Research On Lateral Power MOSFET With Dielectric Deep Trench

Lateral power MOSFETs occupies an important position in the field of power integrated circuits because of their advantages such as fast switching speed and easy integration.There is an important trade-off relationship in power devices,that is,the trade-off relationship between specific on-resistance and breakdown voltage.For the lateral power MOSFET,the high breakdown voltage needs to be achieved by setting a long drift region,and the long drift region will increase the specific on-resistance of the device,thereby increasing the power consumption of the power MOSFET itself.Therefore,proposing different device structures and theories to improve the trade-off relationship between device breakdown voltage and specific on-resistance has always been one of the research hotspots in the field of power MOSFETs.The progress of semiconductor manufacturing technology has also brought about changes in the structure of lateral power devices.For example,in a quasi-vertical MOSFET,the bottom electrode is brought to the surface by introducing a buried layer,which combines the withstand voltage mode of a lateral device that is conducive to integration and a vertical device.Similarly,a lateral power device with a dielectric deep trench can fold the drift region around the dielectric deep trench,and the dielectric in the deep trench usually has a higher critical breakdown electric field.Therefore,the lateral size of this type of device can be greatly reduced,thereby reducing the specific on-resistance of the device and reducing the area of the chip occupied by the device.This paper takes the lateral power MOSFET(DT-MOSFET)with dielectric deep trench as the research topic,studies and analyzes the electric field concentration phenomenon in the drift region of the device caused by the parasitic capacitance effect in this type of device,and combines the existing process and technology puts forward some new device structures,which effectively eliminates this phenomenon.The innovative content of this article is arranged as follows.1.Propose and study a n-channel DT-MOSFET with resistive field plate.By adding a resistive field plate along the edge of the dielectric deep trench,the deep trench capacitance introduced by the dielectric deep trench is shielded,so that the drift region of the quasi-super junction design can achieve a good charge balance.Specifically,the MEDICI simulation software is used to simulate the withstand voltage,conduction,switching and other characteristics of the device.At the same time,the process realization of the device is theoretically demonstrated,and the process deviation in the key process steps of the device is analyzed and simulated.The results have been published in IEEE Journal of the Electron Devices Society(SCI,Q3),an important journal in the field of devices.2.Propose and study a p-channel DT-MOSFET with dual vertical linear variable doping regions.By adding a longitudinal linear variable doping region in the drift region on both sides of the dielectric deep trench to supplement the charge required by the deep trench capacitor,the electric field concentration phenomenon introduced by the parasitic deep trench capacitor in the drift region is eliminated,and the quasi super junction is adopted.The designed drift region achieves a good charge balance.In addition,the p-type variable doping region introduced into the drift region can increase the doping concentration in the side drift region,and the introduced n-type variable doping region can also increase the doping concentration of the drift region on the corresponding side through the charge compensation effect.The simulation shows that the breakdown voltage of the device is 440 V,and the specific on-resistance is 10.5 m?·cm~2.The results have been published in IEEE Transactions on Electron Devices(SCI,Q2),the top journal in the field of devices.3.Propose and study a p-channel lateral MOSFET with a combined dielectric deep trench.Based on the theory of deep trench capacitance,the combined dielectric deep trench is used to modulate the deep trench capacitor to make its capacitance value and the potential distribution of the drift region on both sides of the deep trench.By matching,turning the longitudinal variable doping region described in point 3 above into a uniform doping region can well supplement the charge required by the deep trench capacitor,thereby eliminating the electric field concentration phenomenon in the drift region.At the same time,because part of the high-k dielectric filling is used in the combined dielectric deep trench,the doping concentration of the deep trench capacitor charging charge compensation region is enhanced through the transfer electric flux mechanism,and the resistance of the drift region is further reduced.This achievement has been included in the Chinese core journal "Microelectronics".