Oxide Semiconductor TFT Circuit Board With AlO Etch-Stop Through-Holes
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Solution Overview
Problem
The formation of through-holes in oxide semiconductor thin-film transistors (TFTs) using aluminum oxide (AlO) barrier films is challenging due to varying etch conditions, leading to instability and potential penetration of the drain or source electrodes, which can render the TFT inoperable.
Innovation Solution
A TFT circuit structure is implemented with a cured film acting as an etching stopper under the AlO film, allowing precise control of through-hole formation using two-stage dry etching, preventing over-etching and ensuring stable connections between electrodes and wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AlO barrier film is used to protect oxide semiconductor from moisture, then moisture barrier properties are improved, but through-hole formation becomes difficult due to varying etch conditions
Solution Approach 1:
A cured film is introduced as an intermediary layer between the AlO barrier film and the etching process. This cured film acts as an etching stopper that is easier to etch than AlO, allowing through-holes to be formed without directly etching the AlO film. The cured film mediates between the moisture barrier requirement (AlO film integrity) and the through-hole formation requirement (etchability).
Solution Approach 2:
The barrier film structure is segmented into multiple layers: the AlO barrier film for moisture protection and a separate cured film for etching stopper functionality. This segmentation allows each layer to perform its specific function optimally - AlO provides moisture barrier while the cured film facilitates through-hole formation with controlled etching.
2Adaptability or versatility
If through-holes are formed in multiple steps to connect source/drain to signal wires, then connectivity is improved, but depth control becomes difficult and electrode penetration risk increases
Solution Approach 1:
The cured film serves as an intermediary etching stopper layer that enables precise depth control of through-holes. By positioning the cured film between the AlO barrier film and the oxide semiconductor, the etching process can be controlled to stop at the cured film interface, preventing over-etching and penetration of the drain or source electrodes while still achieving the necessary connectivity.
3Adaptability or versatility
If over-etching occurs during through-hole formation, then connectivity is improved, but electrode integrity is compromised and TFT becomes inoperable
Solution Approach 1:
The cured film is positioned in advance as a protective layer that prevents over-etching from damaging the electrode structures. This preliminary protective action ensures that even if etching conditions vary or proceed too far, the cured film stops the etching process before the drain or source electrodes are compromised, maintaining electrode integrity and TFT operability.
Solution Approach 2:
The cured film acts as a cushioning layer that absorbs the variability in etching processes. By having this additional layer in place beforehand, the system is cushioned against the harmful effects of over-etching, allowing the etching process to proceed with more tolerance while still protecting the underlying electrode structures from damage.
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 stabilizes the operation of oxide semiconductor TFTs by precisely controlling the depth of through-holes, preventing electrode penetration and maintaining electrical connectivity, thus ensuring the TFTs' operational stability and reliability.
Implementation Method 1
A TFT circuit structure is implemented with a cured film acting as an etching stopper under the AlO film, allowing precise control of through-hole formation using two-stage dry etching
Implementation Method 2
it is necessary to prevent moisture or the like from reaching the oxide semiconductor by providing a barrier film because the properties of the oxide semiconductor are subject to change under the influence of moisture
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.