Sintered Copper Pillar Bump Adhesion on Aluminum Pads
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bumping techniques face reliability issues due to stress concentration and electro-migration when sintered pillar bumps are formed on contact pads made of different conductive materials, particularly aluminum, as adhesion between the pillar and the pad is degraded even after surface oxide removal.
Innovation Solution
A method involving the preparation of a substrate with pads coated with a metallic adhesion layer, followed by sintering conductive particles to form a bump base and filling the remaining space with solder material, ensuring tight bonding between the sintered bumps and pads of different conductive materials without requiring high-temperature processes or expensive plating techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sintered copper pillar bumps are formed on aluminum contact pads, then cost is reduced by avoiding expensive plating processes, but adhesion between the pillar and pad is degraded
Solution Approach 1:
The patent introduces a metallic adhesion layer as an intermediary between the sintered copper pillar bump and the aluminum contact pad. This adhesion layer serves as a mediator that chemically bonds to both the copper particles and the aluminum pad, resolving the adhesion incompatibility between dissimilar conductive materials while maintaining the cost advantage of sintering over plating
Solution Approach 2:
The patent creates a composite structure consisting of multiple materials: the sintered copper pillar bump, the metallic adhesion layer, and the aluminum contact pad. This composite approach allows each material to perform its optimal function - copper provides conductivity and structural integrity, the adhesion layer provides bonding, and aluminum provides the contact interface - thereby solving the adhesion problem while maintaining manufacturing efficiency
2Reliability
If surface oxide of aluminum pads is removed before bump formation, then adhesion is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent applies the metallic adhesion layer to the aluminum pad surface before forming the sintered copper pillar bumps. This preliminary action of coating the adhesion layer in advance ensures that the surface is pre-prepared for optimal bonding, and the sintering process itself provides the necessary heating to facilitate adhesion without requiring separate high-temperature oxide removal steps
3Productivity
If bump pitch and bump size become fine for high-density interconnect, then signal transmission performance is improved, but stress concentration and electro-migration reliability issues arise
Solution Approach 1:
The patent changes the material parameters of the bump structure by using sintered copper particles with controlled size distribution and density, combined with an optimized metallic adhesion layer composition. These parameter changes enable fine pitch and fine size bumps to achieve sufficient mechanical strength and stress resistance while maintaining the high-density interconnect configuration
Solution Approach 2:
The composite structure of sintered copper particles with the metallic adhesion layer creates a more robust connection interface that better distributes stress and resists electro-migration effects. This composite approach allows fine-pitch bumps to maintain reliability by combining the high conductivity of copper with the strong bonding capability of the adhesion layer
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 approach enables robust bonding of sintered bumps to pads of varying conductive materials, enhancing reliability and preventing semiconductor device degradation, while avoiding costly plating processes and high-temperature conditions.
Implementation Method 1
coating a metallic adhesion layer on each pad... enables fabrication of a bump structure including a set of bumps on a substrate, in which the bumps made by sintering the conductive particles are tightly bonded to pads of the substrate
Implementation Method 2
forming a bump on each pad by sintering conductive particles using a mold layer, in which the conductive particles includes second conductive material different from the first conductive material
Data Source
AI summary
A technique for fabricating a bump structure is disclosed. A substrate that includes a set of pads formed on a surface thereof is prepared, in which the pads includes first conductive material. A metallic adhesion layer is coated on each pad. A bump base is formed on each pad by sintering conductive particles using a mold layer, in which the conductive particles includes second conductive material different from the first conductive material.