The Research On New Structure Of High Voltage LDMOS Based On Variable-K Materials

The emergence of metal oxide semiconductor field effect transistors(MOSFETs)has made the development of integrated circuits(ICs)a new process.As the core device of integrated circuits,lateral power MOS(Metal Oxide Semiconductor)has become an increasingly growing object.According to the doping type of drift region,it can be divided into pLDMOS and nLDMOS.This article is based on the two types of lateral double-diffusion devices,using the device's reduced surface electric field technology(RESURF),dielectric field enhancement ENDIF(ENhanced DIelectric Field)technology and the impact of dielectric materials on the device to design a High-K Dielectric trench and the structure of the trench type LDMOS device with different dielectric materials,and study its structural characteristics and mechanism analysis.Two different high-voltage variable-K materials LDMOS devices not only make the conventional pLDMOS have RESURF effect and solve the problem of substrate leakage,but also alleviate the contradictory relationship between BV and Ron,sp of pLDMOS and nLDMOS devices.(1)Propose a new structure of HK SOI pLDMOS(High-K Silicon On Insulator pLDMOS).The structure is to add lateral High-K dielectric trenchess in pLDMOS.The High-K dielectric trench has the ability to assist in depleting the drift region,thereby increasing the concentration of the drift region and reducing the specific on-resistance in the on state.In the off-state,the High-K medium internally generates polarized charges and ionized charges in the drift region to maintain charge balance,optimize the field distribution in the device,and thus improve the withstand voltage.At the same time,adding a High-K dielectric trench in pLDMOS makes the device produce RESURF effect.Using the principle of self-adaptive generation of polarized charge in High-K dielectrics,two types of equations in the medium are solved by zone to obtain the two-dimensional electric potential and electric field distribution of the new material in the SOI device,and the quantitative analysis of its two-dimensional field modulation is achieved.Obtain the device potential field model,and use the model to optimize some device structure parameters to guide the device design.The software simulation results show that the BV of the new structure of HK SOI pLDMOS is-518 V,and Ron,sp is 1.425?·cm2.Finally,the technical scheme and layout of the new device are developed.(2)Proposed VK DT LDMOS(Variable-K Deep Trench LDMOS)structure.The structure uses three dielectric materials,namely High-K dielectric,low-K dielectric and SiO2 material to design the dielectric trench device structure.The addition of trench technology not only has a significant effect on shortening the size of the drift region of the device and reducing the on-resistance,but also greatly reduces the design area of the chip.Compared with the traditional oxidation bath,the low-K dielectric material is added to the surface of the device to increase the surface electric field in the structure using ENDIF technology.The addition of variable-k materials in the drift region introduces a new electric field peak into the device body and optimizes the electric field in the body.A thin High-K material column is introduced on the left between the trenches,which effectively increases the doping concentration of the entire drift region and maintains charge balance with the ionized charge in the drift region.Thus,the breakdown voltage of the device is increased.According to the simulation results of software:VK DT LDMOS has a BV of 267 V and a Ron,sp of 7.627 m?·cm2 at a length of only 6.5 ?m,and the figure of merit(Figure Of Merit,FOM=BV2/Ron,sp)is 9.347 MW·cm-2.Furthermore,the layout preparation scheme and process design flow of the new structure of variable-K trench LDMOS are proposed.