Heterocyclic Leveling Agents for Uniform Copper Plating
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Solution Overview
Problem
Conventional copper electroplating baths struggle to achieve uniform copper deposits on substrates with irregular topography, particularly in PCBs containing both through-holes and blind vias, as existing leveling agents compromise throwing power and result in uneven metal layers with defects like nodules.
Innovation Solution
A copper electroplating bath comprising a source of copper ions, an electrolyte, and a leveling agent formed by reacting benzimidazole compounds with epoxide-containing compounds, which maintains throwing power while providing level copper deposits and minimizing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional leveling agents are used in copper electroplating baths, then surface uniformity of copper deposit is improved, but throwing power deteriorates resulting in poor via filling
Solution Approach 1:
The patent modifies the chemical structure of leveling agents by using specific heterocyclic compounds (pyridine, pyrimidine, triazine, tetrazine rings) with controlled molecular weights (500-5000) and functional groups. These parameter changes in the additive structure maintain surface leveling capability while reducing negative impact on throwing power, enabling effective via filling.
Solution Approach 2:
The electroplating bath uses a composite additive system combining specially designed heterocyclic leveling agents with accelerators and brighteners. This composite formulation achieves synergistic effects where the heterocyclic compound provides leveling while other components maintain throwing power and deposit quality, resolving the contradiction between surface uniformity and via filling.
2Manufacturing precision
If accelerator and leveler additives are used to improve deposit uniformity, then surface quality is improved, but voltage drop variation is exacerbated leading to overplating
Solution Approach 1:
The heterocyclic leveling agent provides localized control of copper deposition by selectively adsorbing on protruding surface areas. The compound's functional groups (carboxyl, hydroxyl, amino) create local inhibition zones that prevent excessive deposition on high spots while allowing normal plating in recessed areas, thus achieving uniformity without exacerbating voltage drop effects.
Solution Approach 2:
The heterocyclic compound acts as an intermediary substance that mediates between the copper ions and the substrate surface. It forms a controlled barrier layer that regulates copper ion transport to the cathode, smoothing out voltage drop variations and preventing overplating while maintaining deposit uniformity.
3Manufacturing precision
If conventional leveling agents are used, then some surface leveling is achieved, but nodule formation and voids increase reducing deposit quality
Solution Approach 1:
The patent specifies precise molecular weight ranges (500-5000) and structural parameters for heterocyclic compounds to optimize their performance. These parameter changes ensure the leveling agents form uniform adsorption layers without causing nodular deposits or void formation, improving surface quality while maintaining deposit integrity.
Solution Approach 2:
The heterocyclic leveling agents are designed to be consumed during the plating process, forming temporary protective layers that guide copper deposition. These short-living organic compounds are replaced continuously to maintain optimal performance, preventing nodule formation and voids while achieving surface leveling.
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 deposits copper with reduced defects and improved uniformity across substrates, including those with small features and varying aperture sizes, maintaining high throwing power and minimizing voids and nodules.
Implementation Method 1
A copper electroplating bath and method for depositing copper on a substrate
Implementation Method 2
passing a current between two electrodes in a plating solution where one of the electrodes is the article to be plated
Implementation Method 3
leveling agents used in copper plating baths provide better leveling of the deposit across the substrate surface
Data Source
AI summary
Copper plating baths containing a leveling agent that is a reaction product of a certain benzimidazole with a certain epoxide-containing compound that deposit copper on the surface of a conductive layer are provided. Such plating baths deposit a copper layer that is substantially planar on a substrate surface across a range of electrolyte concentrations. Methods of depositing copper layers using such copper plating baths are also disclosed.