Oxide Semiconductor TFT Driver Integration for High-Density Displays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing thin film transistors using amorphous silicon have low electric field effect mobility, while those using crystalline silicon require costly laser annealing and are not suitable for large glass substrates, and increasing pixel density in display devices complicates mounting IC chips for driver circuits, increasing manufacturing costs.
Innovation Solution
Employing a thin film transistor with an oxide semiconductor layer interposed between two gate electrodes, which can be formed at low temperatures and provides high dynamic characteristics, allowing for high-speed operation and reduced manufacturing costs by integrating driver circuits on the same substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a thin film transistor is formed using amorphous silicon, then it can be formed over a glass substrate with a larger area, but the electric field effect mobility is low
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to oxide semiconductor, which maintains the ability to be formed over large area substrates while significantly improving electric field effect mobility. The oxide semiconductor layer is deposited using sputtering at temperatures of 300°C or lower, preserving the large substrate area capability while achieving higher mobility through material composition change.
Solution Approach 2:
The patent employs a composite structure with an oxide semiconductor layer as the active channel material, combining the advantages of amorphous silicon (easy formation over large areas) with the high mobility characteristics of crystalline materials. The oxide semiconductor is formed over a gate electrode and gate insulating layer, creating a composite transistor structure that achieves both large area compatibility and high mobility.
2Reliability
If a thin film transistor is formed using crystalline silicon, then the electric field effect mobility is high, but a crystallization process 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 crystalline silicon to oxide semiconductor, eliminating the need for high-temperature laser annealing processes. The oxide semiconductor can be deposited at 300°C or lower using sputtering, making it suitable for large glass substrates while maintaining high electric field effect mobility through the inherent properties of the oxide semiconductor material.
Solution Approach 2:
The patent replaces the expensive and complex laser annealing process with a simpler, lower-cost sputtering deposition process. The oxide semiconductor layer can be formed directly in an amorphous or microcrystalline state without requiring subsequent high-temperature crystallization steps, reducing manufacturing complexity and cost while maintaining high mobility.
3Productivity
If the size of a display region is increased and pixel density is increased, then the number of pixels and gate lines increases, but it becomes difficult to mount IC chips including driver circuits by bonding, whereby manufacturing cost is increased
Solution Approach 1:
The patent merges the driver circuit functionality directly into the display device by forming thin film transistors using oxide semiconductors on the same substrate as the display pixels. This integration eliminates the need for separate IC chip mounting and bonding processes, reducing manufacturing complexity and cost while supporting high pixel density and increased display region size.
Solution Approach 2:
The oxide semiconductor thin film transistor serves multiple functions: it acts as the switching element for display pixels and simultaneously serves as the driver circuit transistors. This multi-functional approach allows the same material and process to be used throughout the device, simplifying manufacturing and reducing costs associated with integrating separate driver IC chips.
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 structure with an oxide semiconductor layer between gate electrodes enhances transistor reliability and reduces manufacturing costs by enabling high-speed, low-power consumption operation of driver circuits without increasing process 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, a problem of higher manufacturing cost, because it is difficult to mount an IC chip including a driver circuit for driving of the gate and signal lines by bonding or the like. 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 portion are provided over the same substrate, manufacturing cost can be reduced.