Through-Hole Substrate Metallization for High-Aspect-Ratio Coverage
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Solution Overview
Problem
The issue of low step coverage and increased process defects in forming metal layers on inorganic substrates using dry deposition methods, particularly for blind vias and through-holes with high aspect ratios, leads to reduced product reliability.
Innovation Solution
A substrate structure and manufacturing method involving a core substrate with a sputtered metal layer formed through a dry process, followed by an electroless metal layer formed through a wet process, and a conductive material layer to fill through-holes, optionally with an adhesion promotion layer to enhance adhesion, addressing low step coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dry deposition methods (PVD or CVD) are used to form metal layers on inorganic substrates, then adhesion between inorganic substrates and metal layers is achieved, but step coverage is low for blind vias and through-holes with high aspect ratios
Solution Approach 1:
The metal layer formation process is segmented into multiple stages: first forming a seed layer via dry deposition, then completing the fill via electroplating. This segmentation allows each process to optimize for its specific function - the seed layer provides adhesion and nucleation sites, while the electroplating process provides excellent step coverage and fill capability for high aspect ratio structures
Solution Approach 2:
A seed layer acts as an intermediary between the inorganic substrate and the final metal fill. This intermediate layer facilitates both adhesion (solving the reliability issue) and provides a foundation for electroplating that achieves excellent step coverage (solving the manufacturing precision issue)
2Ease of manufacture
If dry deposition methods are used to form metal layers, then metal layers can be deposited on inorganic substrates, but process defects increase and product reliability reduces
Solution Approach 1:
The invention changes the process parameters by transitioning from a single dry deposition process to a hybrid process combining dry deposition (for seed layer) and wet electroplating (for final fill). This parameter change in the manufacturing process reduces defects and improves reliability while maintaining the ability to deposit metal layers on inorganic substrates
3Manufacturing precision
If electroless metal layer is formed on remaining portion of inner wall, then coverage is improved, but process complexity increases
Solution Approach 1:
The metal deposition is segmented into distinct zones: dry deposition forms the seed layer on accessible surfaces, while electroless metal layer completes the coverage on remaining inner wall portions. This segmentation achieves comprehensive coverage while using specialized processes only where needed, balancing complexity and performance
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 improves structural reliability by enhancing adhesion and coverage, reducing process defects and increasing the reliability of the substrate structure.
Implementation Method 1
The sputtered metal layer is configured on the upper surface, the lower surface, and a portion of an inner wall of the at least one through-hole of the core substrate
Implementation Method 2
The electroless metal layer is configured on the sputtered metal layer and a remaining portion of the inner wall of the at least one through-hole
Implementation Method 3
an adhesion promotion layer, directly covering the upper surface, the lower surface, and the inner wall of the at least one through-hole of the core substrate
Data Source
AI summary
A substrate structure, including a core substrate, a sputtered metal layer, an electroless metal layer, and a conductive material layer. The core substrate has an upper surface, a lower surface, and at least one through-hole penetrating from the upper surface to the lower surface. The sputtered metal layer is configured on the upper surface, the lower surface, and a portion of an inner wall of the through-hole of the core substrate. The electroless metal layer is configured on the sputtered metal layer and a remaining portion of the inner wall of the through-hole. The conductive material layer is configured on the electroless metal layer and fills the through-hole to define at least one first conductive circuit on the upper surface, at least one second conductive circuit on the lower surface, and at least one conductive through-hole located in the through-hole and electrically connected to the first and second conductive circuits.