【作者】 廖伟；

【导师】 龚敏；

【作者基本信息】 四川大学 ， 凝聚态物理， 2001， 硕士

【摘要】 近年来新兴的碳化硅（SiC）半导体材料是第三代宽禁带化合物半导体材料的代表之一。它是唯一能够直接热氧化生长氧化层的化合物半导体，因此其器件工艺能够与现有的Si平面工艺相兼容，这使得SiC在制造高温、高频、高功率、高压和抗辐照MOS器件及相关集成电路方面无疑占有独特的地位。目前对SiC氧化层及其界面性质的研究已经成为SiC的热点研究课题之一。我们在本论文工作中使用干氧热氧化6H-SiC生长SiO₂层作为栅绝缘层，成功的制作出了SiC MOS电容，用以研究SiO₂／SiC系统的界面物理性质和辐照特性。 通过光照C-V测试技术，证实了p型SiC MOS结构的较大的平带电压漂移值并非是由于氧化层中的Al引起而应归因于大量界面态的存在。对测试中出现的有效界面态台阶现象进行了系统的理论分析和解释，得出了界面态台阶出现的必要条件以及利用界面态台阶估算有效界面态和氧化层固定电荷密度的方法。作为光照实验的补充，在低温实验中进一步验证了SiO₂／p-SiC界面态为施主型界面态并且有越靠近带边密度越高的趋势，而SiO₂／n-SiC界面态为受主型界面态，而且总体密度较SiO₂／p-SiC界面态低。 在正栅偏压条件下对SiC MOS电容进行了γ辐照，辐照剂量分别为0.2M和1.0M（SiO₂）。实验证实了SiC MOS电容具有比Si MOS电容更强的抗辐照能力，而n型SiC MOS电容又优于p型SiC MOS电容。通过对氧化层中的C，界面态的类型和禁带宽度三方面的讨论，对此进行了初步的分析。但是从界面态的角度来考虑SiC MOS器件，n沟道器件却具有比p沟道器件好得多的抗辐照能力。摘要（Abstraet） 最后，通过分析XPS测试结果中的SiZP和015的结合能谱峰，证实了Si衬底上热氧化生长的510:层的质量优于SIC衬底氧化生长的510:层.而SIMS测试分析Al、N和C元素的结果显示在p一SIC热氧化层中Al不易释放，且其中C的含量大于n一SIC氧化层.这表明5102/n一SIC界面质量优于5102/P一SIC界面，与C一V测试得到的结果是一致的.更多还原

【Abstract】 Silicon carbide (SiC) is one of the promising wide bandgap compound semiconductor materials. It is the only compound semiconductor whose native oxide is SiO2. This places SiC in a unique position to fabricate high-temperature, high-frequency, high-power, high voltage and radiation-hard MOS devices with standard silicon MOS techniques. The quality of oxide layer grown on SiC substrate and its interface properties are currently under intensive investigation. In this work, we have fabricated SiC MOS capacitors by oxidizing SiC substrates with dry Oa to form SiO2 layers as gate insulators and studied the physical and radiation induced properties of the SiOa/SiC interface system.The experiments indicated that the large flatband shift was due to the high density of interface states appearing at SiO2/p-SiC interface, rather than the aluminum that were incorporated into the oxide layer. The effective interface state ledge, which appeared in room temperature photo-CV curve, was systematically investigated. The basic conditions needed to observe this interface state ledge and the formulas to calculate the density of effective interface states and fixed oxide charges have been found. The low temperature experiments have showed that the interface states at SiO2/p-SiC interface were donor-type, while at Si02/n-SiC interface were acceptor-type.The SiC MOS capacitors were irradiated with 7 ray with different absorbed doses of 0.2 and 1.0Mrad(SiO2). Positive gate biases were applied during the irradiation. The results presented that SiC MOS capacitors had better irradiation tolerance than Si MOS capacitors and n-SiC capacitors were better than p-SiC capacitors. However, if the MOS devices were taken into account, n-channel would be much better than p-channel devices.XPS and SIMS analyses were also performed to investigate the properties of the oxides on p-type and n-type SiC substrate. The results of XPS measurementsshowed that the quality of SiO2 grown on SiC substrate was inferior to those grown on Si substrate. SIMS results indicated that there was no release of the aluminum incorporated into p-SiC oxides, and the concentration of carbon was higher than that in n-SiC oxides. Therefore, it could be determined that the quality of SiO2/n-SiC interface was much better than SiO2/p-SiC interface, Which also agreed well with the C-V results.更多还原