Thin Film Transistor Low Dielectric Buffer Layer Threshold Voltage Stability
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Solution Overview
Problem
Thin film transistors on flexible substrates, such as metal thin films, experience changes in threshold voltage due to unintended voltages or static charges, affecting display characteristics like color coordinates, gray scale, and contrast.
Innovation Solution
A thin film transistor structure with a low dielectric constant buffer layer (1.2 to 4) and a diffusion prevention layer, using materials like SiOC, Xerogels, Silsesquioxanes, and SiOF, is implemented between the substrate and semiconductor layer to minimize electrical characteristic changes, including threshold voltage shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buffer layer with high dielectric constant is used, then good insulation performance is achieved, but threshold voltage changes due to charge accumulation increase
Solution Approach 1:
The patent changes the dielectric constant parameter of the buffer layer from high to low (specifically using materials with dielectric constant less than 3.9, preferably less than 2.5). This parameter change reduces the layer's ability to accumulate charges while maintaining insulation function, thereby stabilizing the threshold voltage against changes caused by static electricity or unintended voltages.
Solution Approach 2:
The low dielectric constant buffer layer acts as an intermediary between the metal thin film substrate and the semiconductor layer. It mediates the electrical interaction by preventing charge accumulation that would otherwise occur in high dielectric constant materials, thus protecting the threshold voltage from unwanted changes while still providing necessary insulation.
2Reliability
If DC voltage or predetermined signal is applied to control threshold voltage, then operation stability is improved, but threshold voltage becomes sensitive to unintended voltages and static charges
Solution Approach 1:
The patent converts the harmful effect of the buffer layer (potential charge accumulation in high dielectric constant materials) into a beneficial property by selecting low dielectric constant materials. These materials inherently resist charge accumulation, thus converting what could be a source of instability into a protective feature that immune the transistor to unintended voltages and static charges.
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 configuration significantly reduces electrical characteristic changes in the thin film transistor, maintaining stable operation and display quality by minimizing charge accumulation and external noise impact.
Implementation Method 1
a buffer layer having a low dielectric constant from about 1.2 to 4.0 and formed on the substrate
Data Source
AI summary
A thin film transistor and a method for manufacturing the same capable of reducing a change in a threshold voltage of the thin film transistor formed on a flexible substrate. The thin film transistor includes: a substrate, the substrate being flexible; a buffer layer having a low dielectric constant from about 1.2 to about 4.0 and formed on the substrate; a semiconductor layer formed on the buffer layer; a gate electrode; first insulation layer formed between the gate electrode and the semiconductor layer; a second insulation layer formed on the semiconductor layer and the gate electrode; and a source/drain electrode electrically connected to the semiconductor layer through a contact hole formed in the second insulation layer. Therefore, the thin film transistor can reduce a change in its threshold voltage, thereby reducing changes in brightness, gray scale, contrast, etc., of light-emitting devices using the thin film transistor.