The Study Of Novel Trench SOI—LDMOS With High Breakdownvoltage

With the change of time,high-voltage power integrated circuits have been developed rapidly and more widely used.LDMOS(Lateral Double-diffused MOS,LDMOS),as one of the key devices in power integrated circuits,could play a more important role in the field of semiconductor devices because of its high input impedance,high conversion rate and easy integration.On-resistance and breakdown voltage are two key parameters for LDMOS to measure device performance.However,the reduction of on-resistance is often at the expense of breakdown high-voltage performance.In order to weigh the relationship between the two factors and improve device performance,two new trench LDMOS structures are proposed in this dissertation.The first proposed device is a SOI LDMOS with trapezoidal trench and vertical field plate(TT FP SOI LDMOS).Trapezoidal trench and vertical field plate can modulate the electric field in the drift region,and improve the breakdown high-voltage performance of the device.Trapezoidal trench results in decreasing the length of the drift region,which can shorten the current path and thus reduce the on-resistance of the device.Compared with the conventional trench SOI LDMOS and rapezoidal trench SOI LDMOS,the breakdown voltage can reach 622.6V,for TT FP SOI LDMOS,and the on-resistance is reduced by 93.95% and 66.48%.As result,it achieves a high quality factor(figure-of-merit,FOM)of 9.74 MW/ which breaks the silicon limit.The second proposed device is a trench SOI LDMOS structure with P/N pillars(P/N Trench SOI LDMOS).The characteristic of this structure is the introduction of rectangle P-type pillar,L-shaped P-type pillar and reverse L-shaped N-pillar.These three pillars can optimize the electric field by charge compensation.Additional electric field peaks occur in the device body,which makes the electric field distribution uniform,and improves the breakdown performance of the device.The highly doped reverse L-shaped N-type pillar increases the average doping concentration of the drift region and thus reduce the on-resistance of the device.In addition,the electric field at the interface between the L-shaped P-type pillar and the reverse L-shaped N-type pillar produces obvious humps,which optimizes the electric field distribution.Compared with the conventional trench SOI LDMOS of the same device size,the breakdown voltage is enhanced by 155V(606V),for P/N Trench SOI LDMOS,while the on-resistance is reduced by 64%.