Thin-Film Transistor Offset Structure for Stable Oxide TFT Mobility
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Solution Overview
Problem
Thin film transistors (TFTs) face limitations in manufacturing due to issues with manufacturing cost, process complexity, and uniformity, particularly in large-area displays, and struggle to balance electrical stability and mobility, especially in oxide semiconductor TFTs where the conductivity-providing region's mobility varies with sheet resistance and is influenced by insulation layers.
Innovation Solution
A thin film transistor design with a conductivity-providing part formed through doping without patterning the gate insulation layer, featuring an active layer with an offset part between the channel and conductivity-providing parts, and a gate insulation layer covering the entire active layer except for contact regions, to secure electrical stability and minimize insulation layer influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate insulation layer is formed to cover only the channel part of the active layer, then the manufacturing process is simpler, but the transistor exhibits poor electrical characteristics due to direct contact between the conductivity-providing part and gate electrode
Solution Approach 1:
The gate insulation layer is segmented into different coverage areas: it covers the channel part to ensure proper electrical characteristics, while intentionally exposing the conductivity-providing part to enable direct contact with the gate electrode for enhanced charge injection. This selective segmentation resolves the contradiction by applying different coverage rules to different functional regions of the active layer.
Solution Approach 2:
The gate insulation layer applies different local qualities to different regions: full coverage over the channel part for electrical stability, and no coverage over the conductivity-providing part for direct electrical contact. This local differentiation allows the structure to simultaneously achieve good electrical characteristics and proper charge injection functionality.
2Reliability
If the gate insulation layer covers the entire active layer including conductivity-providing parts, then electrical characteristics improve, but contact between conductivity-providing part and gate electrode is blocked
Solution Approach 1:
The gate insulation layer is segmented to cover only the channel part while leaving the conductivity-providing part exposed. This segmentation allows the channel to maintain good electrical characteristics through insulation coverage, while the exposed conductivity-providing part enables efficient charge injection directly to the gate electrode, resolving the contradiction between electrical stability and charge injection efficiency.
Solution Approach 2:
The offset part of the active layer acts as an intermediary structure that positions the channel part under the gate electrode while keeping the conductivity-providing part exposed. This intermediary arrangement allows the gate insulation layer to cover the channel for electrical stability while permitting direct contact between the conductivity-providing part and gate electrode for efficient charge injection.
3Productivity
If dopant concentration in conductivity-providing part is increased to improve charge injection, then charge injection efficiency improves, but threshold voltage control becomes difficult
Solution Approach 1:
Different dopant concentrations are applied to different regions: the conductivity-providing part has high dopant concentration for efficient charge injection, while the channel part has controlled lower dopant concentration for proper threshold voltage control. This local quality differentiation resolves the contradiction by allowing high productivity in the conductivity-providing region without compromising manufacturing precision in the channel region.
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 design enhances electrical stability and mobility, prevents leakage currents, and maintains effective channel width, allowing for efficient manufacturing and improved performance in display applications by adjusting the size of the photoresist pattern to form the offset part between the conductivity-providing and channel parts of the semiconductor layer.
Implementation Method 1
the conductivity-providing part may be doped with a dopant
Data Source
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AI summary
An embodiment of the present disclosure provides a thin film transistor (100), a method of manufacturing the thin film transistor and a display apparatus including the thin film transistor. The thin film transistor includes an active layer (130) on a substrate (110), a gate electrode (140) disposed apart from the active layer to at least partially overlap the active layer, and a gate insulation layer (150) between the active layer and the gate electrode. The gate insulation layer may cover a whole top surface of the active layer facing the gate electrode. The active layer may include a channel part (131) overlapping the gate electrode, a conductivity-providing part (133a, 133b) which does not overlap the gate electrode, and an offset part (132a, 132b) between the channel part and the conductivity-providing part. The offset part may not overlap the gate electrode, and the conductivity-providing part may be doped with a dopant.