Preparation method for thin film transistor, preparation method for array substrate, array substrate, and display apparatus

A method for manufacturing a thin-film transistor (TFT), comprising:

• forming a pattern of a semiconductor layer on a base substrate;
• forming an interlayer dielectric layer on the pattern of the semiconductor layer;
• forming a first photoresist pattern on the interlayer dielectric layer, the first photoresist pattern including first-thickness photoresist and second-thickness photoresist;
• the first-thickness photoresist corresponding to an area, at which a channel region is to be formed, in the pattern of the semiconductor layer;
• the second-thickness photoresist corresponding to areas, at which a source lightly doped region and a drain lightly doped region are to be formed, in the pattern of the semiconductor layer;
• the first-thickness photoresist has a thickness greater than that of the second-thickness photoresist;
• performing heavily doped ion implantation on the pattern of the semiconductor layer by taking the first photoresist pattern as a barrier mask, and forming patterns of a source heavily doped region and a drain heavily doped region;
• performing ashing treatment on the first photoresist pattern, so as to remove the second-thickness photoresist and reduce the thickness of the first-thickness photoresist, and form a second photoresist pattern;
• performing lightly doped ion implantation on the pattern of the semiconductor layer by taking the second photoresist pattern as a barrier mask, and forming patterns of the channel region, the source lightly doped region and the drain lightly doped region;
• and
• removing the second photoresist pattern.