Etchant for Copper-Titanium Films in Thin Film Transistors
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Solution Overview
Problem
Conventional etchants cause critical dimension loss and yield rate deterioration when etching multi-layered copper/titanium or copper/titanium alloy films, leading to non-uniform pattern profiles and increased fabrication costs due to frequent replacements.
Innovation Solution
An etchant comprising fluorine ions, hydrogen peroxide, sulfate, phosphate, and an azole-based compound is used to etch multi-layered films, maintaining uniformity and extending the etchant's usage life by minimizing performance deterioration with increasing substrate numbers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etchants are used to etch multi-layered copper/titanium films, then the etching process can be completed, but critical dimension loss occurs and yield rate deteriorates due to non-uniform pattern profiles
Solution Approach 1:
The patent modifies the chemical composition parameters of the etchant by incorporating specific concentrations of hydrogen peroxide (1-10 wt%), sulfate (0.1-5 wt%), phosphate (0.1-5 wt%), fluoride compound (0.001-0.5 wt%), and organic amine compound (0.1-5 wt%). This parameter optimization enables simultaneous etching of copper and titanium layers with uniform pattern profiles, eliminating critical dimension loss and maintaining high yield rates even after etching multiple substrates.
Solution Approach 2:
The patent creates a composite etchant formulation that combines multiple chemical components (hydrogen peroxide, sulfate, phosphate, fluoride compound, and organic amine compound) to achieve synergistic effects. This composite etchant can simultaneously etch different metal layers (copper and titanium) with appropriate selectivity and uniformity, resolving the issue of non-uniform pattern profiles that occurs with conventional single-component etchants.
2Productivity
If conventional etchants are used for multiple substrate etching, then production can continue, but etching performance deteriorates requiring frequent etchant replacement
Solution Approach 1:
The patent formulates an etchant with stabilized chemical components that maintain consistent etching performance over extended use. The hydrogen peroxide is stabilized at 1-10 wt% concentration and the organic amine compound (0.1-5 wt%) acts as a stabilizer, allowing the etchant to continuously etch multiple substrates (more than 100 sheets) without performance deterioration, eliminating the need for frequent replacement and ensuring continuous productive action.
Solution Approach 2:
The patent optimizes the concentration parameters of stabilizing agents (organic amine compound at 0.1-5 wt%) and oxidizing agents (hydrogen peroxide at 1-10 wt%) to maintain etching performance consistency. This parameter control ensures that the etchant maintains uniform etching rates and pattern quality across multiple substrate batches, enabling continuous production without quality degradation.
3Reliability
If copper is used as wire material to reduce resistivity, then signal delay is reduced, but adherence to glass substrate deteriorates and reaction with silicon buffer occurs
Solution Approach 1:
The patent uses a composite metal structure (copper/titanium or copper/titanium alloy) where copper provides low resistivity (2.2μΩcm) for reduced signal delay, while titanium provides strong adherence to glass substrate and prevents copper-silicon reactions. The etchant is specifically designed to etch this composite structure uniformly, maintaining the beneficial properties of both materials without their individual drawbacks.
Solution Approach 2:
The titanium layer acts as an intermediary between copper and the glass substrate/silicon buffer. It provides mechanical anchoring to the substrate and acts as a diffusion barrier preventing copper from reacting with silicon. The patent's etchant simultaneously etches both copper and titanium layers, maintaining the integrity of this protective intermediary structure while enabling low-resistance electrical connections.
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 ensures high-yield, cost-effective fabrication of thin film transistors with improved pattern profiles and reduced signal delay, enabling the production of large-sized, high-resolution displays with stable etching performance over multiple substrate batches.
Implementation Method 1
The etchant includes hydrogen peroxide, which serves as an oxidizing agent to facilitate the etching of copper and titanium layers through oxidation reactions
Implementation Method 2
The etchant includes fluorine ions that specifically react with titanium to form soluble titanium fluoride compounds, enabling selective removal of titanium layers
Implementation Method 3
The etchant includes sulfate and phosphate salts that form complexes with metal ions, controlling etching rates and preventing precipitation of unwanted byproducts
Implementation Method 4
The etchant includes an azole-based compound that serves as a chelating agent to bind metal ions in solution, preventing unwanted side reactions and stabilizing the etchant composition
Data Source
Figure 1
Figure 2A~2D
Figure 2E
AI summary
An etchant and a method of fabricating an electric device including a thin film transistor. The etchant includes a fluorine ion (F-) source, hydrogen peroxide (H2O2), a sulfate, a phosphate, an azole-based compound, and a solvent. The etchant and method of fabricating an electric device including a thin film transistor, can etch a multilayered film including copper layer, and a titanium or titanium alloy layer in a batch and can provide a thin film transistor having a good pattern profile at high yield. When reusing the etchant, uniform etching performance can be maintained with a long replacement period of the etchant, and therefore costs can be saved.