Copper Electroplating Bath Additives for Uniform Pillar Morphology
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Solution Overview
Problem
Current copper electroplating methods for photoresist defined features, such as copper pillars and redistribution layer wiring, face challenges in achieving uniform surface morphology, with improvements in one attribute often coming at the expense of another, leading to defects that compromise the performance of advanced packaging articles.
Innovation Solution
A copper electroplating method using a bath comprising reaction products of imidazole compounds, bisepoxides, and halobenzyl compounds, along with electrolytes, accelerators, and suppressors, to achieve copper photoresist features with an average % TIR of 5% to 10% and % WID of 8% to 10%, resulting in substantially uniform morphology and flat profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional copper electroplating methods are used, then copper features can be formed, but the surface morphology is non-uniform with defects
Solution Approach 1:
The patent modifies the electroplating bath chemistry by incorporating specific additives (polyethylene glycol, polypropylene oxide, and sulfur compounds) to change the deposition parameters. This results in uniform surface morphology with 5% to 10% TIR while maintaining feature uniformity through controlled electrochemical reactions.
Solution Approach 2:
The patent introduces intermediary substances (leveling agents and brighteners) into the electroplating bath to mediate the copper deposition process. These additives adsorb on the growing copper surface to control morphology and prevent defects, acting as intermediaries between the copper ions and the substrate.
2Manufacturing precision
If electroplating is optimized for one attribute, then that attribute improves, but other attributes deteriorate
Solution Approach 1:
The patent achieves both high feature uniformity (5% to 10% TIR) and high deposition rates by optimizing multiple bath parameters simultaneously, including additive concentrations, temperature, and pH. This multi-parameter optimization enables simultaneous improvement of precision and productivity.
Solution Approach 2:
The electroplating bath uses a composite chemistry system combining multiple additives (polyethylene glycol, polypropylene oxide, sulfur compounds) working together to achieve both uniform feature formation and high deposition rates, leveraging synergistic effects of different chemical components.
3Productivity
If copper pillars are plated with high deposition rates, then productivity increases, but surface morphology uniformity decreases
Solution Approach 1:
The patent employs intermediary leveling agents that adsorb on high-points of the growing copper surface during rapid deposition, preventing excessive growth and maintaining surface flatness. These intermediaries enable high deposition rates while preserving morphology uniformity.
Solution Approach 2:
The patent modifies deposition parameters through additive chemistry to maintain surface flatness during high-rate plating. The additives change the electrochemical reaction kinetics to favor uniform surface growth even at high current densities, enabling both high productivity and surface quality.
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 provides copper photoresist features with a smooth, nodule-free surface, enabling reliable copper pillar structures and improved performance in advanced packaging applications by maintaining uniformity and flatness, thus enhancing the reliability and efficiency of copper electroplating processes.
Implementation Method 1
The substrate with the patterned photoresist is then immersed in a metal electroplating bath, typically a copper electroplating bath, and metal is electroplated in the circuit line pattern or aperture to form features such as pillars, bond pads or circuit lines
Implementation Method 2
electroplating a plurality of copper photoresist defined features in the plurality of apertures
Data Source
AI summary
Electroplating methods enable the plating of photoresist defined features which have substantially uniform morphology. The electroplating methods include copper electroplating baths with reaction products of imidazole compounds, bisepoxides and halobenzyl compounds to electroplate the photoresist defined features. Such features include pillars, bond pads and line space features.