Semiconductor Package Conductive Cap Shear Strength
Solution Overview
Problem
The copper-to-copper bonding technique faces challenges in enhancing the bonding force of the bonding structure, which affects the shear strength at the interface between bonded layers.
Innovation Solution
A conductive cap with greater hardness is applied to the top and side surfaces of a conductive layer, enhancing the shear strength by forming a stronger interface with another conductive layer, and the cap layer is designed to have grains of a third average size smaller than both the first and second conductive layers, improving bonding force through grain size differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper-to-copper bonding technique is used to avoid solder material and intermetallic compound formation, then reliability is improved, but bonding force at the interface is insufficient
Solution Approach 1:
The patent changes the hardness parameter of the conductive layer by forming a cap layer with different material composition or microstructure. This parameter change enables the conductive layer to achieve both good bonding reliability (avoiding solder and IMC) and sufficient bonding force (through enhanced hardness of the cap layer).
Solution Approach 2:
The patent creates a composite structure by forming a cap layer on top of the copper conductive layer. The cap layer may have different material properties (higher hardness) while maintaining electrical conductivity, thus combining the advantages of solder-free bonding with enhanced mechanical strength at the interface.
2Strength
If a conductive cap with greater hardness is applied to the conductive layer, then shear strength at the interface is improved, but device complexity increases
Solution Approach 1:
The conductive layer is segmented into two distinct parts: the base copper layer and the cap layer. This segmentation allows each part to have optimized properties - the base layer provides electrical conductivity and the cap layer provides enhanced hardness and shear strength, thereby resolving the contradiction between improved strength and increased complexity.
Solution Approach 2:
The cap layer is applied locally to specific regions of the conductive layer where bonding occurs. This local quality enhancement means that the increased complexity is confined to the bonding interface areas, while the rest of the device maintains its original simple structure.
Data Source
AI summary
A semiconductor package includes an electrical connection structure. The electrical connection structure includes: a first conductive layer; a second conductive layer on the first conductive layer; and a conductive cap between the first conductive layer and the second conductive layer, the conductive cap having a hardness greater than a hardness of the first conductive layer.