锂氮掺杂氧化锌薄膜晶体管的制备与性能

发布时间：2018-03-25 01:03

  本文选题：ZnO　切入点：薄膜晶体管　出处：《北京交通大学》2016年博士论文

【摘要】：ZnO基TFT因其在平板显示和透明电路领域的广阔应用前景而备受国内外的关注。由于ZnO中存在Zn填隙、O空位等本征缺陷,致使常规制备的ZnO薄膜中载流子浓度会较大,使得制备的未掺杂的ZnO-TFT的关态电流较大,开关比偏小；而现已报道的掺杂的ZnO基TFT性能又不够理想。提高ZnO基TFT性能的一个关键是有效地调控有源层的载流子浓度。Li和N分别作为Zn和O的合适的替位者(Lizn和No),可调节ZnO中的载流子浓度,通过合理掺杂Li和N,有望提高ZnO-TFT的性能。基于以上考虑,本论文主要制备了Li、N掺杂的ZnO基TFTs,并通过优化有源层沉积条件,得到了性能优良的ZnO基TFT。主要研究内容如下：(1)用磁控溅射在SiO2/p-Si衬底上研制出了ZnO:Li-TFT,研究了退火温度、有源层厚度、沟道宽长比对其性能的影响。实验结果表明,有源层厚度为30 nm,退火温度为800℃时器件性能最佳,其迁移率为7.6 cm2/V s,开关比为2.3×107。与Al、Mg、Ga等掺杂的ZnO-TFTs相比,其性能有所改善。(2)用磁控溅射制备了ZnO:N-TFT,研究了退火温度、有源层厚度、沟道宽长比对其性能的影响,并研究了该器件的稳定性。实验结果表明,有源层厚度为30 nm,退火温度为800℃时器件性能最佳,其迁移率为22.1 cm2/Vs,开关比为1.1×108,开态电流为9.4×10-3A。相比已报道的A1、Mg、Ga等掺杂的ZnO-TFTs,其性能有显著提高；相比本征ZnO-TFTs,其开关比也有很大改善。结果表明,该器件在空气中放置120天仍保持较高迁移率μSAT=19.3·cm2/Vs,有较好稳定性。(3)用磁控溅射制备了底栅极结构的ZnO:(Li,N)-TFT。研究了退火温度、有源层厚度、沟道宽长比对其性能的影响,并探究了该器件的稳定性。实验结果表明,30 nm厚的有源层800℃退火的器件性能最佳,其迁移率高达33.6 cm2/Vs,开关比高达1.1×108,开态电流为8.2×10-3A;相比已报道的A1、Mg、Ga等掺杂的ZnO-TFTs和本征ZnO-TFTs,其性能均有显著提高,表现出Li-N共掺杂的优越性。该器件在空气中放置180天后,迁移率稍微降至31.2cm2/Vs,表明了器件良好的稳定性。(4)用磁控溅射制备了未退火的ZnO:(Li,N)-TFT,研究了有源层厚度、紫外臭氧处理、氩氧气流比以及A1203缓冲层对器件性能的影响,并探讨了器件稳定性。实验结果表明,有源层厚度为20 nm时器件性能最佳,其迁移率为13.5 cm2/Vs,开关比为8.1×107,阈值电压为7.6V。该器件在空气中放置60天后,迁移率增大到15.7 cm2/Vs;放置120天降低到10.9 cm2/Vs,表现出较好的稳定性。研究表明,增加氧气流量和A1203缓冲层不利于ZnO:(Li,N)-TFT性能的提高,而有源层经UV-Ozone处理后的器件性能有所提高,其迁移率为15.3 cm2/V s,开关比为1.2×108,阈值电压为9.9V。
[Abstract]:ZnO based TFT has attracted much attention because of its wide application prospect in flat panel display and transparent circuits. Due to the intrinsic defects such as Zn gap and O vacancy in ZnO, the carrier concentration in conventional ZnO films will be larger. The off-state current of the prepared undoped ZnO-TFT is larger and the switching ratio is smaller. One of the key points to improve the performance of ZnO based TFT is to regulate the carrier concentration of active layer. Li and N are suitable substitutes for Zn and O, respectively, which can be adjusted. Carrier concentration in ZnO, It is expected to improve the performance of ZnO-TFT by doping Li and N reasonably. Based on the above considerations, we have prepared Li-N-doped ZnO based TFTs and optimized the deposition conditions of active layers. The main research contents are as follows: (1) ZnO: Li-TFTs have been fabricated on SiO2/p-Si substrate by magnetron sputtering. The effects of annealing temperature, thickness of active layer and ratio of channel width to length on the properties of TFTs have been studied. When the thickness of active layer is 30 nm, the annealing temperature is 800 鈩，

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