Multi-Layer Scan Circuit Using Substrate Bias to Reduce Leakage
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Solution Overview
Problem
Related scan circuits using polysilicon transistors suffer from leakage current issues, and the substrate bias effect is not effectively utilized to improve transistor performance.
Innovation Solution
The use of metal oxide transistors with substrate bias effect to ensure correct on/off operation by setting the substrate voltage to a positive value, which shifts the transistor's threshold voltage towards positive bias, and the integration of a scan circuit with transistors having gate electrodes in different layers and connected to a unified power supply signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polysilicon transistors are used in scan circuits, then the circuit can be manufactured with conventional processes, but leakage current increases and transistor performance deteriorates
Solution Approach 1:
The patent changes the material parameter from polysilicon to metal oxide semiconductor, fundamentally altering the electrical characteristics to reduce leakage current. This material substitution enables the transistor to operate with significantly lower leakage while maintaining compatibility with existing manufacturing processes through appropriate deposition and treatment techniques.
Solution Approach 2:
The patent employs a composite structure combining metal oxide semiconductor material with specific gate electrode configurations (multi-layer gate structures with different materials). This composite approach leverages the advantageous properties of different materials to achieve both low leakage current and manufacturability in display panel fabrication.
2Device complexity
If substrate bias effect is not utilized, then the transistor structure remains simple, but leakage current cannot be effectively reduced
Solution Approach 1:
The patent introduces a substrate bias mechanism as an intermediary control method. By applying a positive voltage to the substrate relative to the source, the electric field distribution within the transistor channel is modified, creating a depletion region that suppresses leakage current without requiring complex structural modifications to the transistor itself.
Solution Approach 2:
The substrate bias effect utilizes voltage parameter changes (applying positive substrate voltage) to dynamically control the transistor's threshold voltage and leakage characteristics. This electrical parameter adjustment provides an effective means to reduce leakage current while maintaining a relatively simple physical structure.
3Device complexity
If gate electrodes are not differentiated by layer, then the manufacturing process is simpler, but power supply control precision deteriorates
Solution Approach 1:
The patent segments the gate electrode into multiple layers (first gate electrode and second gate electrode) that can be independently controlled. This segmentation allows different power supply signals to be applied to different gate layers, enabling precise control over the transistor's switching characteristics and threshold voltage without requiring overly complex single-layer gate structures.
Solution Approach 2:
The patent transitions from a single-layer gate electrode to a multi-layer gate structure, adding a vertical dimension to the gate control architecture. This dimensional change enables independent electrical control of each gate layer, improving power supply signal control precision while maintaining manufacturing feasibility through sequential deposition processes.
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
This approach reduces leakage current and ensures accurate transistor operation within the correct voltage range, avoiding errors and improving the performance of scan circuits.
Implementation Method 1
the substrate bias effect is not effectively utilized to improve transistor performance... by setting the substrate voltage to a positive value, which shifts the transistor's threshold voltage towards positive bias
Data Source
AI summary
A scan circuit is provided. The scan circuit includes a plurality of scan units. A respective scan unit of the plurality of scan units includes a plurality of transistors. A respective gate electrode of a respective transistor of the plurality of transistors includes a first portion and a second portion in different layers. First portions of respective gate electrodes of the plurality of transistors in the respective scan unit are configured to be provided with a power supply signal. Second portions of the respective gate electrodes of the plurality of transistors in the respective scan unit are configured to be provided with gate scanning signals, respectively. First portions of gate electrodes of at least two transistors in the respective scan unit are parts of a unitary structure.