LTPS TFT Light Shield Raised Section for Channel Width
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Solution Overview
Problem
Existing low temperature poly-silicon thin-film transistors (TFTs) face challenges in increasing driving power for high definition displays without reducing the aperture ratio, as increasing channel width or shortening channel length poses design limitations and risks.
Innovation Solution
A low temperature poly-silicon TFT design featuring a light shield layer with a raised section on the substrate, along with specific layer thicknesses and materials, allows for an increased channel width without affecting the aperture ratio, enhancing the width-to-length ratio and open state current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the channel width W is increased to increase the open state current, then the open state current ID is improved, but the aperture ratio of the display device is decreased
Solution Approach 1:
The patent introduces a third dimension by forming a raised section on the light shield layer, allowing the active layer to extend vertically. This enables the channel width to be increased in the vertical dimension without occupying additional horizontal space, thereby maintaining the aperture ratio while improving the open state current.
Solution Approach 2:
The light shield layer is segmented into a planar section and a raised section, with different heights creating distinct functional zones. The raised section provides additional area for the active layer while the planar section maintains the original device structure, allowing independent optimization of current drive and aperture ratio.
2Power
If the channel length L is shortened to increase the width-to-length ratio, then the open state current ID is improved, but the risk of channel breakdown is increased
Solution Approach 1:
Instead of shortening the channel length in the horizontal plane, the patent extends the channel width in the vertical dimension through the raised section. This maintains an adequate channel length for reliability while achieving the desired width-to-length ratio improvement through vertical expansion.
3Power
If the channel width W is increased to enhance driving power, then the driving power is improved, but the design flexibility of the panel is reduced
Solution Approach 1:
The raised section structure allows channel width expansion in the vertical dimension without consuming horizontal design space. This maintains panel design flexibility for other components while achieving enhanced driving power through increased channel width in the vertical direction.
Data Source
AI summary
The present invention provides a low temperature poly-silicon thin-film transistor, as well as a manufacturing method thereof, which includes: a substrate (1), a light shield layer (2) formed on the substrate (1), a pad layer (3) formed on the light shield layer (2), a dielectric layer (4) formed on the pad layer, an active layer (5) formed on the dielectric layer, a gate insulation layer (6) formed on the active layer (5), and a gate layer (7) formed on the gate insulation layer (6). The light shield layer (2) includes a planar section (21) formed on the substrate (1) and a raised section (22) formed on the planar section (21). The active layer (5) has a projection that covers at least a partial area of an upper surface of the raised section (22) and one of sidewalls (224) of the raised section (22). Without varying an aperture ratio of a display device, the channel width can be effectively increased and the width-to-length ratio can be increased so as to increase an open state current and enhance driving power of the LTPS TFT and device performance.