TFT Array Substrate Asymmetric Source Electrode Dislocation
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Solution Overview
Problem
In Thin-Film Transistor Liquid Crystal Displays (TFT-LCDs), process instability can cause dislocation between metal layers, leading to variations in parasitic capacitance across adjacent pixel units, resulting in non-uniform gray scales and poor picture quality, such as flicker and Mura.
Innovation Solution
The array substrate is designed with a thin film transistor (TFT) where the source and gate electrodes are structured to maintain a constant overlapping area, even with dislocation between metal layers, ensuring uniform parasitic capacitance and gray scale across adjacent pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional TFT structure with overlapping source and gate electrodes is used, then parasitic capacitance is formed for switching function, but dislocation between metal layers causes variation in parasitic capacitance leading to non-uniform gray scale and poor picture quality
Solution Approach 1:
The source electrode is designed with asymmetric structure where one end extends beyond the gate electrode while the other end is positioned differently, creating different overlapping areas at each end. This asymmetric design compensates for dislocation variations, maintaining consistent parasitic capacitance and uniform gray scale across pixels despite manufacturing alignment variations.
Solution Approach 2:
The patent modifies the geometric parameters of the source electrode, specifically its length and position relative to the gate electrode, to optimize the overlapping area. By adjusting these parameters, the design achieves stable parasitic capacitance values that are insensitive to metal layer dislocation, thereby improving picture quality uniformity.
2Reliability
If larger overlapping area between source and gate electrodes is used, then parasitic capacitance increases for better switching, but voltage jump on pixel electrode increases causing gray scale non-uniformity
Solution Approach 1:
The source electrode employs different overlapping lengths at its two ends relative to the gate electrode. One end has a longer overlap to provide sufficient parasitic capacitance for switching, while the other end has a shorter overlap to limit voltage jump. This local differentiation optimizes both switching performance and gray scale uniformity.
Data Source
AI summary
The invention relates to an array substrate for a display device and to a method for manufacturing an array substrate comprising a thin-film transistor (“TFT”). An array substrate according to an embodiment of the invention comprises a source electrode, a gate electrode and a drain electrode, wherein the gate electrode is located on a first metal layer, the source electrode and the drain electrode are located on a second metal layer, and in the case that dislocation occurs between the first metal layer and the second metal layer, the area of the overlapping region between the source electrode and the gate electrode keeps constant.