【作者】 尚也淳；

【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， 2001， 博士

【摘要】 目前SiC作为一种在抗辐照领域有着巨大应用前景的极端电子学材料而倍受人们关注。为了能充分发挥SiC抗辐照的优势和潜力，本文首先对SiC区别于常规半导体的特性作了系统的研究： 用单粒子Monte Carlo方法研究了6H-SiC的电子输运规律，模拟的结果体现了6H-SiC具有良好的高温和高场特性以及迁移率的各项异性，其横向迁移率和纵向迁移率相差近5倍。模拟结果和实验数据的对比说明了对6H-SiC输运特性的模拟是正确的。 把Frenkel-Pool效应引入了对SiC MOS表面空间电荷区杂质不完全离化的分析，并建立起了在电场作用下SiC杂质离化的新的模型。分析的结果表明，电场的作用会使析冻效应减弱。文中还提出了一个新的SiC MOSFET反型层薄层电荷数值模型。对于SiC MOSFET，杂质不完全离化的影响主要在亚阈区。 在辐照的位移效应方面： 从理论上对电子辐照在4H-SiC中引入的缺陷数量和各种缺陷能级进行了计算和分析，其中只有EH6/EH7缺陷能级在SiC中起着有效的复合中心的作用。采用了SRH模型来估计电子辐照下4H-SiC的少子寿命，并最终给出电子辐照下4H-SiC少子寿命损伤系数的模型。结合具体的试验条件，证明了所得出的电子辐照4H-SiC少子寿命损伤系数的模型是合理的。 对SiC JFET的电参数如电子浓度，迁移率，电阻率和空间电荷区密度在中子辐照下的变化进行了分析，提出了中子辐照下6H-SiC JFET的器件模型，利用此模型对SiC JFET在室温和300℃时的辐照响应进行模拟的结果和实验值相符。 提出了中子辐照下SiC pn结电特性退化的新的理论，pn结耗尽区中的辐照陷阶在耗尽区电场的作用下热发射效应得到加强，从而导致pn结正偏和反偏时的复合电流和产生电流的改变。推导了辐照后SiC pn结理想因子与外加电压的关系，并给出了SiC pn结中子辐照电特性退化的模型，从而很好解释了SiC pn结辐照后出现的电特性退化的现象。 在辐照的电离效应方面，研究了辐照在SiC MOS氧化层中引入的陷阱电荷对MOS沟道反型层迁移率的影响。 先推导了一种SiC反型层表面粗糙散射的指数模型，研究证明应用此模型能够更精确地研究SiC MOS沟道载流子的输运规律。当有效横向电场较低时，库仑散射在SiC反型层的电子输运中起主要散射作用，而当有效横向电场升高时，表面粗糙散射的作用会变得愈来愈显著。 接着在尺寸量子化的条件下，提出了一种综合的SiC反型层库仑散射的解析 SIC材料和器件特性及其辐照效应的研究模型，该模型考虑了栅氧化层电荷、界面态电荷、沟道电离杂质电荷的作用以及它们之间的相关性。对6H－SIC反型层迁移率进行的Monie Caro模拟结果表明，库仑中心的相关性，库仑电荷量及电荷中心和 SIC侣。界面之间的距离都对SICMOS沟道迁移率产生着影响。 在实验上首次对6H－SIC MOS结构的电特性及其辐照引起的电参数退化进行了研究，结果说明：在氧化层电场较高时是Fowler－Nordheim隧穿电流决定着SICMOS结构的漏电流。当氧化层中存在较强电场时，电离辐照对S汇 MOS电容的影响会更明显，SIC MOS器件比 St器件具有更好的抗 Y辐照的能力。更多还原

【Abstract】 The attractive characteristics and the excellent electric properties of SiC has led us to the fabrication of electronic devices used in strong radiation environments. For the application of SiC devices to radiation fields, it is important to know the irradiation effects and characteristics of SiC materials and devices. The main contributions in this thesis are as following:Temperature- and electric field-dependent electron transport in 6H-S1C is studied by single-particle Monte Carlo technique. The physical model used in the simulation is developed considering the main scattering mechanisms in details. The results show the excellent high-temperature properties and anisotropy of mobility. The ratio Au盠./p~ in 6H-SiC is about 5. The simulated results are in good agreement with measured data in a wide range of temperature and electric field.The influence of incomplete ionization of impurity in 6H-SiC on MOSFET electrical characteristics is investigated considering the Frenkel-Pool effect, Which can enhance the impurity ionization by lowing the effective barrier height. And a new numerical Charge-Sheet model for SiC MOS inversion layers is presented based on an numerical solution of a one-dimension Poisson equation. The results obtained from this approach are in good agreement with the measured values. The study shows that the impact of incomplete ionization on SiC MOSFET is more notable in subthreshold region than in strong inversion region.The total number of defects induced by electron irradiation in 4H-SiC is calculated theoretically. The deep level defect of EH6/EH7 is considered to play the most important role in carrier recombination from the comparison of all kinds of possible electron traps. A model of the minority carrier lifetime damage constant is presented. The model is proved to be reasonable by good match with experimental data.In respect of SiC devices, an analytical model of 6H-SiC JFET to well match the experimental results is proposed. The radiation response of SiC JFET in room temperature to 300 C is simulated with the analysis for the neutron irradiation effect such as carrier removal, mobility degradation and space charge density decrease. The degradation of the electrical characteristics in SiC pn junctions irradiated by neutron is attributed to the recombination centers and the electric field effect on the thermal emission of traps within the depletion region. The relationship of the ideality factor to the applied voltage is theoretically studied. A model of the SiC pn junctions irradiated by neutron is presented.The effects of radiation induced oxide trapped charge and SiC/Si02 interface state density on inversion layer mobility is studied systematically. Firstly, a new interface roughness scattering model is developed using exponential autocovariance functions. The simulation results show that the electron mobility calculated using the exponential model are in good agreement with the experiment data. Then, a comprehensive an~tlyticai model for coulomb scattering in 6H-SiC inversion layers is presented considering all the coulomb effects of the charged-centers near the SiCISiO2 interface. This model takes into account the effects of the charged-centers correlation. Finally, the electron mobility in 6H-SiC inversion layers is studied by single-particle Monte Carlo technique. The simulation results fit the experimental data very well. The study shows that coulomb scattering becomes more important at low transverse-electric field and both the density and the distribution of charged-centers play an important role in electron transport in SiC inversion layers.The radiation response and electric characteristics of 6H-SiC MOS structure is studied with experiment for the first time. It is found that the main electronic conduction mechanism in the high field regions of the I-V characteristics is identified to be FowlerNordheim tunneling. The effect of y ray on SiC MOS C-V characteristics depends strongly on the bias voltage applied to the gate elec更多还原