Wiring Board Diffusion Suppression for Resistance Stability
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Solution Overview
Problem
Wiring boards with barrier metal layers, such as Ni—P, experience increased wiring resistance due to thermal diffusion between metal components and oxide film growth, leading to reliability issues, especially in high-temperature and high-humidity environments, and reduced wiring width exacerbates these problems.
Innovation Solution
A wiring board structure comprising a wiring layer, a diffusion suppressing layer, a base metal layer, and a passivation layer is introduced, where the diffusion suppressing layer prevents metal component diffusion, the base metal layer enhances strength, and the passivation layer maintains stability, forming a robust barrier metal layer to suppress resistance increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a barrier metal layer of related art (such as Ni-P or Ni-B plating film) is used, then the wiring board can be manufactured with standard processes, but the wiring resistance increases due to thermal diffusion and oxide film growth when heated, reducing reliability
Solution Approach 1:
The barrier metal layer is segmented into multiple distinct layers: a diffusion preventing layer (first barrier metal layer) that suppresses metal component diffusion, and a separate oxide film thickness controlling layer (second barrier metal layer) that prevents excessive oxide growth. This segmentation allows each layer to specialize in one function, resolving the contradiction between preventing diffusion and controlling oxidation that plagues single-layer barrier metals.
Solution Approach 2:
The invention uses a composite barrier metal layer structure combining different metal materials with complementary properties. The diffusion preventing layer uses metals with low diffusion rates (such as Pd, Pt, Rh, Ir, Ru, or their alloys), while the oxide film controlling layer uses metals that form stable, thin oxide films. This composite approach overcomes the limitations of single-material barrier layers that must compromise between diffusion prevention and oxidation control.
2Productivity
If the wiring width is reduced to increase functional density, then the semiconductor device becomes more highly functional, but the wiring resistance increases more significantly due to thermal diffusion and oxidation
Solution Approach 1:
By segmenting the barrier metal layer into specialized sub-layers, the invention provides enhanced protection for fine wiring lines. The diffusion preventing layer with its low-diffusion metals creates a more effective barrier against metal loss, while the oxide film controlling layer ensures minimal oxide growth even in the confined space of narrow wiring. This allows wiring widths to be reduced for higher density without the same degree of resistance increase.
3Device complexity
If a single-layer barrier metal is used to simplify the structure, then the manufacturing process is simpler, but it cannot simultaneously prevent metal diffusion and control oxide film growth effectively
Solution Approach 1:
The barrier metal layer is divided into functionally distinct segments: a diffusion preventing layer and an oxide film controlling layer. Each segment is optimized for its specific function, allowing the structure to achieve superior resistance stability under heat despite the increased layer count. The segmentation resolves the contradiction by distributing functions across specialized layers rather than requiring a single layer to perform all functions imperfectly.
Solution Approach 2:
The invention changes the material parameters of each barrier metal layer to optimize specific functions. The diffusion preventing layer uses metals with specifically selected low diffusion coefficients, while the oxide film controlling layer uses metals that form oxides with controlled growth rates and thicknesses. These parameter changes in each layer enable the composite structure to achieve reliability that exceeds the sum of its parts.
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 configuration effectively suppresses thermal diffusion and oxide film growth, maintaining low wiring resistance and ensuring high reliability even at reduced wiring widths and in harsh environmental conditions.
Implementation Method 1
suppresses diffusion of a metal component of the wiring layer
Implementation Method 2
suppress thermal diffusion and disappearance of a metal component of the wiring layer into the resin layer due to heating
Data Source
AI summary
A wiring board includes a wiring layer; a diffusion suppressing layer that covers the wiring layer and suppresses diffusion of a metal component of the wiring layer; a base metal layer that covers the diffusion suppressing layer; and a passivation layer that covers the base metal layer.