Tapered Organic Etch-Stopper Layer for TFT Hump Phenomenon
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Solution Overview
Problem
The use of organic materials for the etch-stopper layer in etch-stopper thin-film transistors results in a 'hump phenomenon' in transistor characteristics, particularly in regions where current rapidly increases, which is critical for organic EL displays, especially in black display regions.
Innovation Solution
Incorporating an altered layer in the etch-stopper layer with a specific defect density and taper angle relationship, where Log10 Nt≦0.0556θ+16.86, generated by dry etching, to reduce the hump phenomenon by altering the surface layer and adjusting the edge portion taper angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic materials are used for the etch-stopper layer, then the channel layer can be protected from etching damage, but a marked hump phenomenon appears in the transistor characteristics
Solution Approach 1:
The patent applies parameter changes by modifying the physical and chemical properties of the etch-stopper layer through controlled dry etching treatment. Specifically, the etch-stopper layer is subjected to dry etching with optimized parameters (gas composition, power, pressure, time) to create an altered layer with modified defect density and reduced organic material concentration at the interface, thereby suppressing the hump phenomenon while maintaining etch protection function
Solution Approach 2:
The patent implements preliminary action by performing dry etching treatment on the etch-stopper layer before subsequent transistor fabrication steps. This pre-treatment modifies the etch-stopper layer surface and interface properties in advance, preventing the formation of harmful byproducts and reducing defect density before the channel layer is fully processed, thus eliminating the hump phenomenon in the final device characteristics
2Reliability
If the channel layer is made thinner to improve turn-on characteristics, then parasitic resistance is reduced, but the channel layer becomes more vulnerable to etching damage
Solution Approach 1:
The patent uses the etch-stopper layer as an intermediary protective element between the etching process and the thin channel layer. By optimizing the etch-stopper layer properties through dry etching treatment (reducing organic material concentration and defect density), it provides effective protection to the thin channel layer during subsequent processing steps, enabling the channel layer to be made thinner without suffering etching 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 configuration significantly reduces the hump phenomenon in current-voltage characteristics, enhancing transistor performance and suitability for organic EL displays, particularly in low gray scale regions.
Implementation Method 1
The altered layer is generated by alteration of a surface layer of the etch-stopper layer in a region exposed from the source electrode and the drain electrode
Data Source
AI summary
A thin-film transistor includes: a gate electrode above a substrate; a gate insulating layer above the gate electrode; a semiconductor layer opposed to the gate electrode with the gate insulating layer therebetween; a protective layer above the semiconductor layer and comprising an organic material; and a source electrode and a drain electrode each of which has at least a portion located above the protective layer. The protective layer includes an altered layer which has at least a portion contacting the semiconductor layer, and which is generated by alteration of a surface layer of the protective layer in a region exposed from the source electrode and the drain electrode. A relational expression of Log10 Nt≦0.0556θ+16.86 is satisfied where Nt (cm−3) represents a defect density of the semiconductor layer and θ (°) represents a taper angle of an edge portion of the protective layer.