Fine Redistribution Interconnects With Molybdenum for Sub-Micron RDL
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Solution Overview
Problem
Current high-density redistribution line technologies in the packaging industry face challenges in achieving sub-micron line/space resolution, are cost-inefficient, and have high RF insertion loss, making them unsuitable for large-scale production and future resolution trends.
Innovation Solution
A method utilizing a molybdenum adhesion layer with a copper seed layer and photoresist patterning, followed by copper plating, etching, and adhesion layer removal, enables the production of electrical components with sub-micron line/space resolution, minimizing undercut and surface leakage, and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional redistribution layer technologies are used, then production cost is reduced, but manufacturing precision deteriorates (cannot achieve sub-micron line/space resolution)
Solution Approach 1:
The patent changes the material parameter of the adhesion layer from conventional materials (Ti, W, Pt) to molybdenum, which has specific etching selectivity properties that enable sub-micron resolution. This material parameter change allows the etching process to stop precisely at the desired depth without undercut, achieving L/S 1μm/1μm resolution while using standard manufacturing processes
Solution Approach 2:
The patent uses a disposable photoresist pattern that is removed after defining the copper trace geometry. This allows precise sub-micron patterning without requiring expensive reusable masks or complex alignment systems, achieving high resolution at low cost
2Manufacturing precision
If silicon interposer technology is used, then manufacturing precision is improved, but device complexity increases and RF insertion loss increases
Solution Approach 1:
The patent copies the successful semiconductor fabrication process flow (spin-on dielectric, photoresist patterning, copper plating, etching) onto organic substrates. This allows sub-micron resolution to be achieved using familiar, low-complexity processes rather than requiring specialized silicon interposer platforms
Solution Approach 2:
The patent creates a universal fabrication process that works on both organic and inorganic substrates. The same process flow achieves sub-micron resolution regardless of substrate type, eliminating the need for platform-specific processes and reducing overall device complexity
3Ease of manufacture
If embedded copper trace technology is used, then production cost is reduced, but productivity deteriorates due to additional steps
Solution Approach 1:
The patent extracts and eliminates the CMP step from the conventional embedded copper trace process. By using molybdenum adhesion layer with high etching selectivity, the process achieves precise copper trace formation without requiring copper overburden removal, reducing production steps and increasing productivity
Solution Approach 2:
The patent performs preliminary action by carefully controlling the etching depth to stop precisely at the adhesion layer interface. This preliminary precision in etching depth control eliminates the need for subsequent CMP processing, reducing overall production time while maintaining cost effectiveness
4Manufacturing precision
If photoresist patterning with copper plating is used, then manufacturing precision is improved, but object-generated harmful factors increase due to undercut formation
Solution Approach 1:
The patent changes the etching parameter by selecting molybdenum adhesion layer which has high etching selectivity and forms a clean stopping interface. This parameter change prevents undercut formation during etching, achieving sub-micron resolution without the harmful undercut effect that plagues conventional processes
Solution Approach 2:
The molybdenum adhesion layer serves as an intermediary between the copper trace and the underlying substrate. This intermediary layer provides a sharp etching stop interface that prevents the etchant from attacking the substrate, eliminating undercut while enabling precise sub-micron copper trace formation
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 method achieves sub-micron line/space resolution with improved electrical performance, reduced production time, and lower costs, suitable for large-scale manufacturing, while avoiding issues like undercut and surface leakage.
Implementation Method 1
coating at least one side of the polyimide substrate with an adhesion layer comprising molybdenum
Implementation Method 2
covering at least a portion of the copper seed layer with a coating of photoresist; removing a section of the coating of the photoresist to produce a surface feature
Implementation Method 3
performing a copper plating process wherein the surface feature is filled with copper
Implementation Method 4
performing a copper etching on the copper surface to produce copper etched surface and performing an adhesion layer etching on the copper etched surface
Data Source
Figure 1
Figure 2A~2F
Figure 3A~3F
AI summary
A method for producing an electrical component is disclosed using a molybdenum adhesion layer, connecting a polyimide substrate to a copper seed layer and copper plated attachment.