NiAu Bump Barrier Layer Copper Diffusion
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Solution Overview
Problem
Copper from copper pads diffuses to the gold layer in nickel/gold (Ni/Au) bumps during high-temperature processes in wafer-level packaging, leading to contamination, increased contact resistance, and reduced bondability, resulting in low yields during the bulk manufacture and packaging of integrated circuits.
Innovation Solution
A bump structure with a barrier layer is introduced, which blocks the diffusion of copper from the pad to the gold layer along the sidewalls of the nickel layer, using materials like titanium nitride or tantalum nitride to prevent contamination and maintain low contact resistance and high bondability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-temperature processes are used in wafer-level packaging, then packaging efficiency and productivity are improved, but copper diffusion to the gold layer occurs causing contamination and reduced bondability
Solution Approach 1:
A barrier layer comprising titanium nitride or tantalum nitride is introduced between the copper pad and the gold layer in the Ni/Au bump structure. This intermediary layer effectively blocks copper diffusion to the gold layer during high-temperature packaging processes, preventing contamination while maintaining process efficiency and bondability.
2Ease of manufacture
If nickel/gold bumping is performed without a barrier layer, then the manufacturing process is simpler and more straightforward, but copper diffusion increases contact resistance and reduces yield
Solution Approach 1:
The barrier layer serves as a thin intermediary film that blocks copper diffusion pathways. Although it adds a step to the manufacturing process, it dramatically improves yield by preventing contact resistance issues and bondability problems, making the overall process more reliable and efficient.
3Object-affected harmful factors
If the barrier layer is made thicker to better block copper diffusion, then copper contamination is reduced, but the contact resistance may increase and manufacturing complexity increases
Solution Approach 1:
The barrier layer thickness is optimized to a specific range (typically 50-200 nanometers) to achieve effective copper diffusion blocking while maintaining low contact resistance. This parameter optimization ensures sufficient barrier performance without excessive thickness that would increase resistance or manufacturing difficulty.
Solution Approach 2:
The barrier layer uses specific materials (titanium nitride or tantalum nitride) that provide excellent copper diffusion blocking properties with good electrical conductivity. These composite material properties allow thin layer thickness to achieve both contamination prevention and low contact resistance simultaneously.
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 barrier layer effectively prevents copper diffusion, ensuring low contact resistance and high bondability of the Ni/Au bumps to benzocyclobutene, thereby improving yields in the bulk manufacture and packaging of integrated circuits.
Implementation Method 1
Copper from copper pads diffuses to the gold layer in nickel/gold (Ni/Au) bumps during high-temperature processes
Data Source
AI summary
A bump structure with a barrier layer, and a method for manufacturing the bump structure, are provided. In some embodiments, the bump structure comprises a conductive pad, a conductive bump, and a barrier layer. The conductive pad comprises a pad material. The conductive bump overlies the conductive pad, and comprises a lower bump layer and an upper bump layer covering the lower bump layer. The barrier layer is configured to block movement of the pad material from the conductive pad to the upper bump layer along sidewalls of the lower bump layer. In some embodiments, the barrier layer is a spacer lining the sidewalls of the lower bump layer. In other embodiments, the barrier layer is between the barrier layer and the conductive pad, and spaces the sidewalls of the lower bump layer from the conductive pad.