【作者】 马永吉；

【导师】 张义门；

【作者基本信息】 西安电子科技大学 ， 微电子学与固体电子学， 2009， 硕士

【摘要】 本论文对Ni/4H-SiC SBD和MESFET的辐照效应进行了分析。重点研究了辐照引入的陷阱对这两种器件的影响。通过SBD的仿真,发现材料中的陷阱会导致正、反向电流的减小。从MESFET的仿真中可以看出,由于沟道掺杂浓度较大,器件可以承受更多的辐照引入的陷阱。制备了Ni/4H-SiC肖特基势垒二极管（SBDs）和欧姆接触TLM测试图形,并进行了高能电子辐照实验。电子能量为1MeV,最高剂量为3.43×10¹⁴e/cm²。辐照后器件在2v下的正向电流下降幅度约50%;在-200V下的反向电流上升幅度小于30%。辐照后,0V偏压的器件的势垒高度（φ_B）从1.20eV增加为1.21eV,-30V偏压下的势垒高度从1.25eV下降为1.19eV。通过对常温下退火效应的观察,φ_B的退化是由肖特基界面态的变化造成的。串联电阻（Rs）和反向电流随着辐照剂量的增加而增加,这是由于电子在SiC材料中引入辐照缺陷造成的。Ni/SiC欧姆接触的比接触电阻（ρ_c）辐照后从5.11×10^-5Ωcm²上升为2.97×10^-4Ωcm²。本文对制备的Ni/4H-SiC肖特基势垒二极管（SBD）进行了γ射线辐照实验,并在辐照过程中对器件分别加0V和-30V偏压。经过1Mrad（Si）总剂量的γ射线辐照后,不同辐照偏压下的Ni/4H-SiC肖特基接触的势垒高度和理想因子都没有退化,SiC外延层中的少子寿命也没有退化。辐照后器件的反向电流下降,这是由于器件表面的负界面电荷增加引起的。本文的研究结果表明辐照偏压对Ni/4H-SiC SBD的辐照退化效应没有明显的影响。通过实验以及仿真数据可以发现,Ni/4H-SiC SBD在经过3.43×10¹⁴e/cm^-2剂量的电子辐照后,肖特基势垒高度有少许变化,常温退火一周即回到原值。最主要的变化是陷阱效应导致的串联电阻增加,这种辐照效应在常温下退火一周后仍不能完全恢复。而1Mrad（Si）总剂量的γ射线辐照对Ni/4H-SiC SBD影响很小。这些实验数据说明我们的Ni/4H-SiC SBD具有良好的抗辐照特性。更多还原

【Abstract】 The radiation effect of the Ni/4H-SiC SBD and MESFET were studied in this thesis. The influence of the traps induced by irradiation on their characteristics were focused. In the SBD’s simulation, traps in the material make the forward current and reverse current decreased. In the MESFET’s simulation, we found that it can withstand more traps in the material induced by irradiation due to the higher impurity concentration in the channel.The Ni/4H-SiC Schottky barrier diodes （SBDs） and TLM （Transfer Length Method） test patterns of Ni/4H-SiC ohmic contacts were fabricated, and irradiated with1Mev electrons up to a dose of 3.43×l0¹⁴e/cm^-2.After radiation, the forward currents of the SBDs at 2v decreased by about 50%, and the reverse currents at -200v increased by less than 30%. Schottky barrier height （φ_B） of the Ni/4H-SiC SBD increased from 1.20ev to 1.21ev under Ov irradiation bias, and decreased from 1.25ev to 1.19ev under -30v irradiation bias. The degradation ofφ_B could be explained by the variation of interface states of Schottky contacts. The on-state resistance （Rs） and the reverse current increased with the dose, which could be ascribed to the radiation defects in bulk material. The specific contact resistance （ρ_c） of the Ni/SiC ohmic contact increased from 5.11×10^-5Ωcm² to 2.97×l0^-4Ωcm².The Ni/4H-SiC Schottky barrier diodes（SBDs） were irradiated with the ⁶⁰Co gamma-ray source to the accumulated dose of 1Mrad（Si）.0v and -30v bias voltages were applied to the SBDs during irradiation. After 1Mrad（Si） radiation, Schottky barrier height and ideality factor of the Ni/4H-SiC SBDs under different bias voltage basicly remain the same values, and minority carrier lifetime of the epitaxial layer also has nodegradation.The reverse current decreases after radiation, which can be explained by the negative surface charge increase. The results show radiation bias voltage has little influence of gamma-ray on the Ni/4H-SiC SBD.Through testing and simulation data, we found after radiation with 1MeV electrons up to a dose of 3.43×10¹⁴e/cm^-2,the Schottky barrier height changed slightly and recovered with annealing at room temperature for a week. But Rs didn’t recover after a week.1Mrad（Si） gamma-ray radiation hardly change the Ni/4H-SiC SBD’s characters. These data show that 4H-SiC SBDs have excellent capability of radiation hardness.更多还原