4H-SiC pn Diode using Internal Ring(IR) Termination Technique

In this paper, the breakdown characteristic of 4H-SiC pn diode using Internal Ring(IR) termination technique is investigated. N-type 4H-SiC wafer having a 10um epilayer with a doping concentration of 5.4×10 15 /cm 3 was used to fabricate the pn diodes with one or two IRs. IR was formed by boron implantation of single energy of 360keV with 5×10 14 /cm 2 dose and activation annealing at 1700 o C for 30min in Ar ambient. In order to obtain an optimum breakdown voltage of pn diode with one or two IRs, the distance between p-base main junction and 1 st ring is varied from 3um to 7um and the distance between 1 st and 2 nd IR is fixed at 5um. A pn diode with two IRs termination structure has exhibited a high breakdown voltage of 1812V. Due to the IRs, the peak electric field at the interface between SiC and oxide of the surface is lower than the peak electric field at the edge of the 2 nd IR, which means that the breakdown of the device occurs at the edge of the 2 nd IR. Therefore the IR structure is attractive planar termination techniques for obtain a high breakdown voltage of 4H-SiC power device. Silicon carbide (SiC) is regarded as a promising semiconductor material for novel devices requiring high-power, high frequency, and high temperature operation owing to its electrical and thermal properties [1, 2]. In the case of high voltage devices, edge termination plays an important role in determining the breakdown voltage of the device. The mesa edge termination has been demonstrated to yield nearly ideal breakdown voltage for 6H-SiC pn diode. However, such an approach may not be attractive because of the nonplanar surface, which is difficult to passivate. Moreover, in case of 4H-SiC, ideal breakdown voltage could not be achieved using mesa edge termination [3]. For 4H-SiC, planar edge termination technique is more useful one rather than mesa edge termination. In this paper, the fabrication of 4H-SiC pn diode using IR edge termination is presented. The fabricated pn diode has an epilayer with doping concentration of 5.4×10 15 /cm 3 and a thickness of 10um. In our research, one and two IRs is used to improve the breakdown voltage. A cross-sectional view of the device is shown in figure 1. Single B + and multiple Al + implantations were carried out at 650 o C to form …