Thin-Film Transistor Hydrogen Blocking Layer
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Solution Overview
Problem
The challenge in manufacturing thin-film transistors with oxide semiconductor layers, such as IGZO, is controlling the diffusion length of hydrogen during the plasma process, which affects the resistance of the source, drain, and channel regions, making it difficult to form transistors of short length and reducing the reliability of flat panel display devices.
Innovation Solution
Incorporating a hydrogen blocking layer with low hydrogen concentration between the oxide semiconductor layer and the undercoat layer, which blocks hydrogen diffusion and allows for precise control of the channel region length, thereby reducing the transistor size and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plasma process using the gate electrode as a mask is used to reduce the resistance of source and drain regions, then the resistance of source and drain regions is reduced, but the diffusion length of hydrogen cannot be controlled, causing hydrogen to enter the channel region and increasing its resistance
Solution Approach 1:
A hydrogen blocking layer is introduced as an intermediary between the gate electrode and the oxide semiconductor layer. This blocking layer selectively prevents hydrogen diffusion into the channel region while allowing the plasma process to continue reducing resistance in the source and drain regions. The blocking layer acts as a mediator that separates the conflicting requirements of low source/drain resistance and controlled hydrogen diffusion.
Solution Approach 2:
The oxide semiconductor layer is segmented into distinct functional regions: source region, drain region, and channel region. The hydrogen blocking layer is positioned to selectively protect only the channel region from hydrogen diffusion, while the source and drain regions remain exposed to the plasma process for resistance reduction. This spatial segmentation allows different regions to have different hydrogen concentrations and electrical properties.
2Productivity
If the diffusion length of hydrogen is not controlled, then the resistance of source and drain regions can be reduced, but the channel region resistance increases, making it difficult to form transistors of short length
Solution Approach 1:
The hydrogen blocking layer serves as a mediator that enables the use of shorter channel lengths by preventing hydrogen contamination. With the blocking layer in place, hydrogen diffusion is controlled, allowing the channel region to be made shorter without suffering from increased resistance due to hydrogen entry. This enables higher productivity through faster transistor switching speeds.
3Ease of manufacture
If hydrogen diffusion is not controlled, then the manufacturing process is simpler, but the transistor reliability under gate bias temperature stress is reduced
Solution Approach 1:
The hydrogen blocking layer is introduced as a simple intermediary structure that provides reliable hydrogen diffusion control. While it adds one additional layer to the manufacturing process, it significantly improves transistor reliability under gate bias temperature stress by preventing hydrogen-induced degradation. The blocking layer can be formed using standard sputtering or CVD techniques, keeping the process relatively simple.
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 approach allows for the formation of compact and highly reliable thin-film transistors by preventing hydrogen entry into the channel region, improving durability under gate bias temperature stress and enabling the use of oxide semiconductor layers in larger area displays with reduced current consumption.
Implementation Method 1
a hydrogen blocking layer having a hydrogen concentration lower than that in the hydrogenated layer; the hydrogen blocking layer separates the hydrogenated layer and the channel region of the oxide semiconductor layer
Implementation Method 2
this oxide semiconductor layer is formed by a process using hydrogen plasma
Implementation Method 3
this plasma process makes it difficult to control the diffusion length of hydrogen
Data Source
AI summary
According to one embodiment, a thin-film transistor and a method of manufacturing the same achieve size reduction of the thin-film transistor while using an oxide semiconductor layer. The oxide semiconductor layer includes a channel region, a source region, and a drain region. A gate electrode is arranged at a position spaced from the channel region of the oxide semiconductor layer so as to face the channel region. A source electrode is electrically connected to the source region of the oxide semiconductor layer. A drain electrode is electrically connected to the drain region of the oxide semiconductor layer. An undercoat layer adjoins the source region and the drain region of the oxide semiconductor layer. A hydrogen blocking layer has a hydrogen concentration lower than that in the undercoat layer and separates the undercoat layer and the channel region of the oxide semiconductor layer.