Scan Driver Oxide TFT Composition for Bootstrapping Reliability
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Solution Overview
Problem
Existing scan drivers in display devices face challenges in maintaining consistent operating characteristics of thin-film transistors due to electrical stress from current amount or voltage bootstrapping, which affects reliability and electrical performance.
Innovation Solution
The scan driver incorporates a semiconductor layer composition for thin-film transistors using different oxide semiconductor materials for pull-up and pull-down nodes to reduce electrical stress and improve reliability, including a first active layer of indium-gallium-zinc-oxide and a second active layer of indium-gallium-zinc-tin oxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thin-film transistors use uniform semiconductor material for all nodes, then manufacturing process is simple, but electrical stress from current amount and voltage bootstrapping degrades reliability
Solution Approach 1:
The patent applies different oxide semiconductor materials to different transistor nodes based on their specific electrical stress conditions. The pull-up node uses a first oxide semiconductor material optimized for its electrical characteristics, while the pull-down node uses a second oxide semiconductor material suited for its different electrical stress profile. This localized material optimization resolves the contradiction by improving reliability through material differentiation while maintaining manufacturing feasibility through a systematic approach to material selection and deposition.
2Productivity
If thin-film transistors are subjected to voltage bootstrapping and high current, then driving capability is enhanced, but electrical stress deteriorates operating characteristics
Solution Approach 1:
The patent changes the material parameter of the semiconductor layer to different oxide semiconductor materials for pull-up and pull-down nodes. This material parameter change enables the transistors to withstand the electrical stress from voltage bootstrapping and high current while maintaining stable operating characteristics. The first oxide semiconductor material for the pull-up node and second oxide semiconductor material for the pull-down node are specifically selected to optimize performance under high-speed driving conditions without degrading reliability.
Data Source
AI summary
A scan driver includes stages which sequentially output scan signals to scan signal lines during an active period of an N-th frame, and at least one of the stages includes an output node controller that supplies a gate-on voltage to a pull-up node in response to a gate control signal of a display driver; and an output controller that outputs a scan signal to a scan signal line by outputting a scan clock signal to a scan signal line in case that the gate-on voltage is supplied to the pull-up node, wherein the output node controller includes a thin-film transistor including a first active layer, and directly or indirectly connected to the pull-up node, and another thin- film transistor including a second active layer including an oxide semiconductor material different from a oxide semiconductor material of the first active layer, and directly connected to the pull-up node.