Donut-Shaped Oxide Semiconductor TFT Sensor for Touch Detection
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Solution Overview
Problem
Thin-film transistors (TFTs) with amorphous silicon active layers have low charge mobility, while polycrystalline silicon TFTs require complex and costly manufacturing processes. There is a need for a TFT sensor that can stably detect touch intensity and direction with improved performance.
Innovation Solution
A thin-film transistor sensor with a donut-shaped active layer including an oxide semiconductor, featuring a separation hole at its center, etch stop layers with contact holes, and strategically positioned source and drain electrodes, along with top and bottom gate electrodes that control current direction through periodic voltage application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous silicon is used as the active layer material, then the manufacturing process is simple, but the charge mobility is very low (about 0.5 cm2/Vs)
Solution Approach 1:
The patent changes the material parameter of the active layer from conventional amorphous silicon or polycrystalline silicon to oxide semiconductor (such as IGZO - Indium Gallium Zinc Oxide). This material substitution maintains the simplicity of the manufacturing process while dramatically improving charge mobility to about 10-100 cm2/Vs, resolving the contradiction between ease of manufacture and charge mobility performance.
2Reliability
If polycrystalline silicon is used as the active layer material, then the charge mobility is improved, but the manufacturing process becomes complicated and manufacturing cost increases due to required crystallization, impurity-implantation, and activation processes
Solution Approach 1:
The patent changes the material parameter to oxide semiconductor, which inherently provides high charge mobility without requiring complex crystallization processes. The oxide semiconductor active layer can be formed through simple sputtering or atomic layer deposition, eliminating the need for impurity-implantation and activation processes, thus resolving the contradiction between charge mobility improvement and manufacturing process complexity.
Solution Approach 2:
The patent adopts oxide semiconductor materials that can be processed at lower temperatures and with simpler equipment compared to polycrystalline silicon. This approach uses more accessible, less complex manufacturing tools to achieve the desired performance, reducing both process complexity and manufacturing cost while maintaining high charge mobility.
3Device complexity
If a conventional TFT structure is used, then the device structure is simple, but the ability to detect touch direction and intensity is insufficient
Solution Approach 1:
The patent segments the active layer into multiple independent channels by forming insulating partitions (such as silicon nitride layers) within the oxide semiconductor active layer. These partitions create separate current paths that can independently detect touches from different directions. By analyzing the current distribution across multiple channels, the system achieves precise touch direction and intensity detection while maintaining a relatively simple overall device structure.
Solution Approach 2:
The patent applies local quality by creating regions with different electrical properties within the active layer. The insulating partitions are strategically positioned to create channels with specific orientations, allowing each channel to be sensitive to touches from particular directions. This local differentiation of structural and electrical properties enables precise directional touch detection without requiring complete structural redesign.
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 sensor effectively senses touch direction and intensity by controlling current flow through multiple channels, offering improved performance and manufacturing simplicity compared to traditional TFTs.
Implementation Method 1
an active layer in a donut shape on the insulation layer, the active layer including a channel through which a current generated by a charged body flows
Implementation Method 2
A direction of current flowing in the channel may be controlled by applying a periodically-swinging voltage to the first and second top gate electrodes
Data Source
AI summary
According to an aspect of the present invention, there is provided a thin-film transistor (TFT) sensor, including a bottom gate electrode on a substrate, an insulation layer on the bottom gate electrode, an active layer in a donut shape on the insulation layer, the active layer including a channel through which a current generated by a charged body flows, an etch stop layer on the active layer, the etch stop layer including a first contact hole and a second contact hole, and a source electrode and a drain electrode burying the first and second contact holes, the source and drain electrodes being disposed on the etch stop layer so as to face each other.