Oxide TFT Gate Stack Layout for Stable Short-Channel Characteristics
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Solution Overview
Problem
Forming a stable intermediate region between the channel and the drain/source in oxide semiconductor TFTs is challenging, especially when the channel length is short, leading to potential depletion and unstable TFT characteristics due to hydrogen diffusion.
Innovation Solution
A display device structure with a gate insulating film, an aluminum oxide film, and side spacers is used, where the gate electrode length is shorter than the aluminum oxide film, forming an intermediate region in the oxide semiconductor film to control hydrogen diffusion and maintain stable resistance levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrogen is supplied to the drain and source regions to decrease their resistance, then the conductivity of drain and source is improved, but the channel region becomes depleted and TFT characteristics become unstable
Solution Approach 1:
The patent applies local quality by creating distinct hydrogen concentration zones: the drain and source regions have high hydrogen concentration for low resistance, while the channel region maintains low hydrogen concentration to avoid depletion. This is achieved through selective hydrogen supply methods such as plasma treatment or chemical vapor deposition that target only the drain and source areas, preserving channel integrity while improving contact resistance.
Solution Approach 2:
The patent introduces an intermediary approach by using a gate insulating film with controlled hydrogen permeability. This film acts as a barrier that allows hydrogen to reach the drain and source regions while preventing excessive hydrogen diffusion into the channel region. The gate insulating film thus mediates between the need for conductive drain/source regions and the need to preserve channel characteristics.
2Productivity
If the channel length is shortened to increase transistor density, then the productivity is improved, but the TFT becomes prone to depletion and characteristics become unstable
Solution Approach 1:
The patent applies local quality by creating distinct hydrogen concentration zones: the drain and source regions have high hydrogen concentration for low resistance, while the channel region maintains low hydrogen concentration to avoid depletion. This is achieved through selective hydrogen supply methods such as plasma treatment or chemical vapor deposition that target only the drain and source areas, preserving channel integrity while improving contact resistance.
Solution Approach 2:
The patent applies preliminary action by pre-forming the gate insulating film with appropriate hydrogen barrier properties before hydrogen supply to the drain and source regions. This preliminary structure prevents excessive hydrogen diffusion into the channel region, ensuring that even when channel length is shortened for higher density, the channel remains protected from depletion and maintains stable characteristics.
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
This structure stabilizes the TFT characteristics by controlling hydrogen diffusion, reducing the risk of channel conductance and fluctuating Vd-Id characteristics, especially in short channel lengths, thereby enhancing the reliability of oxide semiconductor TFTs.
Implementation Method 1
hydrogen is supplied to the drain region and the source region to give conductivity in those regions... diffuse the hydrogen, which is in the drain and the source, into the region between the channel and the drain
Data Source
AI summary
The purpose of the present invention is to decrease the resistance of the drain and source in the TFT of the oxide semiconductor as well as to have stable Vd-Id characteristics of the TFT. The structure of the present invention is as follows: A display device having plural pixels including thin film transistors (TFT) having oxide semiconductor films comprising: a gate insulating film formed on the oxide semiconductor film, an aluminum oxide film formed on the gate insulating film, a gate electrode formed on the aluminum oxide film, a side spacer formed on both sides of the gate electrode, and an interlayer insulating film formed on the gate electrode, the side spacer, a drain and a source, wherein in a plan view, and in a direction from the drain to the source, a length of the gate electrode is shorter than a length of the aluminum oxide film.