Metal-Defined Pad Formation Using Excimer Laser Seed Layer Stripping
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Solution Overview
Problem
Current methods for forming metal-defined pads using wet chemistry, such as potassium cyanide, are environmentally unfriendly, limited in scalability, and result in surface finish issues like metal footing and stray plating due to limited mass transfer, which affects the performance of advanced substrate packages at higher frequencies.
Innovation Solution
Employing a low dose excimer laser beam to strip the remaining seed layer on a substrate, providing a dry, scalable, and environmentally friendly process that eliminates stray plating and surface metal foot, allowing for better performance and scalability in forming metal-defined pads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wet chemistry (potassium cyanide) is used to strip seed layer, then the seed layer can be removed, but the process is environmentally unfriendly and limited in scaling
Solution Approach 1:
The patent replaces the chemical wet etching process with a mechanical/physical laser ablation process. The laser beam directly removes the seed layer material through ablation, eliminating the need for potassium cyanide chemistry and its associated environmental harm while maintaining effective seed layer removal.
Solution Approach 2:
The patent changes the fundamental process parameter from chemical concentration and flow rate to laser power, pulse duration, and scanning speed. This parameter transformation enables scaling without the mass transfer limitations of wet chemistry while eliminating environmental contamination.
2Ease of manufacture
If wet chemistry is used for seed layer stripping, then the process can be implemented, but mass transfer is limited causing surface finish issues like metal footing and stray plating
Solution Approach 1:
The laser-based process replaces chemical mass transfer with direct optical energy delivery and physical ablation. This substitution eliminates the mass transfer limitations that cause uneven etching, metal footing, and stray plating, resulting in superior surface finish quality while maintaining ease of manufacture through a controllable physical process.
3Area of stationary object
If traditional Solder-Metal-Defined pads are used, then the socket area is larger, but the capacitance build-up increases leading to higher insertion loss
Solution Approach 1:
The patent extracts and removes the seed layer material from areas where it would otherwise remain after metal deposition. By selectively stripping the seed layer using laser ablation, the process creates precise metal-defined pad geometries with minimized socket area, thereby reducing capacitance build-up and insertion loss.
4Ease of manufacture
If wet chemistry process is used, then the current approach can be maintained, but scalability is limited and costs are high
Solution Approach 1:
The laser processing system replaces the chemical processing line with a physical ablation system that has no mass transfer limitations. This substitution enables scaling to higher production rates and larger substrate sizes without the constraints of chemistry flow and mass transfer, while maintaining process control and quality.
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 significantly reduces insertion loss by eliminating stray plating and surface metal foot, enabling the formation of metal-defined pads that meet the requirements for next-generation products with improved performance and scalability.
Implementation Method 1
scanning a laser beam across the substrate to remove the exposed portions of the seed layer
Data Source
AI summary
The present disclosure generally relates to a method. The method may include providing a substrate and forming a seed layer on the substrate. The method may further include forming a first metal layer on selected portions of the seed layer to form exposed portions of the seed layer. The method may also include scanning a laser beam across the substrate to remove the exposed portions of the seed layer to form exposed portions of the substrate.