TFT Substrate Insulating Layer Etching and Tapered Opening Design
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Solution Overview
Problem
Conventional techniques face challenges in manufacturing a thin film transistor (TFT) substrate with desired properties, particularly in reducing throughput during wet etching of aluminum oxide films and preventing electrode breakage at the edge of openings in the insulating layer.
Innovation Solution
A method involving a TFT substrate manufacturing process where an insulating layer with a three-layer structure, including a silicon oxide film, an aluminum oxide film, and a silicon oxide film, is formed, with a resist pattern above the silicon oxide film, processed by dry etching, and the aluminum oxide film processed by wet etching using an alkaline solution to maintain the desired shape and reduce throughput issues, and the opening is formed with a downward tapered shape to minimize electrode breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wet etching is used to process the aluminum oxide film, then the etching can be performed effectively, but throughput decreases during the etching process
Solution Approach 1:
The insulating layer is divided into three separate films (first film, second aluminum oxide film, third film) that are processed in sequence. This segmentation allows the aluminum oxide film to be etched separately using wet etching while other layers are processed using dry etching, thereby maintaining overall throughput by parallelizing processing steps and avoiding bottlenecks caused by slow wet etching of the entire insulating layer.
Solution Approach 2:
Different etching methods are applied to different parts of the insulating layer structure. The aluminum oxide film (second film) is processed by wet etching to achieve effective removal, while the first and third films are processed by dry etching to maintain throughput. This local differentiation of processing quality allows each material to be etched by the most suitable method without compromising overall productivity.
2Ease of manufacture
If a vertical opening shape is formed, then the fabrication is simpler, but electrode breakage occurs at the edge of the opening
Solution Approach 1:
The opening shape is changed from a vertical cylindrical form to a tapered form where the cross-sectional area varies along the depth. Specifically, the opening has a larger cross-sectional area at the upper surface than at the lower surface, creating an asymmetric geometry that reduces stress concentration at the electrode edges while maintaining fabrication feasibility through controlled etching processes.
Solution Approach 2:
The opening edges are designed with curved surfaces rather than sharp corners. The tapered shape creates smooth transitions and rounded profiles at the opening edges, which eliminates stress concentration points that would otherwise cause electrode breakage. This curvature modification maintains electrode integrity while preserving the overall simple fabrication approach.
3Device complexity
If a single-layer insulating structure is used, then the device complexity is reduced, but the desired properties cannot be achieved
Solution Approach 1:
The insulating layer is constructed as a composite structure with three different films, each having distinct material properties. The first film, second aluminum oxide film, and third film are combined to achieve specific electrical, mechanical, and etching characteristics that a single material could not provide. This composite approach enables precise control over TFT substrate properties including insulation performance, stress management, and etching selectivity.
Solution Approach 2:
The insulating layer is segmented into three functional films that can be independently optimized and processed. Each film serves a specific purpose: the first film provides base insulation, the second aluminum oxide film offers barrier properties and controlled etching characteristics, and the third film completes the insulating function while enabling precise opening formation. This segmentation allows achievement of desired substrate properties through tailored material selection and processing for each layer.
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
This approach enables the production of a TFT substrate with desired properties by reducing throughput losses during wet etching and minimizing electrode breakage at the opening edges, thus enhancing the manufacturing efficiency and reliability of the TFT substrate.
Implementation Method 1
processing the third film by dry etching
Implementation Method 2
processing the second film by wet etching
Data Source
AI summary
A method of manufacturing a thin film transistor (TFT) substrate in which a TFT including an oxide semiconductor layer is formed, the method including: forming an insulating layer to cover the oxide semiconductor layer; and forming an opening in the insulating layer, wherein the insulating layer includes a first film, a second film which is provided above the first film and is an aluminum oxide film, and a third film which is provided above the second film and is a film including silicon, and the forming of an opening includes: forming a resist pattern above the third film; processing the third film by dry etching; and processing the second film by wet etching.