| Fast and soft recovery diodes(FSRD)are often used in an anti-parallel way with the main switching device in the actual circuit to provide a freewheeling loop for the load.With the continuous improvement of the performance of the main switching device,higher requirements are also placed on the fast and soft recovery diode.Not only its high voltage,low loss and soft recovery,but also strong resistances to dynamic avalanche is required to improve the reliability of device under overstress conditions.By taking 6.5kV FSRD as an example,the operation mechanism,static and dynamic characteristics of a diode with Bilateral Adjustment Region(BAR)are studied in this paper.The characteristics of BAR diode,conventional diode(p+pn-nn+,CD),emitter short diode(ESD)and field charge extraction(FCE)diode are compared by conducting the simulated analysis with Sentaurs-TCAD.The influences of temperature and key structural parameters on the blocking,conduction,surge,forward recovery and reverse recovery characteristics of BAR diodes are discussed,the optimized structural parameters 'are extracted,and the process is analyzed.The main research contents are as follows:Firstly,the blocking,conduction,forward recovery and reverse recovery mechanisms and its parasitic effect of the BAR diode are studied.The conditions for conducting the parasitic npn transistor on the anode and pnp transistor on the cathode sides of the BAR diode during reverse recovery are analyzed,the results show that npn transistor and pnp transistor conduction can inhibit the peak electric field strength at pn-junction and n-n junction during reverse recovery,respectively.Secondly,the dynamic and static characteristics of BAR and CD,ESD,FCE diodes are compared.In this paper,it analyzes the influences of temperature on mobility,carrier lifetime and intrinsic carrier concentration,as well as the static and dynamic characteristics of BAR diode at different temperatures.And moreover,it also studies the influences of temperature on the efficiency of electron and hole injection during the conduction of parasitic npn and pnp transistors.The results show that the BAR diode improves the reverse recovery softness of CD and ESD and the reverse recovery speed of FCE diode.Meanwhile,The increase in temperature will reduce the peak electric field at the pn-junction and n-n junction during reverse recovery.Thirdly,the characteristics of BAR diode are optimized,the influence of the key structural parameters of BAR diode on the characteristics is analyzed.The results show that the width of the n+adjustment region,the concentration the thickness of the p buffer layer are sensitive parameters that affect the characteristics of the device,and the optimized parameter values are given.Finally,the process flow of BAR diode is studied,the corresponding process conditions are determined through process simulation.The research results can provide some reference for the research and development of high voltage fast and soft recovery diode. |
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