Investigation On Variation Of Vertical Width Power VDMOS Devices

The conventional power MOS devices is limited by the"silicon limit",which is difficult to develop and apply in the field of high voltage and high current.Although the Superjunction（SJ）structural device breaks the"silicon limit"limitation between the on-resistance(R_on,sp)and the breakdown voltage（BV）,its performance is limited by the charge balance conditions.Although a novel structural device using High-k insulator（Hk）can overcome the influence of charge imbalance conditions,High-k insulator materials with a sufficiently large dielectric constant are required to make the overall performance close to SJ structural device's.Therefore,in order to improve the performance of devices,a novel Hk structural device and a novel Hk-SJ structural device are proposed in this paper.The main innovations of this paper are as follows:（1）According to the basic characteristics and shortcomings of conventional Hk structural devices,based on the optimization idea of electric field modulation,a Variation of Vertical Width Hk structure device is investigated in this paper.Which improve the electric field at the heterogeneous interface in the body by using trapezoidal High-k insulator,so as to optimize the electric field distribution and improve the overall performance.Analytic model of potential distribution and electric field distribution of the device is established by analytical calculation method,and the validity and correctness of the analytical model are verified by numerical simulation method.In addition,based on the electric field distribution analytical model,the approximate analytical model of the breakdown voltage is established by nonlinear fitting method.At the same time,the approximate analytical model of the on-resistance is established by the electric field approximation method.According to the theoretical analysis of the device analytical model and the verification of the numerical simulation experiment results,compared with the conventional Hk structural devices under the same range of breakdown voltage（BV=400V¹200V）,the specific on-resistance of the proposed device is reduced by about 9%³1%,and it has a better the R_on,sp-BV trade-off relationship.（2）According to the basic characteristics and shortcomings of conventional SJ structural devices,based on the optimization idea of electric field modulation,a Variation of Vertical Width Hk-SJ structure device is investigated in this paper.Which both overcome the influence of charge imbalance and improve the electric field at the heterogeneous interface in the body by using trapezoidal High-k insulator,so as to optimize the electric field distribution and improve the overall performance.In this paper,the numerical simulation method is used to analyze the influence of key parameters on the avalanche breakdown of the device and the influence of the breakdown voltage and on-resistance of the device.And comparative analysis of the performance of several similar devices.According to the results of numerical simulation experiments,for the same device cell size,the proposed device not only has high breakdown voltage,but also has lower on-resistance,and the related electrical characteristics are excellent,and the overall performance of the device is the best.