Thin Film Transistor Substrate Hydrogen Occlusion Gate Electrode
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Solution Overview
Problem
In liquid crystal display devices, excessive hydrogen in the channel layer of thin film transistor substrates leads to high carrier density, making it difficult to achieve practical threshold voltage and reliable operation, as excessive hydrogen supply from insulating films can result in poor TFT characteristics and inability to turn off the transistor at practical voltages.
Innovation Solution
A thin film transistor substrate with a gate electrode having hydrogen occlusion capability and a semiconductor layer with controlled hydrogen concentration, where the gate electrode is made of an Al alloy with N, and the semiconductor layer has a specific hydrogen concentration range, inhibiting hydrogen diffusion and maintaining stable carrier density during manufacturing and operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating film containing hydrogen is formed on the insulating film containing oxygen to supply hydrogen to the channel layer, then defects or uncombined bonds are terminated and mobility is improved, but excessive hydrogen is supplied to the channel layer causing carrier density to become high and threshold voltage to drop below -10V making turning off impossible at practical voltages
Solution Approach 1:
A hydrogen barrier layer is introduced as an intermediary between the insulating film containing oxygen and the channel layer. This barrier layer selectively blocks excessive hydrogen diffusion while allowing controlled hydrogen supply to terminate defects in the channel layer, thus preventing carrier density from becoming too high while still improving mobility
Solution Approach 2:
The hydrogen barrier layer changes the hydrogen concentration parameter in the channel layer by blocking excessive hydrogen supply. This parameter control ensures that hydrogen concentration remains within an optimal range to maintain both improved mobility from defect termination and acceptable carrier density for practical threshold voltage operation
2Reliability
If hydrogen is supplied to the channel layer to terminate uncombined bonds, then carrier density decreases and TFT characteristics improve, but excessive hydrogen supply makes carrier density too high and threshold voltage too low for practical operation
Solution Approach 1:
The hydrogen barrier layer acts as a mediator that controls the hydrogen supply process. It allows sufficient hydrogen to reach the channel layer to terminate uncombined bonds and improve initial characteristics, while blocking excessive hydrogen that would otherwise raise carrier density too high and prevent practical turning off operation
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 substrate achieves practical threshold voltage and reliable TFT operation by occluding hydrogen, preventing excessive hydrogen concentration in the semiconductor layer, thereby improving off characteristics and reliability.
Implementation Method 1
the gate electrode has hydrogen occlusion capability of 2.5×10^20 atoms/cm³ to 2×10^22 atoms/cm³
Data Source
AI summary
A thin film transistor substrate includes: a plurality of pixels arranged in a matrix, each of the pixels including: a thin film transistor including: a gate electrode made of a metal and disposed on the substrate; a gate insulating film covering at least the gate electrode; a semiconductor layer including an oxide semiconductor provided at a position facing the gate electrode with the gate insulating film interposed therebetween; a source electrode and a drain electrode in contact with the semiconductor layer; and an interlayer insulating film provided on at least the semiconductor layer, the source electrode, and the drain electrode; and a pixel electrode electrically connected to the drain electrode. The gate electrode has hydrogen occlusion capability of 2.5×1020 to 2×1022 atoms/cm3, and the semiconductor layer has a hydrogen concentration of 1×1016 atoms/cm3 or less.