Oxide Semiconductor Thin Film Transistor Array Substrate
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Solution Overview
Problem
Conventional liquid crystal display (LCD) thin film transistor array substrates face challenges in achieving high charge mobility and uniform electrical characteristics, especially in large display devices, due to limitations in amorphous and polycrystalline silicon thin film transistors.
Innovation Solution
A thin film transistor array substrate is developed with an oxide semiconductor layer comprising a lower oxide layer with low oxygen concentration and an upper oxide layer with high oxygen concentration, enhancing charge mobility and threshold voltage, allowing for improved semiconductor characteristics and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If amorphous silicon thin film transistors are used, then uniform electrical characteristics can be achieved, but charge mobility is low
Solution Approach 1:
The patent changes the material parameter from conventional silicon-based semiconductors to oxide semiconductor (IGZO), which fundamentally alters the electrical properties to achieve high charge mobility while maintaining uniform characteristics through controlled oxygen concentration gradients in the semiconductor layer
Solution Approach 2:
The patent employs a composite structure with multiple oxide layers having different oxygen concentrations (first oxide layer with lower oxygen concentration, second oxide layer with higher oxygen concentration), creating a composite oxide semiconductor material that simultaneously achieves high mobility and uniformity
2Speed
If polycrystalline silicon thin film transistors are used, then charge mobility is high, but uniform electrical characteristics are difficult to achieve in large display devices
Solution Approach 1:
The patent transitions from polycrystalline silicon to oxide semiconductor material, changing the fundamental material parameters to achieve high charge mobility inherent to oxide semiconductors while the amorphous nature allows uniform deposition across large areas
Solution Approach 2:
The patent applies local quality by creating different oxygen concentration zones within the oxide semiconductor layer - the first oxide layer has lower oxygen concentration for high mobility, while the second oxide layer has higher oxygen concentration for stability and uniformity, with each layer serving a specific functional purpose
3Reliability
If additional ohmic contact layers or light blocking layers are added, then electrical characteristics can be improved, but device complexity increases
Solution Approach 1:
The patent makes the oxide semiconductor layer multi-functional by designing it to simultaneously serve as the semiconductor channel layer and provide inherent ohmic contact properties through its specific oxygen concentration composition, eliminating the need for separate ohmic contact layers
Solution Approach 2:
The patent extracts and eliminates unnecessary layers (ohmic contact layers and light blocking layers) by incorporating their functions directly into the oxide semiconductor layer itself, simplifying the overall device structure while maintaining performance
Data Source
AI summary
A thin film transistor array substrate having a high charge mobility and that can raise a threshold voltage, and a method of fabricating the thin film transistor array substrate are provided. The thin film transistor array substrate includes: an insulating substrate; a gate electrode formed on the insulating substrate; an oxide semiconductor layer comprising a lower oxide layer formed on the gate electrode and an upper oxide layer formed on the lower oxide layer, such that the oxygen concentration of the upper oxide layer is higher than the oxygen concentration of the lower oxide layer; and a source electrode and a drain electrode formed on the oxide semiconductor layer and separated from each other.