Cobalt Electroplating Composition for Uniform Void-Free Feature Filling

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Solution Overview

Problem

Existing cobalt electroplating baths exhibit pronounced non-uniformity and non-conformity in depositing cobalt layers, particularly in submicrometer-sized interconnects and micrometer-sized solder bump features, leading to voids and seams, and there is a need for a boric acid-free composition that ensures uniformity and void-free filling.

Innovation Solution

A cobalt electroplating composition using ammonium compounds, suppressing agents, and leveling agents to improve uniformity and avoid boric acid, which includes specific ammonium compounds and additives to enhance deposition uniformity across the wafer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If conventional electroplating compositions are used, then plating operation is maintained, but bath stability deteriorates due to metal particle formation and organic decomposition

Engineering Contradiction:

Improvebath stabilityVSAvoidplating operation consistency

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

The patent changes the chemical parameters of the electrolyte by introducing a nitrate salt and a carboxylic acid with specific structural features (alpha-substitution with electron-withdrawing groups). These parameter changes prevent metal particle formation and organic decomposition, thereby maintaining both bath stability and plating operation consistency over extended periods.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The carboxylic acid component acts as an intermediary substance that mediates between the cobalt ions and the electrolyte environment. Its specific molecular structure with electron-withdrawing groups allows it to stabilize the plating solution by preventing unwanted side reactions, thus maintaining reliability without sacrificing operational continuity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If plating solution is not filtered frequently, then productivity is maintained, but manufacturing precision deteriorates due to metal particles on substrate

Engineering Contradiction:

Improveplating production rateVSAvoidsubstrate surface quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent converts the potentially harmful effect of metal particle formation into a beneficial outcome by using controlled particle precipitation. The added nitrate salt and carboxylic acid cause unwanted metal particles to precipitate out in a controlled manner, which can then be removed through less frequent filtration, thereby maintaining productivity while improving surface quality.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

By changing the chemical composition parameters (adding nitrate salt and specific carboxylic acid), the patent alters the precipitation behavior of metal particles. This allows particles to be controlled and managed more effectively, reducing the frequency of filtration needed while maintaining high substrate surface quality standards.

Inventive Principle:

Principle #35Parameter changes

3Strength

If cobalt content is increased to improve coating properties, then strength is improved, but loss of substance increases due to higher cobalt salt consumption

Engineering Contradiction:

Improvecoating strengthVSAvoidcobalt salt consumption

Core Design Contradiction:

StrengthVSLoss of substance

Solution Approach 1:

The patent optimizes the concentration parameters of cobalt salts in the electrolyte by introducing efficiency-enhancing components (nitrate salt and carboxylic acid). These components improve the utilization efficiency of cobalt ions, allowing achieving the same coating strength with lower cobalt salt consumption, thus reducing substance loss while maintaining coating quality.

Inventive Principle:

Principle #35Parameter changes

4Productivity

If plating bath is operated for extended periods, then productivity is improved, but manufacturing precision deteriorates due to bath decomposition

Engineering Contradiction:

Improvecontinuous plating outputVSAvoidcoating quality consistency

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies a controlled excess of stabilizing agents (nitrate salt and carboxylic acid) to prevent decomposition during extended operation. This partial excessive action ensures that even during prolonged continuous plating, the bath maintains its chemical stability and produces consistent coating quality, enabling extended operation without sacrificing manufacturing precision.

Inventive Principle:

Principle #16Partial or excessive action

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 composition significantly reduces non-uniformity of cobalt deposits, achieving a substantially planar surface and void-free filling of features, while being environmentally friendly by eliminating boric acid.

Implementation Method 1

Composition for cobalt or cobalt alloy electroplating

Methodology Applied

Scientific EffectElectroplating: Electroplating

Implementation Method 2

cobalt or cobalt alloy electroplating

Methodology Applied

Scientific EffectElectrochemical reduction: Electrolysis

Data Source

PatentEP3781728B1Composition for cobalt or cobalt alloy electroplating

Publication Date: 2026.05.06 BASF SE

AI summary

A cobalt electroplating composition comprising: (a) cobalt ions, (b) an ammonium compound of formula (NR1R2R3H+)nXn- wherein R1, R2, R3 are independently selected from H and linear or branched C1 to C6 alkyl, X is selected from an n valent inorganic or organic counter ion, n is an integer selected from 1, 2 or 3.