The Study Of 4H-SiC Junction Barrier Schottky Diodes And Ion Implantation At Room Temperature

As one of the representative of the third generation semiconductors,SiC possesses many excellent physical properties comparing with Si,which shows promise in applications of high-power,high-frequency,high-temperature electronic and optoelectronic devices.Nowadays,SiC has been used to prepare Schottky barrier diodes?SBD?,pin diodes and junction barrier Schottky diodes?JBS?.Among these power devices,SiC JBS is studied a lot for its combination of the advantages of SBD and pin.Currently,the study of JBS focuses on the ion implantation and junction termination technology.In this letter,A1 ion implantation depth and concentration distribution in n type 4H-SiC have been systematically simulated as functions of tilt angle,buffer layer,and implantation energy and dose.Al ion implantation condition with multiple energies and doses were designed and performed at room temperature to obtain an uniform ion concentration distribution with a depth of 500 nm.The Al ions were activated by annealing at 1650? and 1750? where the samples were covered by SiC wafers to protect the surface.The effect of annealing temperature on activation was investigated.The influences of implantation condition and SiC wafer protection on the surface roughness of SiC were also investigated.After activation,Ni was deposited on the Al-implanted p-SiC to form ohmic contact,on which the effect of activation concentration was studied.The damage induced by implantation,surface roughness after annealing and activation effect were characterized by Raman spectrum,atomic force microscopy?AFM?and hall test,respectively.The results show that a p-SiC with surface roughness of 0.862 nm and active concentration of 4.25×1019 cm-3 can be obtained employing tilt angle of 4°,100 nm thick SiO₂ buffer layer,annealing temperature of 1750? and surface protection by covering SiC wafers.These results will be useful for the design of SiC based devices including Pin diodes,JBS,MOSFET,JFET,and BJT.The optimum condition of Ohmic contact annealing has been finded at the temperature of 1050? and hold the temperature for 2 minutes.Through the simulation of ion implantation and field limiting rings,the parameters can be confirmed.With the addition of field plate,a JBS diode whose threshold voltage is IV,breakdown voltage is 1300V,ideality factor is 1.49 and barrier height is 1.07eV has been fabricated.