Structured Aluminum Metallization for Reliable Al-Cu Bonding
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Solution Overview
Problem
Current interconnection technologies face challenges with poor adhesive strength between aluminum (Al) and copper (Cu) interfaces, as well as between Al and epoxy-based encapsulating materials, leading to unreliable bonds and potential electrical breakdown in power electronic devices due to thermomechanical stresses and oxidation issues.
Innovation Solution
A structured aluminum metallization surface with peaks occupying 20-80% of the surface area is introduced, forming an interlock structure that enhances shear adhesive strength and reliability by distributing stress away from the interface, allowing for improved bonding with copper layers or epoxy-based encapsulants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a flat aluminum metallization surface is used, then the manufacturing process is simple and standard, but the adhesive strength between Al and Cu interfaces is poor
Solution Approach 1:
The patent applies surface curvaturization by creating a structured metallization surface with peaks and valleys instead of a flat surface. The peaks occupy 20-80% of the surface area and have heights of 1-10 μm, creating a three-dimensional topography that mechanically interlocks with deposited copper layers and encapsulants, thereby significantly improving adhesive strength.
Solution Approach 2:
The invention transitions from a two-dimensional flat surface to a three-dimensional structured surface by adding vertical dimension with peaks extending 1-10 μm above the base plane. This dimensional change creates mechanical interlocking features that enhance bonding without requiring additional bonding layers or complex assembly processes.
2Reliability
If a flat aluminum metallization surface is used, then the manufacturing process is simple, but the reliability under thermomechanical stresses is poor
Solution Approach 1:
The structured surface with peaks and valleys creates a three-dimensional topography that distributes thermomechanical stresses more evenly across the bonding interface. The curved surfaces of the peaks reduce stress concentration points compared to sharp edges, improving bond reliability under thermal cycling and mechanical loading conditions.
Solution Approach 2:
The patent creates localized regions of enhanced bonding strength by forming peaks at specific locations on the metallization surface. The peaks occupy 20-80% of the surface area, creating localized interlocking features that provide superior stress distribution and bond reliability in critical bonding regions while maintaining overall structural integrity.
3Strength
If a flat aluminum metallization surface is used, then the manufacturing process is simple and fast, but the adhesive strength between Al and epoxy encapsulant is poor
Solution Approach 1:
The three-dimensional peak structure creates mechanical interlocking with the epoxy encapsulant during the encapsulation process. The curved surfaces allow better epoxy penetration and wetting into the peak valleys, creating strong mechanical anchoring without requiring additional surface treatment steps or extended processing times.
Solution Approach 2:
The metallization surface is pre-structured with peaks before the copper deposition and encapsulation steps. This preliminary structuring creates built-in mechanical interlocking features that enhance bonding during subsequent manufacturing steps, eliminating the need for additional surface preparation or bonding enhancement processes.
4Manufacturing precision
If the peak structure occupies small area percentage, then the manufacturing precision requirement is lower, but the stress distribution effect is insufficient
Solution Approach 1:
The patent defines specific parameter ranges for the peak structure: peak height of 1-10 μm, peak spacing of 5-50 μm, and peak area percentage of 20-80%. These parameter specifications provide clear manufacturing targets that balance ease of fabrication with effective stress distribution, allowing standard manufacturing processes to achieve the desired 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 structured aluminum surface increases the reliability of Al-Cu interfaces and Al-epoxy bonds, reducing the risk of adhesive failure and enhancing the overall performance and longevity of power electronic devices by distributing shear stresses and improving physical bonding within the bulk material.
Implementation Method 1
A structured aluminum metallization surface with peaks occupying 20-80% of the surface area is introduced, forming an interlock structure that enhances shear adhesive strength
Implementation Method 2
forming an interlock structure that enhances shear adhesive strength and reliability by distributing stress away from the interface
Data Source
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AI summary
The present disclosure relates to a semiconductor chip, having an aluminium layer, wherein said aluminium layer has a structuration of at least a portion of a surface receiving an additional deposition (Cu), and wherein said structuration forms peaks on said portion of surface occupying between 20 and 80% of said portion of surface.