Dual-Gate Oxide Semiconductor Transistors for Display Driver Integration
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Solution Overview
Problem
The manufacturing cost of display devices increases due to the complexity of integrating IC chips for gate and signal lines, especially as display size and pixel density rise, and existing thin film transistors using amorphous or polycrystalline silicon have limitations in field effect mobility and scalability.
Innovation Solution
A semiconductor device utilizing an oxide semiconductor with a dual-gate structure, where the oxide semiconductor layer is positioned between source and drain electrodes and overlapped by both gate electrodes, enhancing field effect mobility and allowing for high dynamic characteristics, thus reducing manufacturing costs and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If amorphous silicon is used for thin film transistor, then the transistor can be formed over a glass substrate with a larger area, but the field effect mobility is low
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to oxide semiconductor, which fundamentally alters the electrical properties and enables high field effect mobility while maintaining compatibility with large-area glass substrates
Solution Approach 2:
The patent employs a composite structure combining oxide semiconductor layer with metal gates and insulating layers, creating a thin film transistor that achieves both large-area fabrication capability and high mobility performance
2Speed
If polycrystalline silicon is used for thin film transistor, then the field effect mobility is high, but a crystallization step such as laser annealing is necessary and such a transistor is not always suitable for a larger glass substrate
Solution Approach 1:
The patent changes the material from polycrystalline silicon to oxide semiconductor, eliminating the need for crystallization steps like laser annealing while maintaining high field effect mobility, thereby simplifying the manufacturing process for large-area substrates
Solution Approach 2:
The oxide semiconductor approach replaces expensive and complex laser annealing processes with simpler, more cost-effective deposition and annealing methods that are suitable for large-area production
3Area of stationary object
If the size of a display region is increased, then the number of pixels is increased, but the number of gate lines and signal lines is increased making it difficult to mount an IC chip
Solution Approach 1:
The patent merges the driver circuit functionality directly into the display substrate by fabricating thin film transistors alongside the pixel circuits, eliminating the need for separate IC chip mounting and reducing overall system complexity
Solution Approach 2:
The oxide semiconductor thin film transistors serve multiple functions: they act as switching elements in pixel circuits and as driver circuit elements, providing universal high-performance transistor functionality across the entire display device
4Ease of manufacture
If a thin film transistor using an oxide semiconductor is employed in a driver circuit, then manufacturing cost is reduced, but high dynamic characteristics are required
Solution Approach 1:
The patent changes the transistor material to oxide semiconductor, which inherently provides high field effect mobility and excellent on/off characteristics, meeting the high dynamic performance requirements for driver circuits while enabling cost-effective manufacturing
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 dual-gate oxide semiconductor structure enables high-speed operation and low power consumption, reduces parasitic capacitance, and improves the reliability of thin film transistors, allowing for larger display formats without significant increases in manufacturing complexity or cost.
Implementation Method 1
The oxide semiconductor film can be formed by a puttering method or the like at a temperature of 300° C. or lower
Data Source
AI summary
As a display device has a higher definition, the number of pixels, gate lines, and signal lines are increased. When the number of the gate lines and the signal lines are increased, there occurs a problem that it is difficult to mount an IC chip including a driver circuit for driving the gate and signal lines by bonding or the like, whereby manufacturing cost is increased. A pixel portion and a driver circuit for driving the pixel portion are provided over the same substrate, and at least part of the driver circuit includes a thin film transistor using an oxide semiconductor interposed between gate electrodes provided above and below the oxide semiconductor. The pixel portion and the driver portion are provided over the same substrate, whereby manufacturing cost can be reduced.