SGT-MOSFET电场解析模型的建立

Analytically modeling electric field of shielded gate trench metal-oxide-semiconductor field effect transistor

屏蔽栅沟槽金属氧化物半导体场效应晶体管(SGT-MOSFET)在体内引入了纵向接源电极的屏蔽栅极,可以辅助耗尽漂移区,其耐压原理与沟槽MOSFET(VUMOSFET)不同.本文以110 V左右结构的SGTMOSFET为研究对象,通过数值仿真、理论分析以及解析建模,研究了不同结构的耐压原理以及结构参数与电场强度分布的相关性;建立了与器件各个结构参数相关的电场解析模型,为器件结构设计提供了理论依据;并引入雪崩载流子对小电流下的电场解析模型进行了修正,使得解析结果和仿真结果吻合较好;通过修正后的电场解析模型提取了最优电场下的场氧厚度,使得相应产品的静、动态特性得到明显改善,从而极大地提升了器件的性能.

Shielded gate trench metal-oxide-semiconductor field effect transistor(SGT-MOSFET)introduces a longitudinal shielding gate connected to the source inside the body,which can assist in depleting the drift region.Its principle of withstanding voltage is different from that of the vertical U-groove MOSFET(VUMOSFET).The SGT-MOSFET will generate two electric field peaks inside the body,which will further optimize the electric field strength distribution of the device and increase the breakdown voltage of the device.Therefore,SGT-MOSFET has not only the advantages of low conduction loss of CCMOSFET,but also lower switching loss.The effects of structural parameters such as the width of the mesa,the thickness of the field oxygen,the depth of the trench and the doping concentration on the electric field strength distribution of SGTMOSFET are not independent of each other.The more the parameters,the more complex the correlation of their effects on the electric field strength distribution is.In this paper,we take 110V SGT-MOSFET as a research object.Through numerical simulation,theoretical analysis and analytical modeling,the principle of withstanding voltage for different structures and the correlation between structural parameters and electric field strength distribution are studied.The analytical model of the electric field related to various structural parameters of the device is established,which provides a theoretical basis for the design of the device structure.The analytical model of electric field under low current is modified by introducing avalanche carriers,so that the modified analytical results can better match the simulation results.Through the modified electric field analysis model,the field oxygen thicknessin an optimal electric field is 0.68μm.Comparing with the product of SGTMOSFET with 0.58μm field oxygen thickness,at the optimal field oxygen thickness of 0.68μm,the onresistance of the device is reduced because the on-area of the device is increased;the electric field distribution is more uniform,so the device breakdown voltage increases;the gate-source capacitance decreases and the gatedrain capacitance is almost no change,so the gate-source charge decreases and the gate-drain charge is almost no change,while the total gate charge decreases.As a result,the optimal value parameter FOM1 of the device is increased by 18.9%,and the optimal value parameter FOM2 is reduced by 8.5%.Therefore,the static and dynamic characteristics of the device are significantly promoted,and the performance of the corresponding products is greatly improved.