Oxide Semiconductor Dual-Gate Transistor for Display Pixel Stability
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Solution Overview
Problem
Display devices using light-emitting elements face issues with fluctuations in threshold voltage of driver transistors, which affect image quality, and require transistors with high field-effect mobility for high-speed driving and low power consumption.
Innovation Solution
The use of oxide semiconductor films with specific channel lengths and dual-gate transistor structures for driver and selection transistors, where the channel length of driver transistors is between 0.5 μm and 4.5 μm, and selection transistors have longer channel lengths, along with overlapping gate electrodes to enhance field-effect mobility and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the channel length of the driver transistor is reduced to improve field-effect mobility and on-state current, then high-speed driving is achieved, but the threshold voltage becomes more sensitive to degradation and fluctuations
Solution Approach 1:
The patent introduces a dual-gate transistor structure where a second gate electrode is added below the oxide semiconductor film, creating a vertical dimension for gate control. This allows independent control of the channel from both top and bottom, enabling high field-effect mobility through enhanced electric field while maintaining threshold voltage stability through balanced gate control. The channel length is simultaneously optimized to be between 0.5 μm and 4.5 μm to achieve high-speed performance without excessive threshold voltage degradation.
Solution Approach 2:
The patent optimizes the channel length parameter to a specific range (0.5 μm to 4.5 μm) that balances high-speed performance and threshold voltage stability. Additionally, the oxide semiconductor film thickness is controlled at 3 nm to 200 nm, and the gate electrode dimensions are precisely defined (first gate: 0.5 μm to 5 μm width, 0.1 μm to 5 μm length; second gate: 0.5 μm to 10 μm width, 0.1 μm to 10 μm length) to achieve optimal electrical characteristics that simultaneously improve mobility and stabilize threshold voltage.
2Speed
If oxide semiconductor films are used to achieve high field-effect mobility for high-speed driving, then driving speed is improved, but power consumption increases due to higher on-state current
Solution Approach 1:
The dual-gate transistor structure enables dynamic control of the channel conductivity through independent gating from both top and bottom. By applying appropriate voltages to the first and second gate electrodes, the channel can be precisely controlled to achieve high on-state current for fast switching while minimizing off-state leakage current, thus optimizing the balance between driving speed and power consumption.
Solution Approach 2:
The patent optimizes multiple parameters including oxide semiconductor film thickness (3 nm to 200 nm), channel length (0.5 μm to 4.5 μm), and gate electrode dimensions to achieve optimal electrical characteristics. These parameter optimizations enable the transistor to achieve high field-effect mobility for fast switching while controlling the on-state current to manage power consumption effectively.
3Use of energy by moving object
If the channel length of the selection transistor is increased to reduce power consumption, then cutoff current is reduced, but the aperture ratio decreases and device area increases
Solution Approach 1:
The patent applies different channel length optimizations to different transistor types within the same device. The driver transistor uses a shorter channel length (0.5 μm to 4.5 μm) for high-speed performance, while the selection transistor uses a longer channel length for low power consumption. This localized optimization allows each transistor to be tailored for its specific function without compromising overall device performance or excessive area increase.
Data Source
AI summary
In a pixel including a selection transistor, a driver transistor, and a light-emitting element, as the driver transistor, a transistor is used in which a channel is formed in an oxide semiconductor film and its channel length is 0.5 μm or greater and 4.5 μm or less. The driver transistor includes a first gate electrode over an oxide semiconductor film and a second gate electrode below the oxide semiconductor film. The first gate electrode and the second gate electrode are electrically connected to each other and overlap with the oxide semiconductor film. Furthermore, in the selection transistor of a pixel, which does not need to have field-effect mobility as high as that of the driver transistor, a channel length is made longer than at least the channel length of the driver transistor.