Oxide TFT Circuit Board Structure for Precise Through-Hole Etching
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Solution Overview
Problem
The formation of through-holes in TFTs with oxide semiconductors and AlO barrier films is challenging due to different etch conditions for various materials, leading to difficulties in controlling the depth of through-holes and potential penetration of etching beyond the intended layers, which can render the TFT inoperable.
Innovation Solution
A TFT circuit board structure is implemented, where a first interlayer insulating film, a cured film, and an AlO film are used to cover the oxide semiconductor, with through-holes formed in these layers to connect the drain, source, and gate electrodes to wires, utilizing a two-stage dry etching process to precisely control the etching depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a through-hole is formed in multiple steps to connect source or drain to signal wire or pixel electrode, then electrical connection is achieved, but it becomes difficult to control the depth of the through-hole and may penetrate the drain or source formed of oxide semiconductor
Solution Approach 1:
The patent divides the protective film structure into multiple distinct layers (first protective film, second protective film, and AlO barrier film) with different etch selectivities. This segmentation allows the through-hole formation process to be divided into stages, where each layer is etched at a different rate, enabling precise depth control and preventing penetration into the oxide semiconductor electrodes.
Solution Approach 2:
The patent introduces an AlO barrier film as an intermediary layer between the protective films and the oxide semiconductor. This intermediary layer has distinct etch characteristics that allow it to serve as a stop layer during etching, preventing the etch process from penetrating into the underlying oxide semiconductor electrodes while still allowing electrical connection through controlled through-holes.
2Reliability
If AlO is used as a blocking film for moisture and hydrogen, then the properties of oxide semiconductor are protected, but different etch conditions are required for AlO, SiO, SiN, and other materials making through-hole formation complex
Solution Approach 1:
The patent applies different material properties to different layers of the protective film structure. The first protective film (SiO or SiN) and second protective film have different etch selectivities, allowing localized differentiation in etching behavior. This enables the etching process to selectively remove each layer at different rates, simplifying the overall process while maintaining protection of the oxide semiconductor.
Solution Approach 2:
The patent utilizes changes in etch selectivity parameters across different film layers. By selecting materials with distinct etch characteristics (SiO, SiN, and AlO), the process can control etching depth and rate by adjusting etch conditions, thereby managing complexity while achieving precise through-hole formation without penetrating the oxide semiconductor.
3Reliability
If through-hole is formed to penetrate the capping metal due to over-etching, then electrical connection is established, but the contact resistance at the connecting point becomes unstable
Solution Approach 1:
The patent structures the protective film with multiple layers having different etch selectivities, creating a cushioning effect that prevents over-etching. The etch process naturally stops at each layer interface due to the selectivity differences, providing a built-in stop mechanism that prevents penetration into the oxide semiconductor electrodes and ensures stable contact resistance.
Solution Approach 2:
The patent creates a feedback mechanism through the etch selectivity differences between layers. As the etching process progresses, the rate of removal changes at each layer interface, providing inherent feedback that controls etching depth. This self-regulating process prevents over-etching and ensures precise through-hole formation with stable electrical connections.
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 structure allows for precise control of the depth of through-holes, preventing over-etching and ensuring stable electrical connections, thereby maintaining the operational integrity of the TFT.
Implementation Method 1
utilizing a two-stage dry etching process to precisely control the etching depth
Data Source
AI summary
The invention allows stable fabrication of a TFT circuit board used in a display device and having thereon an oxide semiconductor TFT. A TFT circuit board includes a TFT that includes an oxide semiconductor. The TFT has a gate insulating film formed on part of the oxide semiconductor and a gate electrode formed on the gate insulating film. A portion of the oxide semiconductor that is covered with the gate electrode 104 and a portion of the oxide semiconductor that is not covered with the gate electrode are both covered with a first interlayer insulating film. The first interlayer insulating film is covered with a first film 106, and the first film is covered with a first AlO film.