Laterally Extended Conductive Bump Buffer for Copper-Gold Diffusion
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Solution Overview
Problem
Increased functional density in semiconductor devices leads to undesirable diffusion and intermixing of conductive materials like copper and gold, resulting in higher chances of failures during processing due to their reactivity and diffusion rates.
Innovation Solution
A laterally extended conductive bump buffer is implemented, using nickel as a buffer material between copper and gold, where the buffer portion is isotropically etched to be partially surrounded by the copper structure, preventing direct diffusion paths and enhancing the separation distance between materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If functional density is increased to achieve higher device density and lower cost, then productivity and production efficiency are improved, but the distance between conductive materials decreases leading to undesirable diffusion and intermixing of copper and gold
Solution Approach 1:
A nickel buffer layer is introduced between the copper interconnect and gold bump to prevent direct contact and diffusion. The nickel buffer acts as an intermediary material that blocks copper atoms from migrating into the gold, thereby maintaining material purity while allowing the device structure to achieve high functional density
Solution Approach 2:
The buffer structure extends laterally beyond the vertical interface between copper and gold, creating a three-dimensional barrier that blocks diffusion paths in multiple directions. This lateral extension adds a spatial dimension to the protection mechanism, preventing copper-gold intermixing even when vertical distance is minimized
2Device complexity
If the distance between copper and gold is decreased to increase functional density, then device complexity is reduced and production efficiency improves, but diffusion and intermixing of conductive materials increases
Solution Approach 1:
The nickel buffer layer serves as a mediating structure between copper and gold, allowing them to be positioned close together for high functional density while preventing harmful diffusion. The buffer absorbs the potential harmful interaction without requiring large separation distances
Solution Approach 2:
The interface region between copper and gold is segmented into distinct layers with nickel buffer providing a separate functional zone. This segmentation creates discrete regions with specific functions: copper for interconnect, nickel for diffusion barrier, and gold for bonding, allowing close proximity without direct interaction
3Reliability
If nickel buffer is used between copper and gold to prevent diffusion, then material purity is maintained, but the structural complexity and processing complexity increase
Solution Approach 1:
The buffer structure utilizes lateral extension beyond the vertical interface to provide diffusion protection. By extending the nickel buffer laterally, the design achieves enhanced protection with a simple planar extension rather than complex three-dimensional structures or multiple stacked layers
Solution Approach 2:
The laterally extended nickel buffer performs multiple functions simultaneously: it acts as a diffusion barrier, provides mechanical support, and creates a planar surface for subsequent processing. This multi-functionality reduces the need for additional separate structures, simplifying the overall device architecture
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 solution effectively reduces the likelihood of material adulteration and maintains the purity and conductivity of gold, thereby enhancing the reliability and performance of semiconductor devices by minimizing reactive diffusion between copper and gold.
Implementation Method 1
copper may be more reactive and diffuse more readily, relative to other materials such as nickel. Therefore, nickel may be utilized between copper and gold as a buffer to prevent the diffusion of copper into gold
Data Source
AI summary
A semiconductor device includes: a conductive structure, a conductive bump extending into the conductive structure and contacting the conductive structure along a first surface, the conductive bump configured to interface with an external semiconductor device at a second surface opposite the first surface, the conductive bump being wider along the first surface than the second surface.