Development And Fabrication Of 1-25A Avalanche Rectifier Diode

The development of modern science and technology has put forward higher requirements for the performance and its measurement standards of power devices.For example,avalanche tolerance is a new requirement for power rectifiers in recent years.The standard of avalanche tolerance is from DVR,?VF,I_PPM to avalanche power which can more accurately measure avalanche tolerance of diodes.In this thesis,aiming at the improvement of avalanche tolerance of 1-25A diode,a systematic study is conducted from theoretical design to practical fabrication.Firstly,the influence of longitudinal and terminal structures of the diode on the avalanche power is analyzed theoretically.The structure of the avalanche rectifier diode is determined to be p⁺pn^-n⁺non-through structure.Taking into account the actual process conditions and improving the process to make the bevel angle positive and the angle as large as possible.Secondly,on the basis of theoretical analysis,the longitudinal structure parameters of 1200V diode are optimized by Silvaco TCAD simulation software,and the device structure parameters are determined as follows:The surface peak concentration of p⁺region is5?10^{2 0}/cm³ and the width is 65 microns;the surface peak concentration of p region is5?10¹⁶/cm³ and the width is 55 microns;the doping concentration of base region is1.3?10¹⁴/cm³ and the width is 119 microns;the surface peak concentration of n⁺region is5?10^{2 0}/cm³ and the width is 30 microns.The characteristics of the positive bevel device are simulated.And then comparing with the characteristics of the negative bevel device.The simulation results are consistent with the theoretical analysis.Finally,the process experiment of the device is carried out.Through the analysis and study of the main process,the following improvements are made to the fabrication process of the general diode:firstly,the secondary diffusion process is changed into the primary diffusion process and a comparative experiment is carried out;secondly,the traditional sand blowing process is replaced by the electrolytic method of removing boron,phosphorus and silicon glass;thirdly,improved process is to achieve a positive bevel structure.Combining with simulation and comparing three different groups of experimental data,we can draw a conclusion:1)The p⁺pn^-n⁺non-through structure can improve avalanche power;2)The primary diffusion process can effectively improve avalanche power;3)The bigger the angle is,the higher the avalanche power will be.