SiC肖特基势垒二极管的反向特性

在n型4H-SiC衬底上的n型同质外延层的Si面制备了纵向肖特基势垒二极管(SBD),研究了场板、场限环及其复合结构等不同终端截止结构对于反向阻断电压与反向泄漏电流的影响。场板(FP)结构有利于提高反向阻断电压,减小反向泄漏电流。当场板长度从5μm变化到25μm,反向阻断电压随着场板长度的增加而增加。SiO2厚度对于反向阻断电压有重要的影响,当厚度为0.5μm,即大约为外延层厚度的1/20时,可以得到较大的反向阻断电压。当场限环的离子注入区域宽度从10μm变化到70μm,反向阻断电压也随之增加。FLR和FP复合结构对于改善反向阻断电压以及反向泄漏电流都有作用,同时反向阻断电压对于场板长度不再敏感。采用复合结构,在10μA反向泄漏电流下最高阻断电压达到1 300V。讨论了离子注入剂量对于反向阻断电压的影响,注入离子剂量和反向电压的关系表明SBD结构不同于传统PIN结构的要求。当采用大约为150%理想剂量的注入剂量时才可达到最高的反向阻断电压而不是其他报道的75%理想剂量,此时的注入剂量远高于PIN结构器件所需的注入剂量。

Reverse Properties of SiC Schottky Barrier Diodes

Schottky barrier diodes(SBDs) were fabricated on Si-face of CVD-epitaxied layers on the n-type 4H-SiC substrate.The effects of different termination techniques,such as field plate(FP),field limiting ring(FLR) and their combination,on reverse blocking voltage and reverse leakage current were discussed.The FP structure is benefited to increase the reverse blocking voltage(VBR) and decrease the reverse leakage current(IR).When the FP length increases from 5 to 25 μm,the VBR increases.The thickness of the SiO2 film is important role for the VBR.When the thickness was 0.5 μm,namely about 1/20 the thickness of epitaxial layer,the larger VBR was obtained.The VBR increases when the ion implanted zone length of FLR increases from 10 to 70 μm.The composite structure of FLR and FP are effectively to improve VBR and IR,and the VBR is not sensitive to the FP length.The highest VBR reaches 1 300 V at 10 μA of leakage current with the composite structure.The effect of the ion implantation dose on VBR was also discus-sed.The relationship between the ion implantation dose and VBR indicates that there are differences between the traditional PIN diodes and SBDs.The highest VBR was obtained at about 150% ideal ion plantation dose,which is far higher than the plantation dose of PIN devices,but not 75% ideal ion plantation dose as reported by others.