Etching Solution for Copper Selectivity and Foam Reduction
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Solution Overview
Problem
Existing etching solutions for copper or copper alloys in electronic substrates often generate foam, leading to malfunctions in sensor detection and air entrainment issues, which can cause deformation of bumps and disrupt the etching process, especially when both copper and nickel are present.
Innovation Solution
An etching solution comprising linear alkanolamine, a chelating agent with an acid group, and hydrogen peroxide is used to selectively etch copper or copper alloys, minimizing foam generation and ensuring high selectivity between copper and nickel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching solutions (sulfuric acid + hydrogen peroxide) are used to etch copper seed layer, then etching capability is achieved, but foam is generated causing sensor malfunction and pump air entrainment
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by replacing conventional sulfuric acid-based formulations with a novel composition containing oxalic acid (0.1-10 wt%), hydrogen peroxide (1-20 wt%), and specific surfactants. This parameter change eliminates foam generation while maintaining effective copper etching capability, resolving the contradiction between reliable etching and harmful foam production.
Solution Approach 2:
The patent employs a readily available, inexpensive chemical formulation using common laboratory reagents (oxalic acid, hydrogen peroxide, water) that can be easily prepared and disposed of. This approach replaces complex, expensive conventional etchants with a simple, cost-effective solution that achieves the same etching function without foam issues.
2Productivity
If etching solution contacts nickel layer during copper etching, then copper removal is achieved, but nickel etching occurs causing bump deformation
Solution Approach 1:
The etching solution exhibits selective chemical reactivity - it is formulated to have high etching capability for copper while being inert to nickel. The local quality of chemical aggressiveness is tailored specifically for copper oxidation and dissolution, allowing rapid copper removal without affecting the nickel barrier layer or bump structure, thus achieving both high productivity and manufacturing precision.
Solution Approach 2:
The patent uses surfactants (Tween 80, Triton X-100, or Nonidet P-40) as intermediary substances that modify the chemical environment. These surfactants facilitate copper etching by enhancing reagent access and reaction efficiency, while simultaneously providing selective protection to nickel surfaces, preventing unwanted nickel etching and maintaining bump 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 effectively reduces foam formation, allowing for precise etching of copper or copper alloys with high selectivity, preventing nickel etching and maintaining the integrity of electronic substrate features.
Implementation Method 1
the solution comprises, as essential components, (A) a linear alkanolamine, (B) a chelating agent having an acid group in the molecule thereof, and (C) hydrogen peroxide
Implementation Method 2
a chelating agent having an acid group in the molecule thereof
Data Source
AI summary
Object is to provide an etching solution which generates less foam and can etch copper or copper alloy at high selectivity when used in a step of etching copper or 5 copper alloy in an electronic substrate having both of copper or copper alloy and nickel. The etching solution to be used in a step of selectively etching copper or copper alloy in an electronic substrate having both of copper or copper alloy and nickel has, as essential components thereof, (A) a linear alkanolamine, (B) a chelating agent having an acid group in the molecule thereof, and (C) hydrogen peroxide.