Double Metal Layer Etching Composition for TFT-LCD Array Substrates
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Solution Overview
Problem
The existing etching methods for double metal layers of aluminum neodymium (AlNd) and molybdenum (Mo) in TFT-LCD devices face challenges such as overhang structures, molybdenum tails, and aluminum neodymium residues, leading to electrical shorts, image stains, and non-uniform profiles due to differences in etch rates and poor wettability.
Innovation Solution
A composition comprising 63.5% to 64.5% phosphoric acid, 8% to 9% nitric acid, 8% to 12% acetic acid, and an anionic additive is used to etch the double metal layer, ensuring uniformity and preventing defects like overhangs and residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single etchant is used to etch both aluminum neodymium and molybdenum layers, then the etching process is simplified, but non-uniform etching rates cause overhang structures and poor profile uniformity
Solution Approach 1:
The patent modifies the chemical composition parameters of the etchant by adding specific organic additives (carboxylic acid and alcohol) to the phosphoric acid-based etchant. This parameter change enables simultaneous etching of AlNd and Mo layers with uniform rates, resolving the contradiction between process simplicity and profile uniformity without requiring multiple etching steps
2Reliability
If aluminum neodymium layer is over-etched to remove residues, then complete pattern formation is achieved, but molybdenum layer is damaged and overhang structures are created
Solution Approach 1:
The patent introduces organic intermediary substances (carboxylic acid and alcohol additives) that mediate the etching reaction between the etchant and metal layers. These intermediaries modify the etching mechanism to achieve uniform removal of both AlNd and Mo layers simultaneously, preventing both over-etching damage and residue formation without creating overhang structures
3Manufacturing precision
If aluminum neodymium layer has poor wettability, then etching is incomplete and residues remain, but increasing etching aggressiveness damages the molybdenum layer
Solution Approach 1:
The patent changes the chemical parameters of the etchant by incorporating carboxylic acid and alcohol additives that improve wettability on aluminum neodymium surfaces. This enables complete etching of the AlNd layer without requiring aggressive etching conditions that would damage the underlying molybdenum layer, thus eliminating residues while preserving layer integrity
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 solution achieves a uniform double metal line without molybdenum tails or aluminum neodymium residues, improving display device resolution, preventing electrical issues, and eliminating image stains.
Implementation Method 1
a composition for etching a double metal layer includes: about 63.5% to about 64.5% by weight of a phosphoric acid; about 8% to about 9% by weight of a nitric acid; about 8% to about 12% by weight of an acetic acid; and an anionic additive
Data Source
AI summary
A composition for etching a double metal layer, a method of fabricating an array substrate using the composition, and a method of forming a double metal line using the composition are provided. The composition includes about 63.5% to about 64.5% by weight of a phosphoric acid; about 8% to about 9% by weight of a nitric acid; about 8% to about 12% by weight of an acetic acid; and an anionic additive.