Array Substrate Insulating Layer Design for Capacitance and Transmittance
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Solution Overview
Problem
Conventional liquid crystal display (LCD) array substrates with silicon oxide as the dielectric layer of the storage capacitor are sensitive to static electricity and have limited capacitance due to thin gate-insulating layers, which also affect the transmittance and characteristics of thin-film transistors (TFTs).
Innovation Solution
The array substrate design incorporates a first insulating layer with high hydrogen content, made of silicon nitride, in the transistor and capacitor areas, and a second insulating layer with lower hydrogen content, made of silicon oxide, in the light transmittance area, to enhance capacitance and transmittance while preventing static electricity issues. This configuration includes a transparent electrode in the light transmittance area and uses a half-tone mask for precise patterning to exclude the insulating layer from the transmittance area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a gate-insulating layer is used as the dielectric layer of the storage capacitor, then the capacitance of the storage capacitor can be increased by making the thickness small, but the structure becomes sensitive to static electricity
Solution Approach 1:
The patent uses a composite insulating layer structure combining silicon oxide and silicon nitride layers. The silicon oxide layer provides good interface characteristics with the semiconductor layer, while the silicon nitride layer provides high dielectric constant for increased capacitance and hydrogen content for passivating defects, thereby reducing static electricity sensitivity while maintaining high capacitance
2Quantity of substance
If silicon nitride is used as the insulating layer to increase capacitance, then the capacitance increases, but the light transmittance decreases
Solution Approach 1:
The patent applies different insulating layer configurations to different regions of the substrate. In the light transmittance area, only a thin silicon oxide layer is formed to maintain high light transmittance. In the transistor and capacitor areas, a composite structure with silicon nitride layer is formed to provide high capacitance. This local differentiation resolves the contradiction between capacitance enhancement and light transmittance maintenance
3Reliability
If a thick insulating layer is formed to prevent static electricity, then static electricity sensitivity is reduced, but the capacitance of the storage capacitor decreases
Solution Approach 1:
The patent changes the dielectric constant parameter by introducing silicon nitride material with high dielectric constant (k≈7) into the insulating layer structure. This allows achieving the required capacitance value with a thinner physical layer thickness, thereby maintaining both high capacitance and static electricity resistance through optimized layer composition rather than simply increasing thickness
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution increases the capacitance of the capacitor and improves the characteristics of TFTs and light transmittance, while preventing static electricity issues and maintaining high transmittance by using silicon nitride as the dielectric layer and silicon oxide in the light transmittance area, respectively.
Implementation Method 1
hydrogen that is comprised in the first insulating layer may fill a defect site of the polysilicon and then may solve the defect site
Implementation Method 2
the first insulating layer may include a material having a first light transmittance, and the second insulating layer may include a material having a second light transmittance that is different from the first light transmittance. The material of the first light transmittance, and the material of the second light transmittance may be silicon nitride and silicon oxide, respectively
Data Source
AI summary
An array substrate is disclosed. In one embodiment, the substrate includes 1) a transistor area in which a transistor is formed, 2) a capacitor area in which a capacitor is formed, wherein the capacitor is electrically connected to the transistor and 3) a light transmittance area adjacent to at least one of the transistor area and the capacitor area. The substrate further includes 1) a first insulating layer formed in at least one of the transistor area and the capacitor area, wherein the first insulating layer is not formed in the light transmittance area and 2) a second insulating layer having i) a first portion arranged to substantially overlap with the first insulating layer in the at least one area, and ii) a second portion formed in the light transmittance area.