多元金属氧化物n型半导体薄膜制备与性能研究

发布时间：2018-03-31 06:03

本文选题：氧化铟镓锌　切入点：霍尔迁移率　出处：《清华大学》2016年博士论文

【摘要】：非晶氧化铟镓锌(InGa ZnO_4,IGZO)作为一种新型的薄膜晶体管(thin film transistor,TFT)有源层材料,相比于传统氢化非晶硅(a-Si:H),具有迁移率高、透过率高、均匀性好以及制备温度低等诸多优势,被认为是下一代平板显示技术关键材料。本文采用磁控溅射法制备非晶IGZO薄膜,系统深入研究工艺参数对IGZO薄膜电学性能的影响,并分析工艺参数对IGZO薄膜载流子浓度与Hall迁移率的作用机制。针对IGZO薄膜载流子输运特性进行重点研究,揭示影响迁移率大小的内在本质,同时提出对渗流传导模型的修正。在此基础上,首次提出用Nb元素替代Ga元素,设计并制备INZO薄膜,进一步提高Hall迁移率,降低与TFT器件稳定性相关的深能级隙态缺陷。本文主要研究内容和成果如下:系统深入地研究了溅射电流、氧气流量、基底温度以及退火温度对IGZO薄膜载流子浓度和Hall迁移率的影响,揭示其作用机制。载流子浓度主要取决于作为施主型缺陷的氧空位的数量。Hall迁移率受载流子浓度与微观结构两方面因素共同作用。载流子浓度、结构无序程度的变化,均会改变势垒起伏对载流子的散射作用,从而影响薄膜Hall迁移率。在优化工艺条件下,制备得到了高质量的IGZO薄膜,在符合TFT器件制备要求的载流子浓度范围内(6.01×10~(16) cm~(-3)),最高Hall迁移率达19.1 cm~2·V~(-1)·s~(-1),为非晶硅的近20倍;针对IGZO薄膜载流子输运特性进行系统研究,揭示载流子输运机制为渗流传导。引入势垒宽度因子对渗流传导数学模型进行修正,提出本征迁移率可表示为能量高于势垒起伏的电子所具有的迁移率与势垒宽度因子的乘积。IGZO薄膜Hall迁移率变化的内在本质为势阱宽度的改变以及平均势垒高度的改变。通过光致发光技术对IGZO薄膜深能级隙态缺陷进行表征,分析并揭示了各发光峰的激发机制与发射机制。结果表明,529 nm与698 nm处的发光与氧空位深能级缺陷相关,发光源于电子从导带或导带带尾态至氧空位缺陷的辐射跃迁。提出用Nb元素替代Ga元素设计并制备INZO薄膜,系统研究氧气流量与基底温度对INZO载流子浓度与Hall迁移率的影响并分析作用机制。研究表明,INZO薄膜Hall迁移率较高源于势阱宽度较宽以及势垒高度较小,深能级隙态缺陷较少则源于Nb对氧空位的抑制。在优化工艺条件下制备得到了高质量的INZO薄膜。在载流子浓度为10~(19)~10~(20) cm~(-3)范围内,INZO最高Hall迁移率为45.0 cm~2·V~(-1)·s~(-1)。
[Abstract]:As a new type of thin film transistor film transistor-TFT-based active layer material, InGaO4ZO has many advantages, such as high mobility, high transmittance, good uniformity and low preparation temperature, compared with conventional hydrogenated amorphous silicon.It is considered to be the key material of the next generation flat panel display technology.Amorphous IGZO thin films were prepared by magnetron sputtering. The effects of process parameters on the electrical properties of IGZO thin films were studied systematically. The mechanism of the effects of process parameters on the carrier concentration and Hall mobility of IGZO thin films was analyzed.The carrier transport characteristics of IGZO thin films are studied in order to reveal the intrinsic nature of the mobility and the modification of the percolation conduction model is proposed.On this basis, the NB element is used to replace Ga element for the first time to design and prepare INZO thin films, which can further improve the Hall mobility and reduce the deep level gap state defects related to the stability of TFT devices.The main contents and achievements are as follows: the effects of sputtering current, oxygen flow rate, substrate temperature and annealing temperature on the carrier concentration and Hall mobility of IGZO thin films have been investigated.The carrier concentration mainly depends on the number of oxygen vacancies as donor defects. Hall mobility is affected by both carrier concentration and microstructure.The variation of carrier concentration and structure disorder will change the scattering effect of barrier fluctuations on the carriers and thus affect the Hall mobility of the films.A high quality IGZO thin film was prepared under the optimized conditions. In the carrier concentration range of 6.01 脳 10 ~ (-1) ~ (16) cm ~ (-1) ~ (-1) TFT, the highest Hall migration rate was 19.1 cm~2 ~ (-1) ~ (-1) Si ~ (-1), which was about 20 times of that of amorphous silicon.The characteristics of carrier transport in IGZO thin films are systematically studied, and it is revealed that the carrier transport mechanism is percolation conduction.Introducing the barrier width factor to modify the mathematical model of seepage conduction,It is proposed that the intrinsic mobility can be expressed as the product of energy higher than the barrier fluctuation and the product of barrier width factor. The intrinsic essence of the Hall mobility change of IGZO thin films is the change of the potential well width and the average barrier height.The deep level gap state defects of IGZO thin films were characterized by photoluminescence technique. The excitation and emission mechanisms of each luminescence peak were analyzed and revealed.The results show that the luminescence at 529 nm and 698 nm is related to the deep level defect of oxygen vacancy, and the luminescence results from the radiative transition of electron from the tail state of conduction band or conduction band to the defect of oxygen vacancy.INZO thin films were designed and prepared by NB instead of Ga. The effects of oxygen flow rate and substrate temperature on INZO carrier concentration and Hall mobility were systematically studied and the mechanism of action was analyzed.The results show that the higher Hall mobility of Inzo thin films is due to the wide potential well width and the lower barrier height, and the lower defects in deep level gap states are due to the inhibition of oxygen vacancies by NB.High quality INZO thin films were prepared under optimized conditions.The highest Hall mobility is 45.0 cm~2 / v ~ (-1) ~ (-1) in the carrier concentration range of 10 ~ 19 ~ 10 ~ 10 ~ 10 ~ (-1) cm ~ (-1) ~ (-1) ~ (-1) ~ (-1) ~ (-1) ~ (-1) 路cm ~ (-1) ~ (-1) ~ (-1)).
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN304.055;TN321.5

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