Quaternized Polyethylene Imine Additive for TSV Copper Plating Void Reduction
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Solution Overview
Problem
The Through Silicon Via (TSV) copper plating process using bottom-up electroplating results in micro-voids between grain boundaries after annealing, which affects the reliability of the copper columns.
Innovation Solution
An additive containing quaternized polyethylene imine derivatives and polyethylene glycol is used in the copper methyl sulfonate electroplating solution to reduce micro-voids, with a formulation that includes specific weight percentages and molecular weights, along with accelerators and leveling agents to refine grain sizes and ensure uniform deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If bottom-up electroplating is used to fill TSV holes, then electroplating speed is maximized, but micro-voids form between grain boundaries after annealing
Solution Approach 1:
The patent changes the chemical parameters of the electroplating solution by introducing quaternized polyethylene imine derivatives and polyethylene glycol. These additives modify the deposition mechanism and grain growth characteristics, allowing rapid bottom-up plating while preventing micro-void formation through controlled grain boundary development during annealing.
Solution Approach 2:
The quaternized polyethylene imine derivatives act as intermediary substances that mediate between the copper ions and the growing copper grains. They adsorb at grain boundaries and influence the annealing process, preventing void formation while maintaining the high-speed bottom-up deposition characteristic.
2Manufacturing precision
If conformal plating is used to fill TSV holes, then plating uniformity is improved, but electroplating speed is reduced
Solution Approach 1:
The patent modifies the electroplating solution composition with specific additives that enable the plating process to achieve both conformal uniformity and high deposition speed. The quaternized polyethylene imine derivatives and polyethylene glycol work synergistically to maintain uniform grain growth while accelerating overall deposition rate.
3Strength
If annealing is performed to integrate Cu grains, then grain strength is improved, but micro-voids develop between different grains
Solution Approach 1:
The quaternized polyethylene imine derivatives serve as intermediary agents during the annealing process. They remain adsorbed at grain boundaries and facilitate controlled grain integration while preventing the formation of micro-voids, thus achieving both strong grain integration and void-free structure.
Solution Approach 2:
The additives are introduced beforehand into the electroplating solution, where they prepare the grain boundary structure in advance. During subsequent annealing, these pre-positioned additives cushion against the formation of micro-voids while allowing beneficial grain integration to occur.
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 additive enables rapid deposition with minimal micro-voids between grain boundaries after annealing, enhancing the reliability and performance of TSV copper columns by eliminating etch pits and ensuring uniform grain sizes and crystallization directions.
Implementation Method 1
the electroplating and removal of the through holes and the electroplating of the re-distribution lead (RDL)
Implementation Method 2
Annealing process is a heat treatment process for metal, which is to heat the metal to certain temperature slowly, maintain the temperature for a while and then cool the metal at the appropriate speed
Data Source
AI summary
An additive for reducing voids after annealing of copper plating with through silicon via. The additive contains by weight percent: 0.05-1% of one or more of quaternized polyethylene imine and derivatives thereof having different molecular weights, and 1-10% of polyethylene glycol with an average molecular weight of 200-20000. The additive is used in combination with an electroplating solution of a copper methyl sulfonate system. The electroplating solution of a copper methyl sulfonate system contains 1-5 ml/L of the additive by volume ratio. The electroplating solution of a copper methyl sulfonate system contains by mass volume ratio: 50-110 g/L of copper ions, 5-50 g/L of methanesulfonic acid and 20-80 mg/L of chlorine ions. The electroplating solution also contains by volume ratio: 0.5-5 ml/L of accelerator, 5-20 ml/L of inhibitor and 5-10 ml/L of levelling agent. The additive for reducing voids after annealing of copper plating with through silicon via provided in the present invention can solve the problem of micro-voids between grain boundaries after high temperature annealing of copper plating.