Universal Etchant for TFT Conductive Layers
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Solution Overview
Problem
The manufacturing of thin film transistor array panels for LCDs faces challenges due to the use of conductive materials with low resistivity, which are vulnerable to etchants, leading to defective profiles such as undercut and overhang, and the complexity of using different etchants for various materials increases costs and complicates the process.
Innovation Solution
An etchant composition of 65-75 wt% phosphoric acid, 0.5-15 wt% nitric acid, 2-15 wt% acetic acid, 0.1-8.0 wt% potassium compound, and deionized water is used, which includes potassium nitrate and potassium acetate, to uniformly etch conductive layers and reduce galvanic effects, resulting in improved profile stability and etching uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a metal having low resistivity is used for signal lines, then electrical conductivity is improved, but chemical resistance deteriorates causing vulnerability to etchant damage
Solution Approach 1:
The patent combines multiple etchants (phosphoric acid, nitric acid, acetic acid, and potassium compound) into a single unified etching solution that can effectively etch multiple different conductive materials (aluminum, molybdenum, ITO) with different chemical properties, eliminating the need for separate etching processes for each material layer
Solution Approach 2:
The developed etching solution serves multiple functions: it can etch aluminum-based conductors, molybdenum-based conductors, and ITO transparent conductors using the same solution and process conditions, making the etching system universal for all conductive patterns in the TFT array panel
2Manufacturing precision
If different etchants are used for different conductive materials, then etching precision is improved, but device complexity increases
Solution Approach 1:
The patent develops a universal etching solution containing phosphoric acid (65-75 wt%), nitric acid (0.5-15 wt%), acetic acid (2-15 wt%), and potassium compound (0.1-8.0 wt%) that can etch multiple conductive materials (Al, Mo, ITO) with the same solution, reducing the number of etching processes from multiple separate steps to a single unified process
Solution Approach 2:
The patent merges the functionality of multiple material-specific etchants into a single combined etching solution that maintains effective etching performance for all conductive layers while simplifying the overall manufacturing process flow
3Productivity
If conventional etchants are used on low resistivity metals, then etching speed is improved, but manufacturing precision deteriorates due to undercut and overhang defects
Solution Approach 1:
The patent modifies the chemical composition parameters of the etching solution by adding potassium compounds (such as potassium nitrate or potassium acetate) to the phosphoric acid-based solution, which changes the etching mechanism to achieve both high etching speed and vertical profile formation without undercut or overhang defects
Solution Approach 2:
The patent creates a composite etching solution that combines phosphoric acid (primary etching agent), nitric acid (oxidizing agent), acetic acid (complexing agent), and potassium compound (profile control agent), where each component contributes to achieving both fast etching speed and precise profile control
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 proposed etchant ensures conductive layers are etched with good side slopes and critical dimensions without undercut or overhang, uniformly across the substrate, simplifying the manufacturing process and reducing costs while enhancing product quality.
Implementation Method 1
The etchant ensures conductive layers are etched with good side slopes and critical dimensions without undercut or overhang
Implementation Method 2
An etchant composition of 65-75 wt% phosphoric acid, 0.5-15 wt% nitric acid, 2-15 wt% acetic acid, 0.1-8.0 wt% potassium compound
Implementation Method 3
uniformly etch conductive layers and reduce galvanic effects, resulting in improved profile stability and etching uniformity
Data Source
AI summary
The present invention provides a method for manufacturing a thin film transistor (TFT) array panel by forming a gate line having a gate electrode on an insulating substrate; sequentially depositing a gate insulating layer and a semiconductor layer on the gate line; forming a drain electrode and a data line having a source electrode on the gate insulating and semiconductor layers; and forming a pixel electrode connected to the drain electrode. These elements can be formed by photo-etching using an etchant containing 65 wt % to 75 wt % of phosphoric acid, 0.5 wt % to 15 wt % of nitric acid, 2 wt % to 15 wt % of acetic acid, 0.1 wt % to 8.0 wt % of a potassium compound, and deionized water. Each element of the TFT array panel can be patterned with the etchant of the invention under similar conditions, which simplifies a manufacturing process and saves costs and results in TFT elements having a good profile.