Copper Nano Etching Predip for Line Shape Retention
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Solution Overview
Problem
Conventional etching methods for copper and copper alloys in the electronics industry face challenges such as undesired undercutting, line shape alteration, and excessive line width reduction, leading to insufficient adhesion and circuit shorts, particularly in semi-additive and modified semi-additive processes.
Innovation Solution
A method involving a predip composition with sulfur-containing compounds followed by an etching solution containing oxidizing agents, acids, and halide ions to maintain geometrical structure and adhesion, while minimizing line width reduction and undercutting, using a non-etching predip step and an etching step with specific sulfur-containing compounds and oxidizing agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching solutions (oxidizing agent + acid) are used, then copper etching is achieved, but line shape deterioration occurs including undercutting, line width reduction, and loss of rectangular geometry
Solution Approach 1:
A predip composition containing sulfur-containing compounds (such as benzothiazole derivatives) is applied before etching to form a protective layer on the copper surface. This intermediary layer modifies the etching behavior by controlling oxidizing agent distribution and reaction kinetics, thereby preserving line shape and reducing undercutting while maintaining etching effectiveness.
Solution Approach 2:
The patent modifies the chemical parameters of the etching system by introducing sulfur-containing compounds that change the etching kinetics. These compounds alter the oxidation rate and copper ion dissolution behavior, resulting in more uniform etching profiles with reduced line width reduction and better geometric retention.
2Strength
If oxide layer formation and reduction is used to promote adhesion, then adhesion between copper and resin is improved, but geometric shape of the oxide layer is lost
Solution Approach 1:
The sulfur-containing compounds in the predip composition act as intermediaries that facilitate adhesion promotion through controlled surface modification. They form a protective sulfur-based layer that enhances adhesion between copper and subsequent resin layers without requiring complete oxide formation and reduction cycles, thereby preserving geometric integrity.
3Manufacturing precision
If etching is performed to remove seed layer in semi-additive process, then copper track formation is achieved, but differential etching behavior between electroless and electroplated copper leads to line shape alteration
Solution Approach 1:
The sulfur-containing compounds in the predip composition provide local quality modification by preferentially adsorbing on electroless plated copper surfaces (which have finer grain structure). This creates different etching resistance on different copper layers, enabling controlled differential etching that removes seed layer while preserving the rectangular shape and preventing line shape alteration.
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 method achieves improved retention of rectangular line shape, enhanced adhesion between copper and dielectric materials, reduced signal loss, and minimal peel strength drop after Highly Accelerated Stress Test, maintaining ultra-low surface roughness and preventing line shape deterioration.
Implementation Method 1
the predip composition comprises at least one sulfur-containing compound
Implementation Method 2
the etching solution comprises at least one oxidizing agent suitable to oxidize copper
Implementation Method 3
the etching solution comprises at least one acid
Data Source
Figure 1A~1D
Figure 2
Figure 2
AI summary
Method for nano etching of copper or copper alloy surfaces characterized by the following method steps: i) providing a substrate having at least one copper or copper alloy surface, ii) contacting at least a portion of said copper or copper alloy surface with a predip composition, iii) contacting at least a portion of said copper or copper alloy surface with an etching solution, characterized in that - the steps are performed subsequently; - step ii) is a non-etching step; - step iii) is an etching step; and - the predip composition comprises at least one sulfur-containing compound selected from a list defined in the claims.