Amorphous IGZO Thin Film Transistor Substrate for High Mobility and Aperture Ratio
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Solution Overview
Problem
The manufacturing cost of thin film transistor substrates for liquid crystal displays is high due to the use of amorphous silicon with low carrier mobility and crystalline silicon, which also presents uniformity issues, and existing methods require multiple masks and can result in undercut defects affecting the aperture ratio.
Innovation Solution
A thin film transistor substrate design using a semiconductor pattern and pixel electrode made from amorphous indium-gallium-zinc-oxide, where the semiconductor pattern and pixel electrode are in the same layer, with a common electrode having different electrical properties, and an etch stopper is used to prevent damage and reduce the number of masks required, allowing for reduced manufacturing costs and improved aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous silicon is used for the active layer, then the manufacturing process is simpler, but the carrier mobility is low
Solution Approach 1:
The patent changes the material parameter from conventional amorphous silicon to amorphous indium-gallium-zinc-oxide (a-IGZO), which fundamentally alters the electrical properties while maintaining the amorphous deposition process. This material substitution achieves high carrier mobility (exceeding 10 cm²/Vs) comparable to crystalline silicon, while preserving the simplicity of low-temperature sputtering fabrication
Solution Approach 2:
The patent employs a composite material approach by combining indium, gallium, and zinc oxides in specific ratios to create a-IGZO. This composite oxide semiconductor material integrates the advantages of different metal oxides to achieve optimal electrical properties, including high carrier mobility and uniform characteristics, while remaining compatible with existing thin-film transistor manufacturing processes
2Reliability
If crystalline silicon is used for the active layer, then the carrier mobility is high, but it is difficult to secure uniform properties
Solution Approach 1:
The patent transitions from crystalline silicon to amorphous indium-gallium-zinc-oxide, changing both the material composition and structural state. The amorphous structure of a-IGZO eliminates grain boundary issues inherent in crystalline materials, providing uniform electrical properties across the film while achieving high carrier mobility through controlled stoichiometry and low-temperature processing
Solution Approach 2:
The patent achieves homogeneity by using sputtering deposition to create a uniform amorphous oxide semiconductor film. The amorphous structure inherently provides compositional uniformity without grain boundaries, and the controlled sputtering process ensures consistent material properties across the entire substrate, eliminating the variability associated with crystalline silicon fabrication
3Manufacturing precision
If multiple masks are used in the manufacturing process, then the patterning precision is improved, but the manufacturing cost increases
Solution Approach 1:
The patent merges the formation of the semiconductor pattern and pixel electrode into a single sputtering step using a patterned mask. This consolidation reduces the total number of masking operations from multiple separate steps to one integrated step, thereby lowering manufacturing costs while maintaining the required patterning precision through careful mask design and single-step deposition 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 reduces manufacturing costs by simplifying the process, preventing undercut defects, and enhancing the aperture ratio of pixels, while maintaining high carrier mobility and uniform properties.
Implementation Method 1
The pixel electrode may be formed by irradiating an ultraviolet ray onto the semiconductor pattern through a rear surface of the substrate using the gate electrode as a mask.
Data Source
AI summary
A thin film transistor substrate includes a substrate; a gate electrode on the substrate; a semiconductor pattern on the gate electrode; a source electrode on the semiconductor pattern; a drain electrode on the semiconductor pattern and spaced apart from the source electrode; a pixel electrode connected to the drain electrode; and a common electrode partially overlapped with the pixel electrode. The semiconductor pattern is in a same layer of the thin film transistor substrate as the pixel electrode and has an electrical property different from an electrical property of the pixel electrode.