Active Matrix Substrate Dual-Layer Holes for TFT Impurity Discharge
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Solution Overview
Problem
In the manufacturing process of TFT substrates for liquid crystal display devices, impurities such as moisture easily infiltrate into the organic insulating layer, leading to potential display failures due to changes in the threshold voltage and increased off-leak current of the pixel TFTs.
Innovation Solution
The implementation of an active matrix substrate with a dual-layer hole structure in the organic and inorganic insulating layers, which includes through-holes in the inorganic insulating layer and bottomed holes in the organic insulating layer, allows for the efficient discharge of impurities to the outside, thereby suppressing fluctuations in the characteristics of the oxide semiconductor TFTs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an organic insulating layer is formed thickly to achieve sufficient flattening effect and load capacitance reduction, then the flattening effect and load capacitance reduction are improved, but impurities such as moisture easily infiltrate into the organic insulating layer and cannot be discharged, leading to threshold voltage shift and increased off-leak current
Solution Approach 1:
The patent introduces a porous inorganic insulating layer with controlled porosity (30-70%) that allows impurities to be discharged while maintaining the flattening effect. The porous structure provides channels for moisture and other impurities to escape without compromising the thick organic insulating layer's flattening capability
Solution Approach 2:
The patent segments the insulating structure into multiple functional layers: a thick organic insulating layer for flattening, a porous inorganic insulating layer for impurity discharge, and additional inorganic insulating layers for protection. This segmentation allows each layer to perform its specific function optimally
2Reliability
If an inorganic insulating layer is provided on the organic insulating layer to insulate pixel electrodes, then the insulation between pixel electrodes is improved, but impurities infiltrating into the organic insulating layer are trapped and cannot be discharged to the outside
Solution Approach 1:
The patent replaces the conventional dense inorganic insulating layer with a porous inorganic insulating layer that has controlled porosity (30-70%). This porous structure maintains the insulation function between pixel electrodes while providing channels for impurities to discharge from the organic insulating layer to the outside
Solution Approach 2:
The porous inorganic insulating layer acts as an intermediary between the organic insulating layer and the external environment. It allows impurities to pass through while maintaining the insulation barrier for pixel electrodes, serving dual functions simultaneously
3Manufacturing precision
If the organic insulating layer thickness is increased in high-resolution liquid crystal display devices (1000 ppi or more), then the flattening effect is improved, but the volume of the organic insulating layer increases and the influence of impurities becomes more significant
Solution Approach 1:
The patent introduces a porous inorganic insulating layer specifically designed to work with thick organic insulating layers in high-resolution displays. The porous structure provides impurity discharge channels that scale with the increased organic layer thickness, preventing impurity accumulation even as the organic layer volume increases
Solution Approach 2:
The patent adds a new dimensional aspect to the insulating layer structure by introducing porosity as a key parameter. This creates a three-dimensional network of discharge channels within the inorganic insulating layer, enabling impurity removal from the expanded organic insulating layer volume
Data Source
AI summary
An active matrix substrate includes a substrate, a pixel TFT that is supported by the substrate, provided corresponding to each of a plurality of pixel areas, and includes an oxide semiconductor layer, an organic insulating layer disposed above at least the oxide semiconductor layer of the pixel TFT, and an inorganic insulating layer disposed in contact with an upper surface of the organic insulating layer on the organic insulating layer. The organic insulating layer and the inorganic insulating layer are provided with a plurality of dual-layer hole structure portions, each of the dual-layer hole structure portions includes a through-hole provided in the inorganic insulating layer and a bottomed hole provided in the organic insulating layer and positioned below the through-hole, and the through-hole is positioned on an inner side of an outer edge of the bottomed hole when viewed from a normal direction of the substrate.