Multi-metal connecting portion for semiconductor package reliability
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Solution Overview
Problem
Semiconductor packages face challenges in achieving reliable electrical connections between substrates and interposers while maintaining miniaturization and high functionality, as existing solutions struggle with metal diffusion and high melting point issues.
Innovation Solution
A semiconductor package design incorporating a connecting portion with a first metal layer of low melting point tin, a second metal layer of nickel for preventing metal diffusion, and a metal post of copper, which are strategically positioned and surrounded by a mold layer for effective electrical connection and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single metal layer is used for electrical connection, then the fabrication process is simple, but metal diffusion occurs and reliability is poor
Solution Approach 1:
The connecting portion is divided into three distinct metal layers (first metal layer with low melting point metal, second metal layer with diffusion barrier metal, and third metal layer with high conductivity metal) instead of using a single metal layer. This segmentation allows each layer to perform its specific function independently, preventing metal diffusion while maintaining electrical connectivity and improving overall reliability.
Solution Approach 2:
The connecting portion uses a composite structure combining three different metal materials with complementary properties: low melting point metal for easy bonding, diffusion barrier metal for preventing metal migration, and high conductivity metal for optimal electrical performance. This composite approach resolves the contradiction by integrating multiple material advantages into a single functional component.
2Strength
If high melting point metal is used for strong bonding, then bonding strength is high, but diffusion of metals occurs
Solution Approach 1:
The second metal layer consisting of diffusion barrier metal (e.g., tungsten, molybdenum, or titanium) acts as an intermediary between the first metal layer and the third metal layer. This intermediate layer prevents direct contact and diffusion between the low melting point metal and high conductivity metal, while still allowing mechanical and electrical continuity, thus eliminating metal diffusion harmful effects.
Solution Approach 2:
Different regions of the connecting portion have different material properties optimized for their specific functions: the first metal layer provides bonding capability, the second metal layer provides diffusion protection, and the third metal layer provides electrical conductivity. This local quality differentiation resolves the contradiction by ensuring that no single material needs to simultaneously provide all properties.
3Volume of moving object
If miniaturization is pursued, then device size is reduced, but electrical connection reliability becomes more difficult to maintain
Solution Approach 1:
The solution transitions from horizontal expansion to vertical integration by stacking three metal layers in the vertical dimension. This allows the connecting portion to maintain robust electrical connection properties through multiple functional layers while keeping the horizontal footprint minimal, thus supporting miniaturization without compromising reliability.
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 design enhances the reliability and efficiency of electrical connections between the substrate and interposer, simplifies the fabrication process, and maintains the miniaturization and high functionality demands of modern semiconductor packages.
Implementation Method 1
the first metal layer includes a first metal having a relatively low melting point
Implementation Method 2
the second metal layer includes a second metal for preventing diffusion of metals
Data Source
AI summary
A semiconductor package is provided. The semiconductor package includes: a substrate; a first semiconductor chip provided on an upper surface of the substrate; an interposer provided on the first semiconductor chip; a conductive pad provided on the upper surface of the substrate; and a connecting portion provided between the upper surface of the substrate and a lower surface of the interposer, wherein the connecting portion is spaced apart from the first semiconductor chip along a horizontal direction parallel to the upper surface of the substrate, and electrically connects the conductive pad and the interposer, and the connecting portion includes a first metal layer provided on the conductive pad, a second metal layer provided on the first metal layer, and a metal post provided on the second metal layer, wherein the first metal layer includes a first metal, the second metal layer includes a second metal different from the first metal, and the metal post includes a third metal different from the first metal and the second metal.