Copper Wire Etchant Composition for TFT Manufacturing
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Solution Overview
Problem
Copper wire etching in thin film transistor manufacturing faces challenges due to copper's poor adhesion to glass substrates and silicon insulating layers, leading to instability and high costs with peroxide-based etchants, and existing etchants struggle with maintaining stability and process margins.
Innovation Solution
A metal wire etchant comprising persulfate, sulfonate, a fluorine compound, an azole-based compound, organic acid, nitrate, and a chlorine compound is used to etch copper and lower metal layers, ensuring high stability and uniform etching, with specific weight ratios and components to control etch rates and prevent defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If peroxide-based etchant is used to etch copper layer, then etching speed is improved, but stability deteriorates due to heat emission and rapid composition change
Solution Approach 1:
The patent changes the chemical composition parameters of the etchant by replacing peroxide-based components with a combination of ammonium persulfate, sulfuric acid, and buffer components. This parameter change maintains effective etching speed while improving stability by eliminating the rapid decomposition and heat emission issues associated with peroxide-based etchants.
Solution Approach 2:
The patent uses ammonium persulfate as a stable, cost-effective alternative to expensive peroxide stabilizers. The etchant formulation achieves the desired etching performance without requiring costly stabilizing agents, making the process more economically viable while maintaining stability.
2Reliability
If copper is used as wire material, then electrical resistance is reduced, but adhesion deteriorates on glass substrate and silicon insulating layer
Solution Approach 1:
The patent employs a dual-layer etching approach where the etchant selectively removes copper while preserving the adhesion between copper and the underlying metal layer (such as molybdenum or titanium). This intermediary layer structure maintains both the electrical conductivity benefits of copper and the adhesion strength required for reliable device performance.
Solution Approach 2:
The etching process applies different etching rates to different layers: aggressive etching for copper removal while gentle etching preserves the metal-insulator interface. This local quality control ensures that copper achieves its low-resistance properties while the underlying layers maintain strong adhesion to the substrate and insulating layers.
3Productivity
If circuit line is made thinner for size reduction, then integration is improved, but electrical resistance increases
Solution Approach 1:
The patent enables thinner circuit lines to be etched with precise control over etch rate and profile. By optimizing the etchant composition (ammonium persulfate, sulfuric acid, buffer components), the process achieves uniform etching of thin copper layers while maintaining electrical conductivity, allowing higher integration density without sacrificing performance.
4Stability of the object's composition
If peroxide stabilizer is added to solve stability problems, then stability is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive peroxide stabilizers with a cost-effective formulation based on ammonium persulfate, sulfuric acid, and buffer components. This alternative chemistry achieves the required stability without needing costly additives, significantly reducing manufacturing costs while maintaining etchant performance and stability throughout the process.
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
The etchant achieves stable and uniform etching of copper layers, maintaining process margins, reducing defects, and controlling etch rates, while minimizing waste heat emission and manufacturing costs.
Implementation Method 1
an etching process of implementing a desired line path of an electric circuit by corroding the metal layer by gas or a solution having a corrosion property
Implementation Method 2
persulfate, sulfonate, a fluorine compound, an azole-based compound, organic acid, nitrate, and a chlorine compound
Data Source
AI summary
A metal wire etchant including persulfate, a sulfonate, a fluorine compound, an azole-based compound, an organic acid, a nitrate, and a chlorine compound, and a method of making the same.