MOSFET and its influencing factors are analyzed. The results show that characteristics of SJ MOSFET are related to the thickness, concentration and width of pillar regions. When charge balance between the n pillar and p pillar regions is satisfied, the breakdown voltage (BV) of SJ MOSFET is only related to thickness of pillar regions and increases with the increase of the thickness. BV begins to decrease abruptly once the pillar concentration is larger than the critical value; the smaller pillar width is helpful to decrease R_on. And two design schemes of the minimum R_on and the lowest cost are presented out and the corresponding extraction methods of key parameters are given.Thirdly, the characteristics of Semi-SJ MOSFET and its influencing factors are analyzed. The results show that increase extent of BV decreases gradually and the influence of BAL on BV and R_on decreases with the increase of ratio of pillar thickness and BAL thickness.Fourthly, an oxide filled extended trench gate SJ MOSFET is presented, and the characteristics are analyzed and compared with conventional trench gate SJ MOSFET. The results show that the blocking, conducting and switching characteristics of this new structure are improved obviously.Fifthly, based on the characteristics design results, the process of p-base, n⁺ source and SJ regions of SJ MOSFET are simulated. And the key fabrication process of the new structure is analyzed, the process condition of the shallow angle implantation forming n pillar region is given.The research results have a reference value for the further study of the new structure of SJ MOSFET and the development of SJ MOSFET device.