氧化物薄膜晶体管及其有源材料的研究

发布时间：2018-06-19 11:26

本文选题：薄膜晶体管 + 氧化物半导体　；参考：《华南理工大学》2016年博士论文

【摘要】：薄膜晶体管(TFT)是液晶显示(LCD)和有源矩阵有机发光二极管(AMOLED)显示背板的核心部件;其中基于金属氧化物半导体有源层的TFT由于具有迁移率较高、成本低、工艺温度较低、均匀性好、对可见光透明以及与a-Si TFT产线兼容等优点而被认为是适合驱动AMOLED的TFT技术之一。随着平板显示向超高分辨率、超大尺寸以及柔性等方向发展,其对金属氧化物TFT(MO-TFT)的性能及工艺温度提出了更高的要求。因此,需要进一步提高MO-TFT的迁移率(20 cm2V-1s-1)和稳定性以满足超高分辨率、超大尺寸显示的驱动需求;另一方面,还需要进一步降低制备MO-TFT的工艺温度以匹配柔性衬底。本论文首先从器件着手,首次提出了一种利用溶剂对MO-TFT背沟道进行修饰从而提高器件性能的方法。由于氧化物表面通常对大气中的水、氧分子比较敏感,水、氧分子在氧化物背沟道的吸附/解吸附效应会严重影响MO-TFT的性能;利用溶剂对InGaZn O(IGZO)TFT背沟道进行修饰后,背沟道表面能显著降低,这极大地抑制了背沟道表面对水、氧的吸附/解吸附效应,有效减少了背沟道表面的氧杂质,器件表现出了更高的迁移率和更好的稳定性。在上述溶剂处理的基础上,为了进一步保护氧化物背沟道免受大气的影响,通常采取在其上加入无机钝化层以提高器件稳定性,但无机钝化层的制备通常会对有源层造成等离子伤害或氢掺杂,这严重恶化了器件性能。针对这一问题,基于前一部分工作的启发,我们利用有机分子在氧化物背沟道表面形成一层致密有序地自组装分子层,成功实现了高性能IGZO-TFT的制备,器件迁移率达26.6 cm2V-1s-1,阈值电压为0 V,磁滞回线0.06 V,在持续2.5 h的偏压(VG=10 V)下,阈值电压仅漂移0.14 V。该方法避免了钝化层制备对有源层的损伤;而且由于无需真空设备,也极大地降低了制造成本。此外,我们进一步研究了自组装分子所含烷基链长短对器件修饰效果的影响并探索了其相关机理,这为今后选择合适的自组装分子制备更高性能的MO-TFT提供了理论指导。前面的自组装分子层修饰氧化物的背沟道虽然可以大幅提高器件的性能,但是修饰后氧化物半导体层依然对酸敏感,在刻蚀源、漏电极时很容易被刻蚀液腐蚀,因此在实际应用中仍然需要增加刻蚀阻挡层(ESL)以保护沟道不被刻蚀。为实现无需ESL的背沟道刻蚀型TFT(BCE TFT),我们采用Au纳米粒子修饰氧化物半导体表面。在氧化物半导体薄膜上引入Au纳米粒子后,薄膜的抗刻蚀性显著增强,有效减少了图形化源、漏电极过程中刻蚀药液对有源层的损伤。利用该方法我们成功制备了BCE结构的IGZOTFT,偏光显微镜结果证明有源层并无明显损伤,器件也表现出了较好的电学性能。此种方法不受限于氧化物半导体材料的种类,无需额外的图形化步骤,为低成本制备MOTFT阵列开辟了一种新的途径。前面部分主要从器件角度提高MO-TFT的性能,虽然在稳定性方面取得了一定的效果,但在迁移率的进一步提高方面遇到了困难,需要设计和开发新的氧化物半导体材料才能突破迁移率的限制。因此,我们通过理论分析和计算验证,成功研制出了高迁移率Zr-In-O材料体系,并利用该材料作为有源层制备了TFT,器件迁移率高达38.8 cm2V-1s-1,电流开关比为3×108,亚阈陡度为0.37 V/decade,在VG=±20 V持续1 h阈值电压漂移分别为1.03 V和2.13 V,而且整个器件的最高工艺温度为150 oC,表明该材料在柔性TFT中有较大的应用潜力;为了进一步提高器件稳定性,我们采用了Zr InO/IGZO双层有源层结构,所制备的器件迁移率达36.2 cm2V-1s-1,电流开关比为3.5×109,亚阈陡度为0.09 V/decade,此外,器件表现了优异的偏压稳定性,在持续1 h的VG=±20 V的偏压下的阈值电压漂移分别只有0.2 V和0.97 V。由于前一部分Zr InO-TFT的最高工艺温度只有150 oC,我们考虑进一步将其制作在塑料衬底上以实现柔性Zr InO-TFT。但塑料衬底通常表面粗糙、水氧阻隔能力也较差,针对这一问题,我们采用无机-有机-无机(SiNx/Photoresist/SiNx)相结合制备了多层阻隔结构的缓冲层,成功在PEN衬底上实现了柔性ZrInO-TFT的制备,所制备的柔性TFT表现了良好的电学性能,其饱和迁移率达22.6 cm2V-1s-1,亚阈陡度为0.39 V/decade,电流开关比2.51×107,最小可弯曲的曲率半径为20 mm,展示了其在下一代柔性AMOLED显示的巨大应用前景。
[Abstract]:Thin film transistors (TFT) are the core components of the LCD display (LCD) and the active matrix organic light-emitting diode (AMOLED) display backplane. The TFT based on the metal oxide semiconductor active layer has high mobility, low cost, low process temperature, good uniformity, the transparency of visible light and compatibility with the a-Si TFT production line. As one of the TFT technologies suitable for driving AMOLED, with the development of flat panel display in the direction of ultra high resolution, super size and flexibility, the performance and process temperature of metal oxide TFT (MO-TFT) are higher. Therefore, the mobility of MO-TFT (20 cm2V-1s-1) and stability should be further improved to meet the high resolution. On the other hand, it is necessary to further reduce the process temperature of preparing MO-TFT to match the flexible substrate. In this paper, first of all, starting from the device, a method is proposed for the first time to improve the performance of the MO-TFT through the modification of the solvent to the channel of the trench. The adsorption / desorption effect of water and oxygen molecules on the oxide back channel seriously affects the performance of MO-TFT; the surface of the back channel can be significantly reduced after the modification of the InGaZn O (IGZO) TFT back channel with solvent, which greatly inhibits the adsorption / desorption of water and oxygen on the surface of the ditches and effectively reduces the surface of the trench channel. On the basis of the above solvent treatment, in order to further protect the oxide back channel from the atmosphere, the inorganic passivation layer is usually added to improve the stability of the device on the basis of the above solvent treatment, but the preparation of the inorganic passivation layer usually causes the plasma injury to the active layer. Damage or hydrogen doped, which seriously deteriorates the performance of the device. Based on this problem, based on the previous work, we use organic molecules to form a dense and orderly layer of self assembled molecular layer on the surface of the oxide back channel, successfully realizing the preparation of high performance IGZO-TFT, the mobility of the device is 26.6 cm2V-1s-1, the threshold voltage is 0 V, and the hysteresis is magnetic. The line 0.06 V, the threshold voltage drift only 0.14 V. under the continuous 2.5 h bias voltage (VG=10 V), the method avoids the damage to the active layer by the passivation layer; moreover, the manufacturing cost is greatly reduced because of no vacuum equipment. Furthermore, we further study the effect of the length of the alkyl chain in the self assembled subunit on the effect of the device modification. The related mechanism is explored, which provides theoretical guidance for the future selection of a suitable self assembled molecule for the preparation of higher performance MO-TFT. The back channel of the self assembled monolayer modified oxide can greatly improve the performance of the device, but the modified oxide semiconductor layer is sensitive to acid, and is easy to be used for the etching source and the leakage pole. The etching barrier (ESL) still needs to be added to protect the channel from etching. In order to realize the TFT (BCE TFT) without ESL, we use Au nanoparticles to modify the oxide semiconductor surface. The corrosion resistance of the film is remarkable after the introduction of Au nanoparticles on the oxide semiconductor thin film. It is enhanced effectively to reduce the graphical source and the damage to the active layer by the etching solution in the process of leakage. Using this method, we have successfully prepared the IGZOTFT of the BCE structure. The polarizing microscope results show that the active layer has no obvious damage, and the device also shows good electrical properties. This method is not limited to the type of oxide semiconductor material. There is no need for additional graphical steps to create a new way for low cost MOTFT arrays. The previous part mainly improves the performance of MO-TFT from the device angle. Although it has achieved a certain effect in stability, it is difficult to further improve the mobility, and new oxide semiconductor materials need to be designed and developed. In order to break through the limitation of mobility, we have successfully developed a high mobility Zr-In-O material system by theoretical analysis and calculation, and using this material as an active layer to prepare TFT, the mobility of the device is up to 38.8 cm2V-1s-1, the current switch ratio is 3 x 108, the subthreshold steepness is 0.37 V/decade, and the 1 h threshold voltage of VG= + 20 V is sustained. The drift is 1.03 V and 2.13 V respectively, and the maximum process temperature of the whole device is 150 oC, which indicates that the material has great potential application in the flexible TFT. In order to further improve the stability of the device, we adopt the Zr InO/IGZO double layer active layer structure, the mobility of the device is 36.2 cm2V-1s-1, the current switch ratio is 3.5 x 109, subthreshold The steepness is 0.09 V/decade, in addition, the device shows excellent bias stability. The threshold voltage drift of the threshold voltage is only 0.2 V and 0.97 V. under the VG= + 20 V bias voltage of 1 h. The maximum process temperature of the previous part of Zr InO-TFT is only 150 oC. We consider making it more flexible on the plastic substrate to realize the flexible Zr InO-TFT. but plastic. The material substrate is usually rough and water oxygen barrier ability is poor. In view of this problem, we use inorganic organic inorganic (SiNx/Photoresist/SiNx) to prepare the buffer layer of multilayer barrier structure. The flexible ZrInO-TFT is successfully prepared on the PEN substrate. The flexible TFT shows good electrical performance, and its saturated migration is saturated. The shift rate is 22.6 cm2V-1s-1, the subthreshold steepness is 0.39 V/decade, the current switch ratio is 2.51 x 107, the minimum curvature radius is 20 mm, which shows its great application prospect in the next generation of flexible AMOLED display.
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN321.5

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