Gate Driver TFT Structure for Stable In-Cell Touch Displays
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Solution Overview
Problem
In-cell-type touch panels incorporating a GDM circuit with oxide semiconductor TFTs face various issues, including charge withdrawal from internal nodes and threshold voltage shifts that affect the functionality and power consumption of the gate driver circuit.
Innovation Solution
The display device incorporates a scan signal line drive circuit with a shift register circuit comprising thin film transistors, where the second transistor has a dual-gate structure with an upper and lower gate electrode configuration, connected to HIGH and LOW power supply lines respectively, to stabilize the internal node potential and prevent threshold voltage shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If an in-cell-type touch panel includes a GDM circuit with oxide semiconductor TFTs, then the touch panel achieves thinness and lightweight design, but charge withdrawal from internal nodes occurs causing threshold voltage shifts
Solution Approach 1:
The gate electrode of the second transistor is divided into two separate gates (first gate and second gate), allowing independent control of channel formation and charge storage. This segmentation enables the first gate to form the channel while the second gate stores charge, preventing charge withdrawal from the internal node and eliminating threshold voltage shifts.
Solution Approach 2:
The invention transitions from a conventional single-gate structure to a dual-gate structure, adding a dimensional aspect to the gate control. The first gate electrode is positioned at one interface of the semiconductor layer while the second gate electrode is positioned at the opposite interface, creating a three-dimensional charge control mechanism that stabilizes the internal node potential.
2Ease of manufacture
If oxide semiconductor TFTs are used in the GDM circuit, then manufacturing simplicity is improved, but charge withdrawal and threshold voltage shifts occur
Solution Approach 1:
By segmenting the gate electrode into two independent gates, the invention maintains the ease of manufacturing oxide semiconductor TFTs while adding the functional capability to prevent charge withdrawal. The dual-gate structure can be integrated into existing oxide semiconductor fabrication processes.
Solution Approach 2:
The invention changes the electrical parameters of the transistor by introducing a second gate that can independently control the channel. This parameter change enables precise control over charge storage and channel formation, stabilizing the internal node potential without compromising manufacturing simplicity.
3Device complexity
If a conventional single-gate TFT structure is used, then device complexity is reduced, but charge withdrawal from internal nodes causes functionality issues
Solution Approach 1:
The gate electrode is segmented into two independent gates, which increases device complexity slightly but resolves the functionality issues by preventing charge withdrawal. The first gate forms the channel while the second gate stores charge, ensuring proper gate driver circuit operation.
Solution Approach 2:
The dual-gate structure provides multi-functionality within a single transistor, where the first gate handles channel formation and the second gate handles charge storage. This universal design improves reliability while maintaining reasonable device complexity.
Data Source
AI summary
A display device includes: a display panel including a HIGH power supply line and a LOW power supply line; and a scan signal line drive circuit including a unit circuit, wherein the unit circuit includes: a SET terminal; a RESET terminal; an output terminal; a first thin film transistor; a second thin film transistor including a second semiconductor layer, a second gate electrode, a second source electrode, and a second drain electrode, the second gate electrode being electrically connected to the SET terminal, one of the second source electrode and the second drain electrode being electrically connected to an internal node; and a third thin film transistor, the second gate electrode is an upper gate electrode, another one of the second source electrode and the second drain electrode is electrically connected to the HIGH power supply line, and the second thin film transistor further includes a lower gate electrode.