【作者】 王超；

【导师】 庄大明；

【作者基本信息】 清华大学 ， 材料加工工程， 2003， 硕士

【摘要】 介电膜，是一种重要的电子薄膜。在微电子技术和光电子技术中有着广泛的应用。随着电容器件集成度越来越高，以SiO2为主的介质膜接近极限厚度，难以满足要求。氧化钽薄膜(Ta2O5)因为具有高介电常数和良好的热、化学稳定性，成为最有希望获得实际应用的介电膜。本文主要研究了氧化钽薄膜的制备、电学性能以及改善性能的途径。论文采用自行组装的中频交流磁控溅射设备制备了氧化钽薄膜，考察了溅射气体中氧气含量、基底温度等对薄膜成分、结构的影响，并且通过优化工艺参数得到了接近化学计量比的氧化钽薄膜。研究了薄膜的沉积特性。分析了溅射气体中氧气含量和薄膜厚度对折射率的影响及机理。本文重点研究了Ta2O5薄膜的电学性能。分析了介电材料的导电机制和击穿原理，并对氧化钽薄膜的导电机制进行测试和研究。结果显示，随着场强的增加，导电机制分别以欧姆定律、肖特基效应、普尔－弗兰凯尔效应，和F-N为主，最后发生F-N击穿。研究了氧气含量、薄膜缺陷、基底粗糙度等因素对氧化钽电学性能的影响。测试得出薄膜的介电常数为20~30之间(10~20kHz)，介质损耗因数为0.001(20kHz)。氧化钽薄膜的最佳性能为：当上电极直径为1mm时，击穿强度为2.22MV/cm，漏电流密度在0.5MV/cm低于1×10-8A/cm2；当上电极直径为0.5mm时，击穿场强达到4.0MV/cm，高于文献报导的最高值3.8MV/cm。 本文还采用减小上电极面积和对基底进行预处理两种方法，制备了具有高击穿场强和低漏电流密度的MIM单元结构，提高了成品率。研究发现，随着MIM结构上电极面积的增大、基底粗糙度增大，MIM的电学性能变差，成品率降低。对溅射态的薄膜进行了阳极氧化后理，通过对比试验发现，阳极氧化可以起到填补微孔和使Ta原子充分氧化的作用，增加薄膜的击穿场强，提高薄膜的绝缘性能。更多还原

【Abstract】 Dielectric thin film was an important kind of electronic thin films, which has wide applications in microelectronic and photo-electronic technology. With the demands of large integration of capacitors, Silicon Oxide (SiO2) has approached its thickness limitation. Tantalum Oxide (Ta2O5) attracts more attentions because of its high dielectric constant, stable thermal and chemical properties. It might become the most promising candidate high constant dielectric thin films applied in industries. The dissertations focus on the preparation, electrical properties of Ta2O5 and how to improve its insulation properties. Tantalum oxide films were prepared by self-assembled middle frequency a.c. sputtering system. The contents and microstructure of the films were studies as the functions of oxygen percentage in sputtering gases and substrate temperature. The stoichiometric films were prepared by optimizing processing parameters. The deposition characteristics were studied. The effects and mechanisms of oxygen percentage and thickness on the refractive constant were analyzed. The work mainly focuses on the study of electrical properties of Ta2O5. The conduction and breakdown mechanism of the films were tested and studied. The results showed that with the increase of the field strength, the conduction of the films was separately dominated by Ohm’s Law, Schottcky Effect, Pool-Frenkel Effect, and Fowler-Nordheim tunneling breakdown. The electrical properties as the function of oxygen percentage, defects in the films, and the roughness of the substrate surface were investigated. The dielectric of the films was 20~30 (10~20kHz), the dielectric loss tangent was 0.001(20kHz). The best result was obtained: the breakdown field was 2.22MV/cm, and the leakage current density was lower than 1×10-8A/cm2 with the top electrode of<WP=9>1.0mm in diameter; The highest breakdown field was 4.0MV/cm with 0.5mm in diameter, which was higher than 3.8MV/cm reported in other references by the same method.The MIM structure of high quality was fabricated by reducing the area of top-electrode and pretreatment on substrates, and the yield was also improved by these two methods. The electrical properties become worse and yield degraded with the larger top-electrode area and rougher substrate.The as-deposited tantalum oxide films were post-processed by anodic oxidation. The micropores in the films were filled and Ta atoms were fully oxidized compared to as-deposited films. In addition, these films exhibit greatly improved leakage currents and breakdown field strength.更多还原