Crystalline Oxide Semiconductor Thin Film for High-Resolution Displays
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Solution Overview
Problem
Current oxide semiconductor thin films for TFTs have high carrier density and instability due to oxygen defects, which affects their performance and reliability, especially in high-resolution liquid crystal displays requiring high-speed driving.
Innovation Solution
A sputtering target with a specific composition of indium, gallium, and zinc oxides, where the Ga/(In+Ga) ratio is 0.08-0.20 and the Zn/(In+Ga+Zn) ratio is 0.0001-0.08, forming a crystalline oxide semiconductor thin film with a bixbyite structure, reducing carrier density and enhancing carrier mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If transparent amorphous oxide thin film is deposited by vapor deposition, then transparency is achieved, but carrier density becomes high and stability decreases due to oxygen defects
Solution Approach 1:
The patent applies phase transition by transforming the oxide thin film from amorphous phase to crystalline phase (specifically bixbyite structure). This phase transition eliminates oxygen defects inherent in amorphous structures, thereby reducing carrier density and improving stability while maintaining transparency. The crystalline structure provides stable lattice positions that prevent oxygen vacancy formation.
Solution Approach 2:
The patent uses composite material strategy by combining multiple metal elements (In, Ga, Zn) in specific ratios to form an In-Ga-Zn-O crystalline oxide. This composite composition creates a stable bixbyite structure where the synergistic effect of different metal elements reduces oxygen defects and stabilizes the crystal lattice, thereby improving device reliability while maintaining optical transparency.
2Reliability
If carrier density is reduced in oxide semiconductor thin film, then on/off ratio of TFTs improves, but manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent applies parameter changes by precisely controlling the atomic ratios of metal elements (Ga/(In+Ga) = 0.08-0.20, Zn/(In+Ga+Zn) = 0.0001-0.08) to achieve the desired carrier density reduction. By optimizing these compositional parameters, the patent successfully reduces carrier density to 8.0×10^17 cm^-3 or less while maintaining manufacturability through well-defined composition ranges.
Solution Approach 2:
The patent applies local quality by creating specific compositional regions within the oxide thin film structure. The controlled distribution of Ga and Zn atoms in the bixbyite lattice creates localized electronic environments that reduce carrier density while maintaining overall film uniformity. This local compositional control enables precise manipulation of electrical properties without compromising manufacturing feasibility.
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 results in a thin film with a carrier density of 8.0×10^17 cm^-3 or less and a carrier mobility of 10 cm^2/V·s or more, improving the on/off ratio of TFTs and stability, making it suitable for high-resolution liquid crystal displays.
Implementation Method 1
a sputtering target that achieves reduced carrier density of a crystalline oxide semiconductor thin film when the sputtering target contains zinc
Implementation Method 2
a zinc-containing oxide sintered body most suitable for obtaining the sputtering target
Data Source
AI summary
An oxide sintered body which, when made into an oxide semiconductor thin film by sputtering, can achieve low carrier density and high carrier mobility, and a sputtering target using said oxide sintered body are provided. This oxide sintered body contains indium, gallium and zinc as oxides. The gallium content is 0.08 or more and less than 0.20 in terms of Ga/(In+Ga) atomic ratio, and the zinc content is 0.0001 or more and less than 0.08 in terms of Zn/(In+Ga+Zn) atomic ratio. This crystalline oxide semiconductor thin film is formed with the oxide sintered body as a sputtering target, and can achieve a carrier density of 8.0×1017 cm−3 or less and a carrier mobility of 10 cm2/V·s or greater.