Application Of Two-dimensional Charge Coupling Effect In Power Semiconductor Devices

The two-dimensional charge coupling is the transverse and longitudinal two-dimensional electric field effect produced by the depletion layer in vertical and horizontal directions respectively.When it is introduced into power semiconductor devices,the coexistence of high voltage resistance and low on-resistance can be realized and the silicon limit can be broken.The two-dimensional charge coupling effect is often applied in the form of super junction in unipolar power semiconductor devices,such as power MOSFET and JBS diodes.This paper mainly studies the high voltage withstand principle,super junction JBS diode characteristics and super junction VDMOS characteristics of two-dimensional charge-coupled devices(super junction power devices),and proposes optimization methods.The specific research contents are as follows:Firstly,Silvaco Atlas software was used to build a two-dimensional charge-coupled structure model of the super junction.On the basis of theoretical analysis,Silvaco simulation was used to analyze the working principle of the super junction power device.Because of the transverse charge coupling effect,the longitudinal electric field distribution tends to be rectangular,and the super junction two-dimensional charge coupling structure can withstand high reverse voltage under high doping,thus breaking the "silicon limit".Through the simulation of transverse and longitudinal electric field distribution in the device under reverse bias voltage,three electric field peaks exist at the PN junction are obtained.By adding buffer layers on both sides of the super junction,the electric field distribution can be optimized more effectively,and the two-dimensional charge coupling structure model of the semi-super junction can be established.The structure parameters of semi-super junction are simulated,which lays a foundation for its application in other power devices.Secondly,the super junction structure is introduced into the JBS diode,and the initial structural parameters of the super junction JBS diode are designed.Silvaco software was used to model the P column structure of super junction JBS diode with uniform distribution and Gaussian distribution respectively,and the influence of P column depth,width and doping concentration on the forward characteristics,reverse recovery characteristics,reverse voltage resistance characteristics and noise was simulated.The influences of each parameter on on-state,on-block state and on-to-block transition state are obtained.Thirdly,the super junction structure is introduced into the vertical double diffusion VDMOSFET,and the initial structural parameters of the super junction MOSFET are designed.Using Silvaco software,the initial structure model of super junction MOSFET was first established.Super junction MOSFET is to change the N-drift region of traditional MOSFET into P column and N column periodic arrangement and optimize the width and doping concentration of the drift region.The internal structure and doping distribution of MOSFET cells can be clearly observed through the simulation model.Using this model,the transfer characteristics,current-voltage characteristics and voltage withstand characteristics of super junction MOSFET are simulated and analyzed respectively.In the transfer characteristics,the relationship between the threshold voltage and the sub-threshold amplitude of the super junction MOSFET and the doping concentration of the P-base region is analyzed.The current-voltage characteristics are similar to those of traditional MOSFET,which can be divided into linear region,nonlinear region and saturated region.With the increase of leakage voltage,the vertical depletion layer in the drift region becomes wider to block the breakdown electromotive force.The distribution of the breakdown electric field inside the cell is discussed and compared with MOSFET to obtain the breakdown point.On this basis,the influence of P column height and doping concentration on the voltage resistance is also discussed.In conclusion,the advantages of the super junction device in high voltage resistance and other aspects are obtained by comparing the super junction device with the traditional device.