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首页> 外文学位 >Fabrication and characterization of oxide-based thin film transistors, and process development for oxide heterostructures.
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Fabrication and characterization of oxide-based thin film transistors, and process development for oxide heterostructures.

机译：氧化物基薄膜晶体管的制造和表征，以及氧化物异质结构的工艺开发。

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This dissertation is focused on the development of thin film transistors (TFTs) using oxide materials composed of post-transitional cations with (n-1)d 10ns0 (n≥4). The goal is to achieve high performance oxide-based TFTs fabricated at low processing temperature on either glass or flexible substrates for next generation display applications. In addition, etching mechanism and Ohmic contact formation for oxide heterostructure (ZnO/CuCrO 2) system is demonstrated.;The deposition and characterization of oxide semiconductors (In 2O3-ZnO, and InGaZnO4) using a RF-magnetron sputtering system are studied. The main influence on the resistivity of the films is found to be the oxygen partial pressure in the sputtering ambient. The films remained amorphous and transparent (> 70%) at all process conditions. These films showed good transmittance at suitable conductivity for transistor fabrication.;The electrical characteristics of both top- and bottom-gate type Indium Zinc Oxide (InZnO) and Indium Gallium Zinc Oxide (InGaZnO4)-based TFTs are reported. The InZnO films were favorable for depletion-mode TFTs due to their tendency to form oxygen vacancies, while enhancement-mode devices were realized with InGaZnO4 films. The InGaZnO4-based TFTs fabricated on either glass or plastic substrates at low temperature (100°C) exhibit good electrical properties: the saturation mobility of 5--12 cm2.V-1.s-1 and threshold voltage of 0.5--2.5V. The devices are also examined as a function of aging time in order to verify long-term stability in air.;The effect of gate dielectric materials on electrical properties of InGaZnO 4-based TFTs was investigated. The use of SiNx film as a gate dielectric reduces the trap density and the roughness at the channel/gate dielectric interface compared to SiO2 gate dielectric, resulting in an improvement of device parameters by reducing scattering of trapped charges at the interface. The quality of interface is shown to have large effect on TFT performance.;Plasma etching process of ZnO was carried out using a variety of plasma chemistries: CH4/H2-, C2H6/H 2-, Cl2-, IBr-, ICl-, BI3- and BBr3/Ar. High fidelity pattern transfer can be achieved with practical etch rate and very smooth surface in methane-based chemistries, although the sidewall is not completely vertical. Threshold energy as low as 60 +/- 20 eV for all plasma chemistries was achieved, confirming that etching is driven by ion-assisted mechanism over the whole range of ion energy.;Ohmic contacts to p-CuCrO2 are examined using borides (CrB2 and W2B5), nitrides (TaN and ZrN) and a high temperature metal (Ir). These materials are used as a diffusion barrier in Ni/Au based contacts, i.e., Ni/Au/X/Ti/Au metallization scheme, where X is the refractory material. A minimum specific contact resistance of ∼ 5x10 -4 O.cm2 was achieved for the Ir-containing contacts after annealing at temperature of 500--800°C for 60s in O2 ambient. The presence of Ir diffusion barrier increase the thermal stability of the contacts by ∼ 200 °C compared to conventional Ni/Au contacts. By sharp contrast, the use of other refractory materials led to the poorer thermal stability, with the contact resistance increasing sharply above 400°C.
机译：本文的研究重点是使用由后过渡阳离子（n-1）d 10ns0（n≥4）组成的氧化物材料开发薄膜晶体管（TFTs）。目标是在下一代处理应用的玻璃或柔性基板上实现在低处理温度下制造的高性能氧化物基TFT。另外，对氧化物异质结构（ZnO / CuCrO 2）体系的腐蚀机理和欧姆接触的形成进行了研究。研究了利用射频磁控溅射系统沉积和表征氧化物半导体（In 2O3-ZnO和InGaZnO4）的特性。发现对膜电阻率的主要影响是溅射环境中的氧分压。在所有工艺条件下，薄膜均保持非晶态和透明性（> 70％）。这些膜在适合晶体管的导电性下显示出良好的透射率。报道了基于顶栅和底栅型氧化铟锌（InZnO）和基于铟镓锌氧化物（InGaZnO4）的TFT的电学特性。由于InZnO薄膜倾向于形成氧空位，因此它们对耗尽型TFT有利，而用InGaZnO4薄膜实现增强型器件。在低温（<100°C）下在玻璃或塑料基板上制造的基于InGaZnO4的TFT具有良好的电性能：饱和迁移率为5--12 cm2.V-1.s-1，阈值电压为0.5-- 2.5V。还检查了这些器件与老化时间的关系，以验证其在空气中的长期稳定性。;研究了栅极介电材料对InGaZnO 4基TFT的电学性能的影响。与SiO2栅极电介质相比，使用SiNx膜作为栅极电介质可降低阱密度和沟道/栅极电介质界面处的粗糙度，从而通过减少界面处俘获电荷的散射来改善器件参数。界面质量对TFT性能有很大影响。; ZnO的等离子体蚀刻工艺使用多种等离子体化学方法进行：CH4 / H2-，C2H6 / H2-，Cl2-，IBr-，ICl-， BI3-和BBr3 / Ar。尽管侧壁不是完全垂直，但在基于甲烷的化学中，可以通过实际的蚀刻速率和非常光滑的表面实现高保真度的图形转移。所有等离子体化学物质的阈值能量均低至60 +/- 20 eV，这证实了在离子能量的整个范围内蚀刻都是由离子辅助机制驱动的;使用硼化物（CrB2和CrB2检查与p-CuCrO2的欧姆接触） W2B5），氮化物（TaN和ZrN）和高温金属（Ir）。这些材料被用作基于Ni / Au的接触中的扩散阻挡层，即Ni / Au / X / Ti / Au金属化方案，其中X是耐火材料。含Ir的触点在O2环境中在500--800°C的温度下退火60s后，获得的最小比接触电阻约为5x10 -4 O.cm2。与传统的Ni / Au触点相比，Ir扩散阻挡层的存在将触点的热稳定性提高了约200°C。与之形成鲜明对比的是，使用其他耐火材料导致热稳定性较差，接触电阻在400°C以上急剧增加。

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