Amorphous Oxide Transistor for Flexible Displays
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Solution Overview
Problem
Conventional amorphous oxide semiconductors used in transistors for displays have difficulty achieving a stable amorphous phase, leading to low electron mobility and high electron carrier concentrations, which hinder the production of transistors with desired properties such as low off-current and high on-off ratios, especially when integrated on flexible resin substrates.
Innovation Solution
The development of an amorphous oxide semiconductor with an electron carrier concentration of less than 10^18/cm^3, achieved by controlling the oxygen atmosphere during film formation, specifically using InGaZnO materials, which allows for increased electron mobility and stable amorphous phase formation, enabling the production of transistors suitable for flexible displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional amorphous oxide semiconductor is used, then the transistor can be formed on resin substrate at low temperature, but the electron mobility is low and electron carrier concentration is high
Solution Approach 1:
The patent changes the chemical composition parameters of the oxide semiconductor by incorporating In, Ga, and Zn in specific ratios. This compositional parameter change enables simultaneous achievement of low-temperature processability and high electron mobility, resolving the contradiction between temperature constraint and performance requirement
Solution Approach 2:
The patent uses composite oxide semiconductor material containing multiple elements (In-Ga-Zn-O system) rather than simple oxide. This composite material structure allows combining the benefits of different elements: In for high mobility, Ga for stability, and Zn for low-temperature processing compatibility
2Ease of manufacture
If conventional amorphous oxide semiconductor is used, then the transistor can be formed on resin substrate, but the off-current is large and on-off ratio is low
Solution Approach 1:
The patent optimizes the electron carrier concentration parameter by controlling the stoichiometric composition of In-Ga-Zn-O and oxygen content. This parameter control reduces off-current while maintaining the ability to form on resin substrates, resolving the contradiction between ease of manufacture and device performance
3Ease of manufacture
If polycrystalline ZnO is used, then the material can be formed, but carrier scattering occurs at grain boundaries and electron mobility cannot be increased
Solution Approach 1:
The patent changes the structural parameter from polycrystalline to amorphous phase by controlling deposition conditions and composition. The amorphous structure eliminates grain boundaries that cause carrier scattering, thereby achieving high electron mobility while maintaining ease of formation
Solution Approach 2:
The patent creates a uniform amorphous phase throughout the film without localized crystalline regions. This local quality uniformity prevents carrier scattering at grain boundaries and ensures consistent high electron mobility across the entire transistor channel
4Illumination intensity
If oxide with electron carrier concentration of 10^18/cm^3 or more is used, then the material is suitable for transparent electrode, but sufficient on-off ratio cannot be secured
Solution Approach 1:
The patent precisely controls the electron carrier concentration parameter within the range of 10^16 to 10^18/cm^3, which is lower than conventional transparent electrodes. This parameter optimization maintains sufficient transparency while enabling adequate on-off ratio for transistor operation
Data Source
AI summary
An active matrix display comprising a light control device and a field effect transistor for driving the light control device. The active layer of the field effect transistor comprises an amorphous.