基于AM-OLED的a-Si：H TFT的设计与工艺研究

【作者】 曹伟；

【导师】 林祖伦；

【作者基本信息】 电子科技大学 ， 光学工程， 2009， 硕士

【摘要】 有源矩阵驱动显示技术已经成为当前平板显示技术的主流。非晶硅薄膜晶体管(a-Si:H TFT)作为一种成熟的电子器件,因其大面积制造成本低廉、工艺重复性良好、开关速度适当,非常适合于有源矩阵显示器件。此外,a-Si:H TFT较低的制备温度使其具有可制作在柔性基底的优点。因此,采用具有液晶显示产业化基础的a-Si:H TFT来驱动OLED无疑具有重大的意义。本文以研制性能优良AM-OLED用a-Si:H TFT为目的,探索了a-Si:H TFT的制备工艺,并研究了a-Si:H TFT对AM-OLED稳定性的影响。(1)a-Si:H TFT组成膜的制备。采用PECVD方法,通过改变工艺参数,分别在不同衬底上沉积一系列a-SiNx:H、a-Si:H及n~+Si:H薄膜样品。使用椭圆偏振仪、超高电阻微电流计等测试仪器对样品薄膜进行测试,摸索出沉积各层薄膜的较佳的工艺参数。(2)a-Si:H TFT的结构设计。结合OLED的需求及a-SiNx:H、a-Si:H及n~+Si:H薄膜的光电特性,设计TFT结构为背沟道刻蚀型,结构参数如下:a-SiNx:H厚度为300nm、a-Si:H的厚度为200nm、n~+Si:H的厚度为50nm,栅极与源漏极采用的低电阻率Al电极厚度为200nm。此外,根据TFT结构设计和整体布局,论文设计了三块掩膜板,以获得所需的a-Si:H TFT结构阵列。(3)a-Si:H TFT的制备。采用传统的光刻和刻蚀工艺,经三次套刻获得整体a-Si:H TFT阵列,其中,SiNx、a-Si:H、n~+a-Si膜的干法刻蚀选用SF6气体等离子刻蚀,Al膜的湿法刻蚀选用盐酸、磷酸和水的配比刻蚀液。(4)a-Si:H TFT性能测试。通过测试TFT漏极电流与栅极电压,获得所制备a-Si:H TFT的转移曲线;测量了a-Si:H TFT的开关比,并对影响a-Si:H TFT性能的主要因素进行了分析。(5)研究a-Si:H TFT特性对AM-OLED稳定性的影响。主要分析了电流控制电流镜像像素电路的稳定性,并提出改进方案以补偿a-Si:H TFT阈值漂移特性对驱动电流稳定性的影响。更多还原

【Abstract】 Recent advances in organic light emitting diode (OLED) device efficiencies are making the amorphous silicon (a-Si) backplane a viable solution for a large range of display sizes. The a-Si:H thin-film transistor (TFT) technology is mature and well suited to produce active matrix display devices in view of its low fabrication costs over large areas, good process uniformity and adequate switching speed, the option of a low-temperature process that allows the fabrication of TFTs and circuits on mechanically flexible substrates. So it makes high sense to introduce a-Si:H TFT used widely in LCD industrials to drive OLED undoubtedly. In this paper, with the purpose of preparing excellent a-Si:H TFT for the use of AM-OLED, the manufacture technology of a-Si:H TFT was obtained, meanwhile, the influence of a-Si:H TFT to the stability of AM-OLED was researched.(1)A series of a-SiNx:H, a-Si:H, n~+Si:H thin films were prepared on glass substrate by varying deposition parameters in the experiments. The properties of the samples under different conditions were tested by a series of testing apparatuses, including ellipsometry, super-high resistance micro-amperemeter. Finally, The perferable technology parameters in the deposition of each film layer were obtained.(2)With the demand of OLED, and considering the optoelectronic characteristics of a-SiNx:H, a-Si:H and n~+Si:H film materials and practical technology level, the back channel etching TFT widely used in AM-OLED was introduced, and the structural parameters was as follows: the thickness of a-SiNx:H, a-Si:H and n~+Si:H was respectively 300nm, 200nm, 50nm, and the thickness of Al electrode with low resistance ratio used as grid, source and drain electrode was 200nm.(3)According to the structural design and the whole layout of TFT, three masks have been used in this paper. These masks were drawn by computer design drawing software, and made by photolithography technology in chromium plate. A large number of experiments were made to find out the optimal technology parameters in the etching technology of each film. Finally, the whole a-Si:H TFT array was obtained by three nesting. In the experiments, SF6 ion etching technology was used in the dry etching of a-SiNx:H, a-Si:H and n~+Si:H film, and the mixed liquid of HCl, H3PO4, HNO3 and H2O was used as etching solution in the wet etching of Al film.(4)The performences of a-Si TFT were tested, and the factors influencing the performences were analyzed. Finally, the manufacture technology was concluded and improved to enhance the performences of a-Si TFT.(5)The influence of the performences on the stability of AM-OLED was researched, especially for the stability of self-controlling current mirror-based pixel circuits. The improved method was introduced to compensate the influence of the threshold shifting characteristics on the stability of driving current.更多还原