Periodic Current Reversal Copper Plating for High Aspect Ratio Vias
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Solution Overview
Problem
The challenge is to effectively fill copper in non-through holes with high aspect ratios on substrates without forming voids, which is crucial for three-dimensional assembly of semiconductor devices, as conventional copper plating methods either lead to void formation or prolonged processing times.
Innovation Solution
The method involves periodic current reversal copper plating using an acidic copper plating bath containing a copolymer of diallylamines and sulfur dioxide, with specific current densities and timing to ensure complete filling of copper in non-through holes with high aspect ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional copper plating methods are used to fill non-through holes with high aspect ratios, then copper filling can be achieved, but voids are formed in the via holes
Solution Approach 1:
The patent applies periodic current reversal plating where the current direction is periodically reversed during copper deposition. This periodic action prevents void formation by alternately depositing copper from both directions (top-down and bottom-up), ensuring complete filling of high aspect ratio via holes without trapping hollow portions that would reduce chip reliability
Solution Approach 2:
The patent changes the plating parameters by using a specific acidic copper plating bath containing a copolymer of diallylamines and sulfur dioxide, along with controlled current density and periodic current reversal. These parameter changes enable effective copper filling in via holes with aspect ratios of 5 or more while preventing void formation, thus improving both filling completeness and chip reliability
2Reliability
If current density is decreased to prevent void formation, then voids are prevented, but plating time increases significantly
Solution Approach 1:
By periodically reversing the current direction, the plating process achieves effective filling at higher current densities. The periodic reversal prevents void formation mechanismically while allowing faster deposition rates, thus maintaining reliability without sacrificing productivity
Solution Approach 2:
The patent introduces a copolymer of diallylamines and sulfur dioxide as an intermediary substance in the acidic copper plating bath. This intermediary facilitates uniform copper deposition and prevents void formation, enabling faster plating speeds while maintaining void-free filling and thus improving productivity without compromising reliability
3Productivity
If high current density is used to reduce plating time, then productivity is improved, but voids are formed in via holes
Solution Approach 1:
Periodic current reversal allows the use of high current densities for faster plating while preventing void formation. The alternating current direction ensures copper deposits from both ends of the via hole, maintaining complete filling precision even at high deposition rates, thus improving productivity without sacrificing manufacturing precision
4Adaptability or versatility
If aspect ratio of via holes is increased for three-dimensional assembly, then integration density is improved, but void formation becomes more likely
Solution Approach 1:
The periodic current reversal technique enables effective copper filling in via holes with aspect ratios of 5 or more, which are necessary for three-dimensional assembly. By alternating current direction, the method prevents void formation in these high aspect ratio structures, thus enabling advanced packaging applications while maintaining chip reliability
Solution Approach 2:
The patent modifies plating parameters including using a specialized acidic copper plating bath with copolymer additives and controlled periodic current reversal. These parameter changes enable successful filling of high aspect ratio via holes required for three-dimensional assembly without void formation, thus improving adaptability for advanced packaging while preserving reliability
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
This approach allows for efficient and timely filling of copper in conductivity-rendered non-through holes with aspect ratios of 5 or more, preventing void formation and reducing processing time, thereby enhancing the productivity and reliability of three-dimensional semiconductor assembly.
Implementation Method 1
metallizing the silicon substrate having the via hole with copper by electroplating
Implementation Method 2
periodic current reversal copper plating with an acidic copper plating bath comprising a copolymer of diallylamines and sulfur dioxide
Implementation Method 3
filling copper in the non-through hole by periodic current reversal copper plating with an acidic copper plating bath
Data Source
AI summary
There is provided a method of well filling copper in a conductivity-rendered non-through hole having an aspect ratio (depth/hole diameter) of 5 or more on a substrate in a short period of time, and the method comprises using an acidic copper plating bath comprising a water-soluble copper salt, sulfuric acid, chlorine ion, a brightener and a copolymer of diallylamines and sulfur dioxide and filling copper in the non-through hole by periodic current reversal copper plating.