Tin Electroplating Composition for Planar Solder Deposit Leveling
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Solution Overview
Problem
Existing tin or tin alloy electroplating processes struggle to achieve uniform height and planarity of solder deposits on semiconductor substrates, particularly in features of micrometer scale, often resulting in rough surfaces and voids.
Innovation Solution
An aqueous electroplating composition containing tin ions and specific α-substituted carbonyl compounds as additives, which provide improved leveling properties, ensuring a uniform and planar tin or tin alloy layer without defects, using a bath that does not include electrolytically depositable metal ions other than tin and optional alloying metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional solder electroplating baths are used to deposit small amounts of lead-free solder on copper pillars, then the solder can be deposited, but the height uniformity of solder deposits is poor and the surface morphology is rough
Solution Approach 1:
The patent introduces specific carbonyl compound additives (such as benzylidene acetone and its derivatives) into the electroplating bath to modify the deposition parameters. These additives change the electrochemical environment and adsorption characteristics on the substrate surface, enabling uniform height deposition and smooth surface morphology that cannot be achieved with conventional baths alone
Solution Approach 2:
The carbonyl compounds act as intermediary substances that mediate between the electroplating bath and the substrate surface. They adsorb onto the substrate and modify the local electrochemical conditions, facilitating uniform nucleation and growth of solder deposits while preventing rough surface formation
2Reliability
If known solder electroplating baths are used, then solder deposition is possible, but the surface morphology becomes relatively rough
Solution Approach 1:
The patent modifies the chemical composition parameters of the electroplating bath by adding specific carbonyl compounds. This changes the deposition kinetics and surface energy characteristics, transforming the rough surface morphology into a smooth one while preserving the reliable deposition capability
3Productivity
If conventional electroplating processes are used for micrometer scale features, then deposition can occur, but coplanarity and uniformity are poor
Solution Approach 1:
The carbonyl compound additives create local quality differences in the electroplating process by preferentially adsorbing on certain surface regions. This local modification of surface properties enables precise control over deposition patterns, achieving excellent coplanarity and uniformity in micrometer scale features while maintaining deposition efficiency
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 achieves better coplanarity and reduced roughness in tin or tin alloy deposits, particularly in features ranging from 1 to 200 micrometers, enhancing the uniformity and quality of solder deposits.
Implementation Method 1
at least one additive of formula L1... The additive provides improved leveling properties, ensuring a uniform and planar tin or tin alloy layer
Implementation Method 2
aqueous composition comprising tin ions... for tin or tin alloy electroplating... applying a current density to deposit a tin or tin alloy layer
Data Source
AI summary
Described herein is an aqueous composition including tin ions, optionally alloy metal ions selected from the group consisting of silver, copper, indium, and bismuth ions and at least one additive of formula L1