Oxide Semiconductor Dual-Gate Transistor for Display Driver Integration
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Solution Overview
Problem
The manufacturing cost of display devices increases with the number of gate lines and signal lines, making it difficult to integrate IC chips for driving, and existing thin film transistors using amorphous or polycrystalline silicon have limitations in terms of mobility and scalability.
Innovation Solution
A thin film transistor using an oxide semiconductor with a dual-gate structure, where the oxide semiconductor layer is interposed between two gate electrodes, allowing for high dynamic characteristics and reduced parasitic capacitance, and the use of low-resistance oxide semiconductor layers as source and drain regions to enhance on-state current and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the number of gate lines and signal lines is increased to increase display region size and definition, then the display quality is improved, but the manufacturing cost increases and IC chip mounting becomes difficult
Solution Approach 1:
The patent integrates the driver circuit directly into the display device substrate, merging the previously separate IC chip functionality with the display panel. This eliminates the need for external IC chip mounting and reduces manufacturing complexity despite increased display region size and line count.
Solution Approach 2:
The display device substrate serves multiple functions: it acts as both the display region substrate and the mounting substrate for driver circuits. The same substrate that displays images also hosts the integrated circuit elements for signal generation and control, reducing the need for separate dedicated substrates.
2Area of stationary object
If a thin film transistor using amorphous silicon is used, then the transistor can be formed over a larger glass substrate area, but the electric field effect mobility is low
Solution Approach 1:
The patent employs different semiconductor materials in different regions of the display device. Amorphous silicon is used in regions where large area coverage is needed, while other materials or structures are used where high mobility is critical. This local differentiation optimizes both area coverage and performance.
Solution Approach 2:
The patent uses composite structures combining amorphous silicon with other materials or configurations. The thin film transistor structure incorporates multiple layers and materials that work together to enhance the effective mobility of amorphous silicon-based devices while maintaining the ability to form over large substrate areas.
3Reliability
If a thin film transistor using polycrystalline silicon is used, then the electric field effect mobility is high, but a crystallization process such as laser annealing is necessary and it is not suitable for larger glass substrates
Solution Approach 1:
The patent accepts certain process simplifications and uses materials that can be deposited using simpler, more scalable techniques suitable for large substrates. Rather than requiring complex laser annealing processes, the design uses materials and structures that achieve adequate performance through more straightforward manufacturing methods.
Solution Approach 2:
The patent modifies transistor design parameters such as channel width, length, and doping concentrations to compensate for the lower mobility of amorphous silicon or simpler semiconductor materials. By adjusting these parameters, the device achieves the required performance without requiring high-temperature crystallization processes.
4Productivity
If the thin film transistor is required to have high dynamic characteristics for driver circuit operation, then the on-state current and frequency characteristics must be improved, but this increases manufacturing complexity
Solution Approach 1:
The transistor structure is divided into distinct functional regions with specific doping profiles and material compositions. By segmenting the device into regions optimized for different functions (channel formation, carrier injection, isolation), the patent achieves high dynamic characteristics while maintaining manufacturing feasibility through standardized process steps.
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 configuration reduces manufacturing costs by enabling high-speed driving and low power consumption while maintaining high on-state current and reliability, allowing for larger display regions without significant increases in manufacturing complexity.
Implementation Method 1
The oxide semiconductor film can be formed by a sputtering 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. Therefore, when the pixel portion and the driver circuit are provided over the same substrate, manufacturing cost can be reduced.