Tin Electroplating Composition for Smooth, Uniform Solder Deposits
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Solution Overview
Problem
The electronics industry faces challenges in achieving uniform and smooth tin or tin alloy electroplating deposits with low roughness and voids, particularly for features in the micrometer scale, which is crucial for increasing connection density on semiconductor substrates.
Innovation Solution
An aqueous composition containing specific suppressing agents, derived from polyamine starters reacted with alkylene oxides, is used in the electroplating process to inhibit dendrite growth and achieve smoother surfaces and improved coplanarity, allowing for uniform deposition on features from 500 nanometers to 500 micrometers in size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional solder electroplating baths are used, then solder can be deposited on copper pillars, but the deposited solder has rough surface morphology and non-uniform height
Solution Approach 1:
The patent applies parameter changes by introducing specific suppressing agents (surfactants) into the electroplating bath to modify the deposition parameters. These surfactants change the interfacial properties and deposition kinetics, enabling control over grain growth and surface morphology. The specific parameters modified include surface tension, deposition rate uniformity, and nucleation density, which collectively achieve smooth surfaces and uniform heights
Solution Approach 2:
The patent uses suppressing agents as intermediary substances that mediate between the electroplating bath and the substrate surface. These surfactants act as intermediaries that adsorb at the electrode-electrolyte interface, modifying the deposition process to prevent dendrite formation and promote uniform growth. The intermediaries control the interaction between metal ions and the substrate, achieving the desired surface quality
2Shape
If suppressing agents are added to improve surface morphology, then surface roughness decreases, but it becomes challenging to achieve uniform deposition height across micrometer-scale features
Solution Approach 1:
The patent modifies deposition parameters by controlling the concentration and type of suppressing agents, along with adjusting electrolyte composition and deposition conditions. These parameter changes enable simultaneous achievement of smooth surfaces and uniform heights by optimizing the balance between suppression and deposition rates across different feature sizes
Solution Approach 2:
The patent applies local quality by using suppressing agents that exhibit selective adsorption behavior on different surface features. The surfactants preferentially adsorb on protruding regions and high-curvature areas, providing localized suppression where needed most. This enables uniform deposition across micrometer-scale features while maintaining smooth surfaces, as the suppressing agents act differently on various local geometries
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 use of these suppressing agents results in tin or tin alloy deposits with reduced roughness and improved uniformity, effectively filling features without forming significant voids, enhancing the connection density and surface quality on semiconductor substrates.
Implementation Method 1
suppressing agents, also often referred to as surfactants
Implementation Method 2
tin or tin alloy electroplating compositions
Data Source
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AI summary
The present invention provides an aqueous composition comprising tin ions and at least one compound of formula I wherein X1 is selected from a linear or branched C1-C12 alkanediyl, which may optionally be interrupted by O or S or a C5 to C12 aromatic moiety, R11 is a copolymer of ethylene oxide and a further C3 to C6 alkylene oxide, wherein the content of ethylene oxide is from 5 to 30 % by weight, R12 is selected from H, R11, R40, R13, R14 are (a) independently selected from H, R11, R40, or (b) may together form a divalent group X13; X13 is selected from a linear or branched C1-C12 alkanediyl, which may optionally be interrupted by O, S or NR43; R40 is H or a linear or branched C1-C20 alkyl, R43 is selected from H, R11 and a linear or branched C1-C20 alkyl.