Analytical Model And Characteristics Of VDMOS Device

VDMOS(Vertical Double-diffused MOSFET)is a widely used semiconductor device at present,and has always been aimed at optimizing the trade-off relationship between breakdown voltage(BV)and on-resistance(Ron,sp).Now,the research on VDMOS mainly focuses on finding a new pres sure-resistant layer structure,but there is no effective means for the model research of the device.In this paper,a two-dimensional potential model of High-K(HK)VDMOS with interface charge is established by means of equivalent superposition transformation.The variation mechanism of device performance with structural parameters is studied.And on this basis,an improved high-k structure is proposed,which further optimizes the trade-off relationship between BV and Ron,sp.Firstly,this paper studies the working principle of conventional super junction structure and HK structure,and analyzes the electric field distribution and pressure resistance mechanism of two kinds of withstand voltage structures.Then,according to the principle of total charge conservation and conservation of electric flux,the structure of HK VDMOS device is equivalent to the superposition of SJ structure and p-i-n structure.The effect of interface trap charge(Qit)is studied separately.Based on the two-dimensional Poisson equation,the potential and electric field models of the device are established,and the approximate model of the optimal BV and Ron,sp is obtained.The simulation results of MEDICI show that the model is almost identical to the simulation results.Finally,combined with the basic working principle of SJ structure and HK structure,an improved HK VDMOS device(HKP-VDMOS)with p-doped region is proposed.In HKP-VDMOS devices,the breakdown voltage is increased by introducing a peak electric field in the body.In addition,the p-type region can assist in the depletion of the drift region,thus achieving a reduction in specific on-resistance.Based on the Poisson equation,the two-dimensional potential analysis model of HKP-VDMOS device is established,and the approximate model of the optimal BV and Ron,sp is obtained.The analytical model and the simulation results are in good agreement,with errors within 5%.Compared to the conventional HK VDMOS device,the improved device has a specific on-resistance Ron,sp that is reduced by 16.7%at the same breakdown voltage BV.