Tin Alloy Plating Solution for Uniform Bump Height
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Solution Overview
Problem
Existing tin or tin alloy plating solutions struggle to achieve uniform height among bumps with different diameters during the electroplating process, leading to height variations in solder bumps formed on semiconductor wafers.
Innovation Solution
A tin or tin alloy plating solution comprising a stannous salt, an organic or inorganic acid, a nonionic surfactant, benzalacetone, and a solvent, where benzalacetone is included in the range of 0.05 g/L to 0.2 g/L, and the surfactant to benzalacetone mass ratio is between 10 to 200, and the solvent to benzalacetone mass ratio is 10 or more, to control the deposition and ensure uniform film thickness across varying via diameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional tin or tin alloy plating solutions are used, then electroplating can be performed, but height variation among bumps with different diameters occurs
Solution Approach 1:
The patent changes the chemical parameters of the plating solution by adding benzalacetone at a specific concentration (0.01-10 g/L) and controlling the mass ratio of nonionic surfactant to benzalacetone (10-200). These parameter changes modify the deposition behavior of tin metal to achieve uniform bump heights across different via diameters. The specific concentration ranges and ratios are optimized to control the plating rate and deposition uniformity.
Solution Approach 2:
Benzalacetone acts as an intermediary substance between the nonionic surfactant and the tin metal deposition process. It mediates the interaction by adsorbing onto the via surface and modifying how the surfactant influences metal precipitation. This intermediary effect allows for controlled, uniform deposition across varying via geometries by regulating the interfacial interactions during electroplating.
2Reliability
If metal precipitation is suppressed in the upper portion of via, then void-free filling is achieved, but control over deposition uniformity across different via sizes becomes difficult
Solution Approach 1:
The patent applies local quality by having the nonionic surfactant and benzalacetone concentrate preferentially in the upper portion of the via during electroplating. This localized concentration creates a spatial gradient where metal precipitation is suppressed at the top (preventing voids) while allowing controlled deposition at the bottom and sides. The local chemical environment is optimized to achieve both void-free filling and uniform deposition simultaneously.
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 suppresses tin precipitation, resulting in void-free bumps with a height variation of 10% or less, even in patterns with different bump diameters, enhancing the reliability of semiconductor devices by ensuring uniform bump height and appearance.
Implementation Method 1
the benzalacetone (D) is included in the plating solution in an amount of 0.05 g/L to 0.2 g/L... effectively suppresses tin precipitation
Implementation Method 2
forming a tin or tin alloy-plated film using an electroplating method
Data Source
AI summary
This tin or tin alloy plating solution includes a soluble salt including at least a stannous salt (A), an acid selected from an organic acid and an inorganic acid or a salt thereof (B), a surfactant (C), benzalacetone (D), and a solvent (E), wherein the plating solution is used to form a pattern in which bump diameters are different from each other on a base material, an amount of the benzalacetone (D) is 0.05 g/L to 0.2 g/L, a mass ratio (C/D) of the surfactant (C) to the benzalacetone (D) is 10 to 200, and a mass ratio (E/D) of the solvent (E) to the benzalacetone (D) is 10 or more.