The Design And Parameter Optimization Of100A/1200V Si JBS Device

As a novel complex diode, Junction Barrier Controlled Schottky Rectifier has the advantagesof larger current capacity, higher breakdown voltage, faster switching speed and higher surgecurrent resistance.The main work of his paper is to design a Si JBS with on state current of100A andbreakdown voltage of1200V which can be manufactured by the SCR fabrication process.Based on the operational mechanism of JBS and the SCR fabrication process, the mainmaterial parameters and structure parameters are pre-assumed. In order to obtain higherbreakdown voltage, the field limiting ring structure is adopted. Through solution of the Poissonequation in cylindrical coordinate system, the spacing and number of the field limiting rings hasbeen deduced. The results of the electrical characteristic simulation of the silicon JBS devicesinitial structure obtained by simulation with SILVACO TCAD Atlas indicate that breakdownvoltage of the initial structure does not meet the design requirements.In order to improve the breakdown voltage, reduce the error introduced by the abruptjunction approximation, an assumption has been made that the double mass diffusion junctionconsist of two linearly single-side gradual junction. Then, the electrical characteristic of thedouble mass diffusion junction is studied. The simulated results with SILVACO TCAD Atlas onthe advanced Si JBS structure show that the breakdown voltage was improved even though it canstill not meet the design requirements. To further optimize the structure, three kinds ofimprovement schemes has been put forward:1)decrease the concentration of the N-drift,2)increase the depth of the junction,3)add N+stoping ring or N+field stopping ring.By adopting the last2improvement schemes respectively, the breakdown voltage of the SiJBS structure has been elevated up to more than1400V with the junction depth respectively of50μm and30μm, number of the field limiting ring respectively of2and3. As a result,7kinds ofSi JBS structures in total were designed which meet the design requirements in breakdownvoltage index.Then,2kinds of Si JBS structures of all had been selected corresponding to the2kinds ofjunction depth each as the last schemes. Their forward characteristics and transient characteristicswere simulated and tested with SILVACO TCAD Atlas after the virtual samples were fabricatedwith SILVACO TCAD Athena respectively. By using the field limiting ring structure, the field limiting ring spacing are required the sameeverywhere, thus circular and hexagonal layout are put forward. After comprehensiveconsideration, the regular hexagon layout has been adopted. The calculation of the parameter ofthe layout corresponding to the selected two kinds of silicon JBS device structure has been done.Then, SILVACO TCAD Atlas was used to test the electrical characteristics of the samples. Testingresults indicate that although there is a certain degree of degradation in breakdown voltage,current density and switching speed of the two kinds virtual test samples of silicon JBS device,the design requirements are still met.Two kinds of Si JBS structures suitable for SCR fabrication process has been designed withthe junction depths of50μm and30μm respectively, of which the breakdown voltages are1440Vand1470V and the turn-off times are12.5ns and5ns respectively. The forward currents of bothare100A above.