Am-oled-based A-si: H Tft Design And Technology Research

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.