TFT Substrate Active Layer Protrusion for Off Current Reduction
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Solution Overview
Problem
In liquid crystal displays (LCDs), thin film transistors (TFTs) experience off currents due to electron movement between the drain and source electrodes when they are off, leading to residual image issues, which are exacerbated by light influence and increased capacitive effects between gate, source, and drain electrodes.
Innovation Solution
The design minimizes off currents by extending the electron moving distance and optimizing the active layer exposure between source and drain electrodes, with specific protruding portions and overlapping areas to reduce electron trapping and capacitive influences, using a mask with light-shielding and translucent regions to control electrode formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the active layer is exposed in the channel region between source and drain electrodes, then electron movement is facilitated when TFT is on, but off current increases when TFT is off
Solution Approach 1:
The patent applies different properties to different regions of the active layer. The channel region between source and drain electrodes has the active layer exposed to facilitate electron movement when on, while the protruding portions extending beyond the channel region have the active layer covered or modified to prevent electron movement when off. This local differentiation resolves the contradiction between enabling conduction and preventing leakage.
Solution Approach 2:
The active layer is segmented into distinct functional zones: the channel region for conduction and the protruding portions for leakage prevention. By dividing the active layer into these segments with different exposure characteristics, the patent achieves both low off current and reliable switching performance simultaneously.
2Object-generated harmful factors
If the active layer protrudes outside the channel region, then electron moving distance is extended to reduce off current, but manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent performs preliminary patterning actions during the manufacturing process to pre-establish the exact protrusion dimensions of the active layer. By controlling the deposition and etching sequences in advance, the active layer protrusion is precisely defined before final assembly, making the electron moving distance controllable and reproducible while maintaining manufacturing precision.
3Object-generated harmful factors
If light-blocking structures are added to reduce light influence on TFT, then off current is minimized, but device complexity increases
Solution Approach 1:
The patent merges the light-blocking function with existing structural elements. The gate electrode and electrode overlapping regions serve dual purposes: electrical conduction control and light shielding. By combining these functions into existing structures rather than adding separate light-blocking components, the patent reduces light-induced off current while minimizing increases in device complexity.
Data Source
AI summary
A thin film transistor substrate, wherein the moving area of electrons between source and drain electrodes of a thin film transistor (TFT) is minimized, the moving distance of electrons is increased, and the sizes of capacitors defined by a gate electrode together with the respective source and drain electrodes are identical to each other so that an off current generated when the TFT is off can be minimized; a method of manufacturing the thin film transistor substrate; and a mask for manufacturing the thin film transistor substrate. Accordingly, it is possible to minimize an off current induced due to a phenomenon of electron trapping by light.