1. Field of the Invention
The present invention relates to the field of flat panel display technology, and in particular to a method for manufacturing a thin-film transistor and a thin-film transistor manufactured with the method.
2. The Related Arts
Liquid crystal displays (LCDs) have numerous advantages, such as thin device body, less power consumption, and being free of radiation, and is thus widely used. Most of the liquid crystal displays available in the market are backlighting liquid crystal displays, which comprise a liquid crystal display panel and a backlight module. The operation principle of the liquid crystal display panel is that liquid crystal molecules are arranged between two parallel glass substrates and electricity is selectively applied to the glass substrates to control change of the orientation of the liquid crystal molecules in order to refract out the light from a backlight module for formation of an image.
A liquid crystal display panel is generally composed of a color filter (CF) substrate, a thin-film transistor (TFT) substrate, liquid crystal (LC) interposed between the CF substrate and the TFT substrate, and a sealant. A general manufacturing process comprises a front stage of array process (including thin film, yellow light, etching, and film stripping), an intermediate stage of cell process (including bonding TFT substrate and the CF substrate), and a rear stage of assembling process (including mounting drive ICs and printed circuit board). The front stage of array process generally makes the TFT substrate for controlling the movement of liquid crystal molecules. The intermediate stage of cell process generally introduces liquid crystal between the TFT substrate and the CF substrate. The rear stage of assembling process generally mounts the drive ICs and combining the printed circuit board to effect driving the liquid crystal molecules to rotate for displaying images.
The TFT substrate generally comprises a glass substrate and TFTs formed on the glass substrate. The thin-film transistors are generally of three structures, which are a coplanar structure, an island-stop structure, and a BCE (back channel etch) structure. The currently available oxide thin-film transistors primarily belong to the coplanar structure and the island-stop structure. This is because the BCE structure may cause damage to the oxide semiconductor layers in the manufacturing process and thus affect the electrical property thereof.
Referring to FIG. 1, a schematic view is given to illustrate the structure of a BCE structure thin-film transistor that is formed on a glass substrate 100 through a five-masking-operation manufacturing process and comprises a gate terminal 101 formed on the glass substrate 100, a gate insulation layer 103, a oxide semiconductor layer 105 formed on the gate insulation layer 103, and a source/drain terminal 107 formed on the oxide semiconductor layer 105. The oxide semiconductor layer 105 comprises at least one of zinc oxide (ZnOx), tin oxide (SnOx), indium oxide (InOx), and gallium oxide (GaOx) and indium gallium zinc oxide (IGXO) is commonly used. The source/drain terminal 107 is generally composed of an aluminum (Al) layer and a molybdenum (Mo) layer sequentially formed on the oxide semiconductor layer 105 through sputtering, followed by coating of photoresist material, exposure, development, etching, and removal of the photoresist material. An etching operation is applied in processing the aluminum layer and the etchant solution used is generally a mixed acid of phosphoric acid (H3PO4) and nitric acid (HNO3). However, the mixed acid of phosphoric acid and nitric acid may also react with the oxide semiconductor layer 105, making the oxide semiconductor layer 105 etched away and thus affecting the electrical property of the thin-film transistor and deteriorating the quality of the thin-film transistor.