Characteristic Analysis Of Novel VDMOS With Electric Field Modulated By High K Insulator

Vertical double-diffused Metal Oxide Semiconductor(VDMOS)is an important power Semiconductor device,which is widely used in the fields of consumer electronics and industrial control because of its low switching power consumption and good frequency characteristics.Improving the contradictory relationship between breakdown voltage and specific on-resistance of devices has always been the focus of researchers The invent of superjunction devices breaks down the limitation of traditional silicon limit and greatly reduces the specific on-resistance of devices while increasing the breakdown voltage of devices.However,in the process of application,the doping concentration of N and P pillars in the drift region of the device needs to be highly consistent.Otherwise,the breakdown voltage performance of the device will be greatly reduced due to the influence of charge imbalance.On this basis,combined with the proposal of HK(High k)VDMOS device,a new device with high K material,the problem of charge imbalance in superjunction devices is solved.On this basis,combined with power device optimization process and field modulation technology,HK VDMOS devices are further optimized.The specific work of this paper includes:(1)on the basis of HK VDMOS device,the internal electric field distribution and the longitudinal electric field optimization idea were analyzed,and a new type of VDMOS device with stepped HK dielectric layer was proposed in combination with the idea of electric field modulation.This structure is mainly based on the traditional HK VDMOS device.By etching the HK dielectric layer on both sides of the drift zone and deposition of the dielectric layer with low dielectric parameters,graphical processing is carried out to form a new HK dielectric layer with the width changing along the vertical direction.Compared with traditional HK VDMOS devices,the electric field distribution at the bottom of the drift region is improved,and the breakdown voltage is improved to a certain extent.Through ISE simulation software analysis,under the condition that the length of drift region is 42?m,and the relative dielectric constant of drift region HK is 300,the breakdown voltage of step HK VDMOS device increases from 631 V to 736 V by about 20%,while the specific on resistance basically remains unchanged.At the same time,when the standard breakdown voltage of 600 V is reached,the relative dielectric constant of HK material required by HK VDMOS device needs to be more than 230,while for stepped HK VDMOS device,the relative dielectric constant of HK material only needs to be more than 120 to meet the requirement,and the dielectric constant of the material is reduced by 90%.(2)Step HK VDMOS device is established the mathematical model of electric field and electric potential distribution,the model established the step HK VDMOS device in different structural parameters and the electric field distribution in drift region,the relationship between the components of the electric field distribution with drift zone width,HK dielectric layer width,step height,doping concentration parameters such as the relationship between the expression of HK dielectric layer and explains the steps of the principle of the electric field modulation in drift region to the device.Combined with the analytical model and simulation software to analyze step HK VDMOS device research,verified the accuracy of the models,due to the drift of the device area on both sides of the HK dielectric layer thickness in the direction of the drift region is change,make the step in the electric field change of drift area,formed the new electric field peaks,thus by effect of electric field modulation makes in the drift region,the electric field distribution is more homogeneous,improves the compression performance of the device.