Oxide TFT Light-Emitting Structure for Stable Driver Switching
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Solution Overview
Problem
Thin film transistors with oxide semiconductor films face challenges in achieving high operation speed and stable electric characteristics, particularly in driver circuits, where low channel length and high channel width lead to reduced switching characteristics and increased capacity load, while also requiring reduced variation in electrical characteristics.
Innovation Solution
A light-emitting device structure incorporating a transistor with a gate electrode, gate insulating layer, oxide semiconductor layer, source and drain electrode layers, and an oxide insulating layer, where the transistor for the driver circuit has a conductive layer overlapping with the gate and semiconductor layers to control threshold voltage, and the pixel transistor is connected to a color filter layer and EL layer for stable operation, using a manufacturing method that includes dehydration or dehydrogenation of the oxide semiconductor layer to reduce impurities and improve reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the channel length of the thin film transistor is reduced to increase operation speed, then the operation speed is improved, but the switching characteristic (on-off ratio) is lowered
Solution Approach 1:
The patent applies parameter changes by modifying the physical and chemical properties of the oxide semiconductor layer through controlled dehydration and dehydrogenation processes. By adjusting the purity and crystalline structure of the oxide semiconductor, the transistor achieves high operation speed with maintained switching characteristics, resolving the contradiction between speed and reliability.
2Speed
If the channel width of the thin film transistor is increased to improve operation speed, then the operation speed is improved, but the capacity load of the transistor is increased
Solution Approach 1:
The patent changes the material parameters of the oxide semiconductor layer to achieve higher carrier mobility and improved electrical characteristics. This allows the transistor to operate at high speeds with reduced capacitance, effectively resolving the contradiction between operation speed and capacity load.
3Reliability
If dehydration or dehydrogenation treatment is applied to the oxide semiconductor layer to improve reliability, then the electrical characteristics are stabilized, but the manufacturing process complexity is increased
Solution Approach 1:
The patent applies preliminary action by performing dehydration and dehydrogenation treatments on the oxide semiconductor layer before forming the transistor structure. This preliminary purification step removes water and hydrogen from the oxide semiconductor, stabilizing its electrical characteristics and reducing variability, which simplifies subsequent manufacturing steps and improves overall device reliability.
4Reliability
If a conductive layer is added over the oxide semiconductor layer to control threshold voltage, then the electrical characteristics are improved, but the device structure complexity is increased
Solution Approach 1:
The conductive layer serves multiple functions: it acts as an electrode for applying voltage to the oxide semiconductor layer, functions as a gate for controlling threshold voltage, and provides electrical connection to other circuit elements. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while achieving improved threshold voltage control.
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 solution enables high-speed operation with stable electric characteristics and reduced variation in electrical characteristics, enhancing the reliability and performance of thin film transistors in both driver and pixel circuits, facilitating the production of reliable light-emitting devices with improved switching and display performance.
Implementation Method 1
dehydration or dehydrogenation of the oxide semiconductor layer to reduce impurities
Implementation Method 2
dehydration or dehydrogenation of the oxide semiconductor layer to reduce impurities
Implementation Method 3
a conductive layer over the oxide insulating layer, which overlaps with the gate electrode layer and the oxide semiconductor layer
Implementation Method 4
an oxide insulating layer, which is in contact with part of the oxide semiconductor layer, over the oxide semiconductor layer, the source electrode layer, and the drain electrode layer
Data Source
AI summary
An object is to improve reliability of a light-emitting device. A light-emitting device has a driver circuit portion including a transistor for a driver circuit and a pixel portion including a transistor for a pixel over one substrate. The transistor for the driver circuit and the transistor for the pixel are inverted staggered transistors each including an oxide semiconductor layer in contact with part of an oxide insulating layer. In the pixel portion, a color filter layer and a light-emitting element are provided over the oxide insulating layer. In the transistor for the driver circuit, a conductive layer overlapping with a gate electrode layer and the oxide semiconductor layer is provided over the oxide insulating layer. The gate electrode layer, a source electrode layer, and a drain electrode layer are formed using metal conductive films.