Electroless Plating Liquid Mixing for Stable Miniaturized Via Filling
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Solution Overview
Problem
The challenge in electroless plating processing for semiconductor wafers is the deterioration of the plating liquid due to increased activity between metal ions and reducing agents, which occurs even when stored, posing a risk before the processing is performed, especially as the area of metal wiring at the via bottom surface decreases with miniaturization.
Innovation Solution
A plating method involving the generation of a plating liquid by mixing a first chemical liquid containing metal ions and a reducing agent with a second chemical liquid having a pH adjuster as the main component, which suppresses the reaction between the metal ion and the reducing agent, thereby enhancing the activity of the plating liquid just before use and preventing deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the plating liquid is prepared in advance by mixing metal ions and reducing agents, then the processing can be performed conveniently, but the plating liquid deteriorates due to increased reaction activity
Solution Approach 1:
The plating liquid is divided into two separate chemical liquids: a first chemical liquid containing metal ions and a reducing agent, and a second chemical liquid containing a pH adjuster. These are mixed immediately before use rather than being prepared in advance, preventing deterioration while maintaining operational convenience.
Solution Approach 2:
The substrate is pre-treated with a catalyst solution before the plating liquid is applied. This preliminary action ensures the substrate is ready for plating, and the plating liquid components are only combined at the moment of application, preventing premature reaction and deterioration.
2Area of moving object
If the area of metal wiring at via bottom surface is decreased for miniaturization, then the device density is improved, but the reaction activity between metal ions and reducing agents increases causing deterioration
Solution Approach 1:
By segmenting the plating liquid into separate components (first chemical liquid with metal ions and reducing agent, second chemical liquid with pH adjuster) that are mixed only when needed, the invention prevents deterioration even as the metal wiring area decreases and reaction activity increases.
3Loss of time
If the plating liquid is stored for later use, then the processing schedule is flexible, but the reaction between metal ion and reducing agent proceeds in the stored liquid causing deterioration
Solution Approach 1:
The plating liquid components are segmented into separate storage solutions (first chemical liquid and second chemical liquid) that can be stored independently without deterioration. They are combined immediately before application, eliminating the problem of reaction during storage while maintaining scheduling flexibility.
Solution Approach 2:
The pH adjuster in the second chemical liquid acts as an intermediary that controls the reaction conditions. By adjusting the pH at the moment of mixing, it prevents premature reaction during storage while enabling the plating reaction to proceed when applied to the substrate.
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 method effectively suppresses the deterioration of the plating liquid, allowing for successful filling of miniaturized vias during electroless plating processing without voids or seams, even when the via is miniaturized, by maintaining the activity of the plating liquid within optimal levels.
Implementation Method 1
performing an electroless plating processing by using a metal wiring exposed at a bottom surface of a via as a catalyst to thereby fill an inside of the via with a metal
Implementation Method 2
generating a plating liquid by mixing a first chemical liquid containing a metal ion and a reducing agent
Data Source
AI summary
A plating method includes preparing; generating a plating liquid; and performing an electroless plating processing. In the preparing, a substrate is prepared. In the generating of the plating liquid, the plating liquid M is generated by mixing a first chemical liquid L1 containing a metal ion, a reducing agent and a complexing agent with a second chemical liquid L2 containing a pH adjuster as a main component. In the performing of the electroless plating processing, the electroless plating processing is performed on the substrate by using the generated plating liquid M immediately after the generating of the plating liquid.