Generally, a-si TFT is mainly composed of glass substrate, gate electrode, gate insulation layer, semiconductor active layer a-si, ohmic contact layer n+ a-si, source leakage electrode and protective film, among which the gate insulation layer and protective film generally use SiN.
The structure of a-si TFT can be divided into four typical structures: the planar structure with the source, leakage and gate electrode located on the same side of a-si in the active semiconductor layer.The cross-structure of source, leakage, electrode and grid electrode is located on both sides of a-si layer, in which the grid electrode is on the upper side of a-si layer, the source and leakage electrode on the lower side of a-si layer is called positive grid cross-structure or top grid structure, the grid electrode is on the lower side of a-si layer, and the source and leakage electrode on the upper side of a-si layer is called inverted grid cross-structure or bottom grid structure.
From the point of view of the manufacturing process, the SiN, a-si and n+ a-si layers (or two of them) of the staggered structure can accumulate continuously, which is suitable for flow operation and can reduce cross contamination.Now, the staggered structure has become the mainstream, it can not only a-si, SiN., n+ a-si continuous operation, but also the inverted gate can be used as a shading layer (no need to set up another shading layer), which is important for a-si TFT, because a-si is sensitive to light, once there is light inflow caused by leakage current increase, will lead to deterioration of image quality.
