Flexible Array Substrate Gate Insulator Stabilization
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Solution Overview
Problem
The existing array substrates using flexible substrates face challenges in maintaining stable electrical properties due to low-temperature semiconductor layer formation, which results in threshold voltage shifts and deteriorated performance in thin film transistors, primarily because of inadequate dehydration and high localized defects in the gate insulating layer.
Innovation Solution
A double-layered gate insulating layer structure comprising aluminum oxide and hafnium oxide materials is used, with a hardening step at 350°C to ensure complete solvent removal, enhancing the density and interface quality between the oxide semiconductor layer and the insulating layer, thereby stabilizing the thin film transistor's switching and current-voltage properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a flexible substrate is used instead of glass substrate, then weight and flexibility are improved, but heat stability deteriorates causing limitations in fabrication temperature
Solution Approach 1:
The patent changes the material composition of the gate insulating layer to include aluminum oxide and hafnium oxide in specific ratios, and optimizes the hardening temperature parameter to 350°C or higher. This allows complete solvent removal and sufficient dehydration while remaining within the heat resistance limits of flexible substrates, thus resolving the contradiction between using flexible substrates and maintaining fabrication temperature stability.
2Temperature
If semiconductor layer is formed at low temperature on flexible substrate, then fabrication temperature constraint is satisfied, but electrical characteristics deteriorate due to low density
Solution Approach 1:
The patent performs preliminary dehydration of the gate insulating layer by controlling the hardening temperature to 350°C or higher before forming the semiconductor layer. This preliminary action removes solvents and reduces localized defects in the gate insulating layer, creating a high-quality interface that enables the semiconductor layer to achieve sufficient density and excellent electrical characteristics even when formed at low temperatures on flexible substrates.
3Temperature
If gate insulating layer is formed with soluble aluminum oxide material, then low temperature fabrication is enabled, but threshold voltage shifts occur due to insufficient dehydration
Solution Approach 1:
The patent changes the hardening temperature parameter to 350°C or higher, which is sufficient to completely remove solvents from the soluble aluminum oxide material and achieve adequate dehydration. This parameter change prevents the formation of localized defects and mobile charges in the gate insulating layer, thereby eliminating threshold voltage shifts while still allowing low-temperature fabrication compatible with flexible substrates.
Solution Approach 2:
The patent uses a composite gate insulating layer comprising aluminum oxide and hafnium oxide materials. This composite structure provides both the solubility needed for low-temperature processing and the thermal stability required for complete dehydration at 350°C or higher, preventing threshold voltage shifts while maintaining compatibility with flexible substrate fabrication.
4Temperature
If oxide semiconductor material is used, then low temperature formation is possible, but threshold voltage shifts occur due to interface quality issues with gate insulating layer
Solution Approach 1:
The patent performs preliminary dehydration of the gate insulating layer by controlling the hardening temperature to 350°C or higher before forming the oxide semiconductor layer. This preliminary action completely removes solvents and reduces localized defects in the gate insulating layer, creating a high-quality interface that prevents threshold voltage shifts while allowing the oxide semiconductor layer to be formed at low temperatures.
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 effectively prevents threshold voltage shifts and improves the reliability and electrical properties of thin film transistors, ensuring stable performance even under stress conditions, and allows for the use of flexible substrates in display devices.
Implementation Method 1
the substrate having the aluminum oxide material layer may be heated through a hardening step at a temperature of about 350° C.
Implementation Method 2
dehydration in the gate insulating layer of the soluble aluminum oxide material is not sufficiently performed by the hardening step of a temperature of about 350° C.
Implementation Method 3
When the oxide semiconductor layer is formed through a sputtering method, the gate insulating layer may be formed of silicon oxide or silicon nitride through a chemical vapor deposition (CVD) method.
Implementation Method 4
the gate insulating layer may be formed of silicon oxide or silicon nitride through a chemical vapor deposition (CVD) method.
Data Source
AI summary
An array substrate includes: a substrate; a gate line and a gate electrode on the substrate; a gate insulating layer on the gate line and the gate electrode, the gate insulating layer including a first insulator and a second insulator on the first insulator, wherein the first insulator includes an aluminum oxide material and has a first thickness, and the second insulator includes a hafnium oxide material and has a second thickness; an oxide semiconductor layer on the gate insulating layer over the gate electrode; a data line over the gate insulating layer; a source electrode and a drain electrode contacting the oxide semiconductor layer; a passivation layer on the data line, the source electrode and the drain electrode; and a pixel electrode on the passivation layer, the pixel electrode connected to a drain electrode through a drain contact hole.