【作者】 罗东向；

【导师】 彭俊彪；

【作者基本信息】 华南理工大学 ， 材料物理与化学， 2014， 博士

【摘要】 高性能薄膜晶体管（TFT）背板技术是以有源驱动有机发光二极管（AMOLED）为代表的平板显示（FPD）产业的共性技术和核心技术，也是FPD产业提高产品质量、降低生产成本的重要环节。随着大尺寸、高分辨、3D显示技术的快速发展，其对TFT背板的要求越来越高。然而，传统的非晶硅TFT迁移率较低，无法实现高分辨率显示；多晶硅TFT迁移率高，但其存在生产工艺复杂、设备投资高、均匀性差、良品率低等难以克服的问题，实现大面积显示成本较高；金属氧化物TFT（MOTFT）近年来备受业界关注，其迁移率较高、工艺简单、成本低，容易实现大面积制备，并且与非晶硅TFT生产线相兼容，成为目前业界的新焦点。因此，开展对新兴的、在FPD产业上较有应用前景的MOTFT的研究工作具有现实的意义。本论文研究了栅极绝缘材料及其制备工艺。由于栅极绝缘层决定着薄膜晶体管的击穿电压、泄漏电流等重要工作参数，因此获得高介电常数、高质量的栅极绝缘层显得极为重要。基于此，我们开发出了阳极氧化Al2O3薄膜制备新工艺，在氧化制备过程中使用数控系统对氧化信号进行编程，研制的Al2O3薄膜具有高介电常数（~10）、高击穿电场（~6MV/cm）、低泄漏电流（<10-8A/cm2）的优点。这种制备方法即避免使用贵重的真空设备，节约了成本，又提高了栅介质薄膜的大面积均一性，十分适合大尺寸AMOLED显示屏的制作。同时，为了解决栅极Al薄膜在高温下容易产生表面小丘的问题，本论文又研制了基于Al-Nd和Al-Ce合金栅极的阳极氧化Al2O3，以提高Al/Al2O3体系的热稳定性，得到的Nd:Al2O3和Ce:Al2O3绝缘层在高温下表面平整、膜层致密，完全能够抑制小丘的形成。研究表明，Nd或Ce会扩散进入到半导体内，对MOTFT的器件性能产生重要影响。其中，Ce元素产生电荷陷阱缺陷，严重恶化器件的电学性能；Nd元素则能抑制氧空位和杂乱的自由电子，改善器件的电学性能。因此，Nd与金属氧化物半导体具有较好的兼容性，基于阳极氧化Nd:Al2O3绝缘层的MOTFT在FPD产业上有较大的应用潜力。由于Al合金栅极的电阻率过高，增加了显示屏的信号延迟，其无法实现更大尺寸和要求高响应速度的视频显示。因此，我们发明了一种埋入式Al栅极结构，仅使用加厚的纯Al栅极和辅助的埋入材料（JSR-NN901），工艺简单，不增加光刻步骤，即能满足电阻率的要求，解决了信号延迟的问题，又能提高Al薄膜的热稳定性，抑制了小丘的产生。基于埋入式Al栅极的MOTFT展示出了低工作电压、高迁移率、高电学稳定性、高可靠性的特点。这种简单而有效的工艺技术很有希望应用在大尺寸、高响应速度的新型显示技术中。为了获得低成本、高分辨率的显示屏，在制备MOTFT源、漏电极的工艺过程中需要采用背沟道刻蚀结构。但是，由于金属氧化物半导体基本上对各种酸性刻蚀液和干法刻蚀等离子体都很敏感，很容易被腐蚀或受到损伤，因此刻蚀源、漏电极十分困难。经过研究，本论文提出了两种工艺方法：一种是采用弱酸性的H2O2基刻蚀液图形化源、漏电极，并利用低能量的SF6plasma对背沟道进行修饰；第二种是采用C纳米薄膜作为背沟道的缓冲层，此方法不受刻蚀液限制，具有普适性。上述两种方法均不需要特殊的设备，且不增加光刻掩膜版次数，制备出的MOTFT背沟道无损伤，表现出了优越的器件性能和良好的电学稳定性。其对设备无要求、低成本、宽工艺窗口的特点使得上述背沟道无损伤的MOTFT制造技术有很大应用潜力替代现有技术。结合上述方法，本论文进一步延伸其应用，利用MoO3作为背沟道的电荷存储层，研制了新型的非易失性存储器件，所制备的存储器件具有电荷保留时间长、重复性高、读写时间短、密度高的特点。其可制作全透明存储器的潜力，使真正的“全透明”显示屏成为可能。基于前面对MOTFT新结构、新制备工艺的研究开发，本论文改进了MOTFT驱动背板的工艺实现路线，使光刻掩膜版次数从7次减少到5次，并在此基础上进行工艺版图设计，成功实现了AMOLED显示屏的制作。最后，结合使用拥有自主知识产权的新型半导体材料体系，开发出了2-7英寸等多款MOTFT驱动背板，并成功驱动包括单色、彩色、透明、柔性等显示屏，实现了基于MOTFT的AMOLED图像和视频显示。因此，MOTFT在AMOLED等新型显示技术上的应用将会有很大的突破。更多还原

【Abstract】 High-performance thin-film transistor (TFT) backplane technology is the basictechnology and center element in flat panel display (FPD) industry, such as active matrixorganic light-emitting diode (AMOLED). It is also the common key technology in otherFPDs industry to improve the quality of the display and reduce the production costs. With thelarge-size, high-resolution,3D displsy technologies rapid development, those increasinglyhigh requirements for TFT backplane. However, the traditional a-Si TFT has low carriermobility, so it is hard to achieve high-resolution display; and polysilicon (p-Si) TFT hashigher mobility, be widely used in high-resolution AMOLED, but the manufacturing processis complexity, the production costs is high, the uniformity is poor, and the yield is low, whichrestrict its development in the large-size FPDs. In recent years, the research on MOTFT hasgained huge progress. MOTFT is famous for its high mobility, good uniformity and goodstability. It is one of the most competitive TFTs in AMOLED. Therefore, it is very impormantto research the new AMOLED technologies based on MOTFT.This work firstly focuses on gate insulator. As the gate insulator layer determines thebreakdown voltage, the leakage currnet, and other important device operating parameters,thus obtaining a high dielectric constant, high-quality gate insulator layer is extremelyimportant. In order to meet the low cost, suitable for the preparation of large arearequirements in industry, we use the high dielectric constant Al2O3as the insulator anddeveloping a new anodizing process that avoids the use of expensive vacuum equipment.Anodized Al2O3prepared by using the improved anodic oxidation process exhibites a highdielectric constant (~10), a high breakdown electric field (~6MV/cm), and a low leakagecurret (<10-8A/cm2), which is very suitable for the production of large-size AMOLEDdisplays.However, the device has poor reliability because the Al hillocks damage the Al2O3insulator layer, due to the poor thermal stability of pure Al film under heat treatment. Thus,we propose Al alloy, such as Nd or Ce, as a gate to improve the thermal stability of Al/Al2O3structure, and achieved good results under high temperature. Experiments shows that Nd andCe ions are existence in the oxide film obtained by anodizing Al alloy, and they would diffuse into IZO film. The Ce ion could act as an electron trap, so the IZO-TFTs with Al-Ce gatewould experience seriously degradation. On the other hand, Nd ion is stable and would notproduce electron traps. Moreover, the existence of Nd would suppress undesirable freeelectron formation in the channel. Therefore, rare earth element Nd has a good compatibilitywith IZO, and anodizing Nd:Al2O3dielectric layer can actually be used in MOTFT devices,which has a great application potential in AMOLED displays.With the development of large-size display, Al alloy gate began to show the drawbacksof high resistivity, hence increase the signal delay of the displays. Therefore, we proposeusing buried thick Al gate structure to meet the low resistivity and solve the problem of signaldelay, which use only the thicking of pure Al and an auxiliary material named JSR-NN901.Pure Al film has mature preparation process and low cost, and thick Al further enhance thethermal stability of the pure Al can effectively suppress the generation of hillocks. MOTFTsprepared by this method exhibit high mobility, high electrical stability, high reliability.Therefore, MOTFTs with buried thick Al gate structure is a simple and effective technique,which has a great opportunity in the large-size TFT backplane manufacturing process.In order to obtain low cost and high resolution displays, the back-channel-etch (BCE)structure need to be used in the preparation of source/drain (S/D) electrodes. However, it isdifficulty to pattern them because metal oxide semiconductor materials are very susceptibleto most commonly used etchants and plasma treatment employed in wet-etch and dry-etchprocesses, respectively. Thus, we propose two methods to improve the performance for TFTbased on BCE structure: one is using H2O2-based etchant in combination with SF6plasmatreatment; the other is using an amorphous carbon (C) nanofilm inserted into the interfacebetween IZO and S/D electrodes as a barrier layer. The second method is not restricted byetchants, which has the universality characteristics. Experimental results show that thesemethods are simple and effective to fabricate high performance, high reliability MOTFT andwill be more and more attention in the production of high resolution MOTFT backplane.Then, we are inspired by the above results that the MoO3-residue layer may be associatedwith the operation mechanisms of some nonvolatile memories, thus providing the opportunityto extend the applications of metal oxide semiconductors to transparent memory devices thatcan be integrated with other transparent circuit elements. This also makes it possible to design freedom for system-on-panel applications for real, fully transparent displays.Based on the research on the MOTFT, we improve the traditional manufacture processof the MOTFT backplane, and develop a new type of process technology. Thus the number ofphotolithographic mask decreases from7times to5times. Then, we successfully achieved theproduction of AMOLED display. Finally, we develop a variety of2to7inch AMOLED basedon MOTFT backplane by using our new semiconductor material system, which hasindependent intellectual property rights, and realize images and video including monochrome,full color, transparent, and flexible display. Thus, we can see the future of the MOTFT.更多还原