Thin Film Transistor With Segmented Oxide Channel
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Solution Overview
Problem
Current thin film transistors (TFTs) with oxide semiconductor channel layers face limitations in reducing channel length below the resolution limit of exposure devices, resulting in only minor improvements in current driving force, and are costly to manufacture, especially for large substrates.
Innovation Solution
A TFT design with an oxide semiconductor channel layer featuring two regions of different resistance values, where the higher resistance region acts as the channel, and metal electrodes that reduce the oxide semiconductor layer and supply hydrogen, allowing for a shorter effective channel length and improved current driving force while maintaining cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the channel length is shortened to increase current driving force, then the current driving force is improved, but the channel length cannot be made shorter than the resolution limit of the exposure device (3-4 μm when using g-line+h-line exposure device)
Solution Approach 1:
The patent applies local quality by creating regions with different resistance values within the oxide semiconductor layer. Specifically, it forms low-resistance regions beneath the source and drain electrodes while maintaining a high-resistance channel region between them. This spatial differentiation of resistance properties allows the electrical channel length to be shorter than the physical distance between source and drain electrodes, thereby increasing current driving force without being constrained by exposure device resolution limits.
2Manufacturing precision
If the i-line exposure device is used to shorten channel length to 1.5 μm, then the channel length is reduced, but the manufacturing cost increases significantly
Solution Approach 1:
The patent changes the electrical parameters of the oxide semiconductor layer by controlling its resistance distribution. By forming low-resistance regions beneath the source and drain electrodes through specific manufacturing processes (such as titanium electrode formation and heat treatment), the effective electrical channel length is reduced without changing the physical channel length defined by photolithography. This allows continued use of cost-effective g-line+h-line exposure devices while achieving shorter effective channel lengths.
3Reliability
If only contact resistance is reduced by lowering the resistance of oxide semiconductor beneath source and drain electrodes, then contact resistance is improved, but the channel length remains 3-4 μm and current driving force is improved by only a few percent
Solution Approach 1:
The patent segments the oxide semiconductor layer into distinct functional regions with different resistance values. It creates low-resistance regions beneath the source and drain electrodes for good contact, while maintaining a high-resistance channel region between them. This segmentation allows the electrical channel length to be defined by the high-resistance region only, which can be shorter than the physical distance between source and drain electrodes, thereby significantly increasing current driving force beyond what contact resistance reduction alone can achieve.
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 design significantly enhances the current driving force of TFTs by shortening the electrical channel length and improving manufacturing efficiency, enabling high frame rate and high definition displays with reduced power consumption.
Implementation Method 1
metal electrodes that reduce the oxide semiconductor layer and supply hydrogen
Implementation Method 2
metal electrodes that reduce the oxide semiconductor layer
Data Source
AI summary
The invention provides a thin film transistor having current driving force that can be substantially improved. By heat treatment, the IGZO layer (45) from which oxygen is taken away by the titanium electrodes (65) becomes the low resistance regions (40b), and the IGZO layer (45) from which oxygen is not taken away remains as the high resistance region (40a). In this state, when the gate voltage is applied to the gate electrode (20), electrons in the low resistance regions (40b) near the boundaries with the high resistance region (40a) move respectively to the titanium electrode (65) sides. As a result, the length of the low resistance regions (40b) becomes short, and oppositely, the length of the high resistance region (40a) becomes longer by the size of the shortened low resistance regions. However, the electrical channel length (Le) becomes shorter than the source/drain interval space (Lch) as the limit resolution of the exposure device, and the current driving force becomes large.