溶液法制备超薄高k介电层和InMZnO体系透明薄膜晶体管的关键问题研究

Due to their high mobility, room temperature fabrication, large area production and low cost, the amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) had received extensive attention from academia and industry. However, the AOS TFTs reported in the literature usually have difficulties in their electrical stabilities, and the high operation voltages are needed to obtain the large drain current. The current object is to fabricate the AOS TFTs with high stabilities and low operation voltages. The main object in this project is to fabricate the AOS InMZnO-TFTs based on ultra-thin high-k dielectrics by using sol-gel technique and sputtering technique. This project includes 3 main parts: 1) to fabricate the ultra-thin high-k dielectrics on flexible substrates at low temperature by using sol-gel technique and "UV-photo annealing" process. The ultra-thin dielectric thin film with large dielectric constant and low leakage current would certainly make the AOS TFT high performance; 2) low-temperature fabrication of the InMZnO channel layer: We will perform the experiments to improve the electrical properties of the channel layer by changing the sorts of M element, the chemical ratios of M in InMZnO channel layer, by optimizing the experimental conditions and the post annealing processes. 3) To fabricate the high performance AOS TFTs on flexible substrates with low operation voltage and high stability. Such TFTs will have important scientific interests and wide applications in flat panel displays.

非晶氧化物半导体(AOS)薄膜晶体管(TFT)具有迁移率高、室温制备、适合大面积生产、成本低等优点，引起了学术界和工业界浓厚的兴趣。然而目前报道的TFT通常稳定性较差并且需要大的电压获得大的输出电流。低温制备高稳定并且低操作电压的TFT成为最新的研究热点。本项目在柔性衬底上利用溶胶凝胶和物理溅射技术低温制备基于超薄高k介电层的InMZnO体系AOS TFT。本项目包括三部分：1)利用溶胶凝胶技术和"紫外光退火"工艺在柔性衬底上制备超薄高k介电薄膜，降低薄膜的制备温度。介电薄膜的高k值和低漏电流可以保证TFT的优异性能；2)利用溅射技术低温制备InMZnO沟道层，通过改变M元素种类和化学配比，改变实验条件和后退火工艺等提高沟道层的电学性能和稳定性。3)在柔性衬底上制备性能优异、可低电压工作、高稳定性的AOS TFT。该TFT在未来的平板显示领域具有重要的科学价值和广阔的应用前景。

金属氧化物薄膜晶体管（TFTs）具有载流子迁移率高，可见光透过率高，可以低温制备，适合大面积生产，成本低等优点，引起了学术界和工业界浓厚的兴趣。本项目利用溶胶凝胶(sol-gel)技术低温制备基于超薄高k介电层的InMZnO体系的TFTs。主要研究内容包括：1）利用sol-gel技术和“紫外光退火”工艺相结合，制备超薄介电薄膜；2）探究工艺条件对半导体沟道层的影响，提高沟道层的电学性能和稳定性；3）通过对超薄介电层和沟道层的集成，实现全溶液法TFT器件；4）改善TFT器件的稳定性，实现柔性、透明的TFTs器件。在本项目的资助下，项目组在Advanced Materials, Advanced Functional Materials, Advanced Electronic Materials, ACS AMI, JMCC等国际著名学术期刊上发表有影响力的论文36篇，其中中科院大类一区文章15篇，大类二区文章16篇，获批发明专利7项。本课题组采用sol-gel技术成功制备了多种超薄高k介电薄膜(AlOx，YOx，HfOx，LiOx，MgO，Yb2O3，SrOx等)，该系列介电薄膜的厚度只有7-20 nm，是世界上已报道最薄的氧化物介电薄膜，被审稿人评价为具有世界性开创意义。本课题组首次将“水性溶胶”技术应用于制备高k YOx介电层和InZnO沟道层，构建了全水溶液场效应晶体管，该晶体管具有出色的电学性能，迁移率达到25 cm2/V s，电流开关比达到106，操作电压为1.5 V。这种绿色环保、低成本的“水性溶胶”工艺显著降低了器件的制备温度，是替代传统溶液法的理想方法。针对p型TFTs，本课题组提出采用燃烧合成方法，在低至150℃下成功制备Cu掺杂的NiO，并在玻璃衬底上成功构建场效应晶体管，得到空穴迁移率为1.53 cm2/V s，开关比为104。同时，静电纺丝技术是制备纳米纤维最有效的方法之一，具有工艺简单、成本低、能够大面积制备，且兼容多种衬底等优势，本课题组利用静电纺丝工艺制备了InHfO纳米纤维/高k ZrOx场效应晶体管，得到具有良好性能的晶体管，包括迁移率25 cm2/Vs，开关比108，SS值90 mV/dec, 操作电压3 V。以上TFTs在未来的平板显示领域具有重要的科学价值和广阔的应用前景。