Copper Electroplating via Filling Stability
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Solution Overview
Problem
Copper electroplating solutions containing sulfur atoms become unstable over time, leading to poor via filling ability and plating appearance issues, especially due to the formation of decomposition products that affect deposition rates and adhesion of the copper layer.
Innovation Solution
A copper electroplating solution using sulfur-containing compounds and aliphatic semialdehydes, such as semialdehyde succinate, is employed to reduce the concentration of decomposition products, thereby maintaining stable plating performance and improving via filling ability without using formaldehyde.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If copper electroplating baths containing sulfur-containing compounds are used to promote deposition rates near the bottom surface of vias, then via filling ability is improved, but the plating bath becomes unstable over time causing lumps to form in the copper electroplating layer
Solution Approach 1:
The invention changes the chemical parameters of the plating bath by introducing specific organic compounds (sulfonated condensates of formaldehyde and sulfur-containing compounds, along with aliphatic semialdehydes) that modify the deposition characteristics. These parameter changes enable sustained via filling ability without the instability and lump formation that occurs with conventional sulfur-containing compounds alone.
2Speed
If conventional sulfur-containing compounds are used in copper electroplating, then deposition rate near via bottom is improved, but plating appearance deteriorates and filling becomes unstable over time
Solution Approach 1:
The invention uses a composite chemical system consisting of sulfonated condensates (formaldehyde-sulfur compound adducts) combined with aliphatic semialdehydes. This composite approach creates synergistic effects that maintain both high deposition rates and stable, lump-free plating over extended periods, resolving the reliability issues of single-component systems.
3Manufacturing precision
If formaldehyde is used to improve via filling ability, then filling performance is enhanced, but environmental and safety concerns arise due to low flash point and health effects
Solution Approach 1:
The invention introduces sulfonated condensates as intermediary compounds that capture and modify the function of formaldehyde. These condensates serve as stable carriers that provide the necessary via filling enhancement while eliminating formaldehyde's direct environmental and safety hazards. The aliphatic semialdehydes further mediate the deposition process to maintain filling ability without requiring hazardous formaldehyde.
4Shape
If copper is deposited uniformly on the inner surface of a via, then complete coverage is achieved, but the via is filled without leaving a gap making it necessary to have faster deposition near the bottom
Solution Approach 1:
The invention creates local quality variations in the deposition process by using organic compounds that preferentially adsorb on specific surfaces. The sulfonated condensates and aliphatic semialdehydes create different deposition characteristics at the via bottom versus the opening, enabling faster bottom deposition while maintaining overall via filling control and preventing opening plugging.
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 maintains a glossy plating appearance and enhances via filling ability by controlling the concentration of decomposition products, ensuring complete filling without gaps and improving thermal reliability.
Implementation Method 1
copper electroplating has rapid rates of deposition of plating films in the range of 10-50 μm/hr
Implementation Method 2
electrolysis conditions generally used direct-current electroplating using soluble anodes
Data Source
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AI summary
A copper plating solution which contains compounds with the structure -X-S-Y-where X and Y are, independently of each other, atoms selected from a group consisting of hydrogen, carbon, sulfur, nitrogen, and oxygen, and X and Y can be the same only if they are carbon atoms and aliphatic semialdehydes. By using this copper electroplating solution it is possible to form good filled vias without worsening the appearance of the plating.