Multi-Layer Interconnect Pillars for Dense, Low-Stress IC Connections
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Solution Overview
Problem
The increasing complexity of integrated circuits in modern electronic devices poses challenges in forming reliable and densely packed interconnects due to limited space, leading to issues with conventional solder bumps and copper posts, which can cause short circuits and stress-related damage.
Innovation Solution
The use of multi-layer interconnect pillars with alternating reinforcement and solder layers provides a dimensionally stable and compliant solution for electrical interconnections, allowing for close packing without causing short circuits and reducing stress on the devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solder bumps are used for interconnection, then electrical connections can be established, but short circuits occur due to spreading and stress-related damage
Solution Approach 1:
The interconnect structure is divided into multiple functional layers: a rigid base layer for dimensional stability, a compliant intermediate solder layer for stress absorption, and a cap layer for electrical connection. This segmentation allows each layer to perform its specific function without causing short circuits or stress damage.
Solution Approach 2:
The invention uses a composite interconnect structure combining materials with different mechanical properties - a rigid base material (e.g., copper or tungsten pillar) combined with a compliant solder material. This composite approach provides both dimensional stability and stress compliance, preventing short circuits while maintaining reliable electrical connections.
2Productivity
If interconnect spacing is reduced to increase density, then more connections can be formed in limited space, but short circuits occur between adjacent interconnects
Solution Approach 1:
The interconnect is segmented into a rigid base portion that maintains precise spacing and a compliant solder portion that is contained within a recess. This segmentation prevents the solder from spreading laterally and causing short circuits between densely packed interconnects while still allowing sufficient electrical connection.
Solution Approach 2:
The invention transitions from a traditional planar interconnect to a three-dimensional structure with a recessed solder region. By confining the compliant solder material in the vertical dimension (within the recess), the design enables closer horizontal spacing without increasing the risk of lateral spreading and short circuits.
3Stability of the object's composition
If rigid interconnect structures are used, then dimensional stability is maintained, but stress-related damage occurs to the device
Solution Approach 1:
The interconnect is divided into a rigid base layer that provides dimensional stability during fabrication and positioning, and a compliant solder layer that absorbs thermal and mechanical stress. This segmentation allows the structure to maintain its shape while protecting the device from stress-related damage.
Solution Approach 2:
The invention employs a composite structure combining rigid and compliant materials. The rigid base material (such as copper or tungsten) provides dimensional stability, while the compliant solder material (such as tin-based alloys) absorbs stress, preventing damage to the device while maintaining structural integrity.
4Reliability
If larger interconnect area is used, then reliable electrical connections are achieved, but available area on the die is reduced
Solution Approach 1:
The invention utilizes the vertical dimension by creating a recessed solder region within the interconnect structure. This allows the solder to have sufficient connection area for reliable electrical contact without increasing the horizontal footprint on the die surface, thereby maintaining high connection reliability while preserving die area for other components.
Data Source
AI summary
An integrated device includes a die having a contact pad and a solder cap electrically connected to the contact pad by a multi-layer interconnect pillar. The multi-layer interconnect pillar includes a base reinforcement layer, a cap reinforcement layer, and one or more solder layers disposed between the base reinforcement layer and the cap reinforcement layer.