IGZO TFT Source-Drain Etching via Selective Conductive Layer
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Solution Overview
Problem
The active layer of Indium-Gallium-Zinc Oxide (IGZO) Thin Film Transistors (TFTs) is prone to corrosion during the Back Channel Etch (BCE) process due to poor chemical stability, making it difficult to implement this process effectively.
Innovation Solution
Incorporating a first conductive layer with a higher etching rate than the active layer material, allowing for reduced damage during the etching process for the source and drain electrodes, thereby enabling the use of the back channel etch process without an etch blocking layer and simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a Back Channel Etch (BCE) process is used to fabricate the IGZO TFT, then the preparation process is simplified and cost is reduced, but the active layer is easily corroded due to poor chemical stability
Solution Approach 1:
The patent introduces an etch blocking layer as an intermediary between the etching liquid and the active layer. This layer selectively protects the active layer from corrosion while allowing the etching process to proceed on the source and drain electrode regions. The etch blocking layer acts as a mediator that enables the BCE process to be applied without directly exposing the chemically unstable active layer to the etching liquid, thus resolving the contradiction between process simplification and chemical stability
Solution Approach 2:
The patent applies different protective measures to different regions of the device. The etch blocking layer is selectively positioned to cover only the active layer regions that require protection during etching, while leaving other regions exposed for proper etching. This local differentiation allows the BCE process to be performed with simplified overall structure while maintaining local chemical stability where needed
2Reliability
If an etch blocking layer is added to protect the active layer, then chemical stability is improved, but device complexity increases
Solution Approach 1:
The patent combines the etch blocking layer function with existing device structures. The etch blocking layer is integrated into the multi-layer conductive structure of the source and drain electrodes, where it serves dual purposes: protecting the active layer during etching and maintaining electrical conductivity in the electrode regions. This merging approach adds minimal structural complexity while achieving the required chemical stability
3Strength
If the etching rate of the source and drain electrode material is lower than the active layer, then the source and drain electrodes are better protected, but the active layer suffers greater corrosion damage
Solution Approach 1:
The etch blocking layer serves as a mediator that reverses the protective relationship. Instead of relying on the source and drain electrode materials to protect the active layer through slower etching rates, the etch blocking layer is positioned to directly protect the active layer from etching liquid exposure. This intermediary approach ensures the active layer is protected regardless of the relative etching rates of other materials
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 reduces damage to the active layer, lowers manufacturing costs, and maintains good conductivity of the source and drain electrodes, enhancing the overall performance of the thin film transistor.
Implementation Method 1
an etching rate of a material of the first conductive layer is greater than an etching rate of a material of the active layer in an etching liquid
Data Source
AI summary
A thin film transistor and a fabrication method thereof, an array substrate and a display device are provided. The thin film transistor comprises a gate electrode, an active layer, a source electrode and a drain electrode. The source electrode and the drain electrode include a first conductive layer provided on the active layer, and an etching rate of a material of the first conductive layer is greater than an etching rate of a material of the active layer in an etching liquid. The problem that the active layer of the thin film transistor is easily corroded in a back channel etch process is avoided, a number of patterning processes is reduced, and fabrication cost is reduced.