Electromigration Interconnects for Integrated Circuit Assembly
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Solution Overview
Problem
Current methods for assembling integrated circuits, such as through silicon vias and direct bond interconnects, are costly and time-consuming, and existing capacitive connections have limitations in dimension reduction and application scope.
Innovation Solution
A process involving the formation of cavities in covering regions over metallic lines, direct bonding of these regions, and electromigration to form a metallic assembly, with optional annealing and resistance monitoring to control the assembly process, allowing metal atoms to migrate and fill cavities without damaging the lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through silicon vias (TSVs) are used to connect integrated circuits, then electrical connection between substrates is achieved, but fabrication time and cost increase
Solution Approach 1:
The invention extracts the metallic interconnect function from the substrate itself. Instead of creating TSVs that pass through the entire substrate thickness, the patent uses metallic lines that remain on the substrate surface and form connections through electromigration after bonding, thereby eliminating the time-consuming substrate thinning and deep etching processes
Solution Approach 2:
The invention performs preliminary bonding of the insulating regions before forming the metallic connections. The substrates are bonded together first through their insulating oxide layers, and only then are the metallic lines connected via electromigration, reversing the conventional sequence to simplify the overall fabrication process
2Reliability
If through silicon vias (TSVs) are used to connect integrated circuits, then electrical connection between substrates is achieved, but production cost increases
Solution Approach 1:
The invention extracts the metallic interconnect function from the substrate itself. Instead of creating TSVs that pass through the entire substrate thickness, the patent uses metallic lines that remain on the substrate surface and form connections through electromigration after bonding, thereby eliminating the time-consuming substrate thinning and deep etching processes
Solution Approach 2:
The invention uses the metallic lines' own material to form the interconnect bridge. The electromigration process transfers metal atoms from one metallic line to another, using the material already present in the structure rather than requiring additional deposition or filling materials, thereby reducing production costs
3Loss of time
If oxide bonding is performed without metallic interconnects passing through substrate, then fabrication time and cost are reduced, but metallic connection between lines must be formed differently
Solution Approach 1:
The invention replaces the mechanical/physical process of creating through-substrate vias with an electromagnetic process. Electromigration uses electrical current to drive metal atom diffusion, transforming the connection formation from a mechanical drilling/filling operation to an electromagnetic field-driven material transport process
Solution Approach 2:
The invention changes the physical state and position of the metallic connections. Instead of maintaining metallic lines as static conductors on separate substrates, the electromigration process dynamically changes the metal distribution, creating new conductive pathways that bridge the bonded substrates through controlled material migration
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 method accelerates the formation of a metallic assembly between integrated circuits, reducing fabrication time and costs while enabling precise control over the assembly process, and does not require metallic interconnects passing through substrates.
Implementation Method 1
forming a metallic assembly of the two lines, comprising an electromigration of the metal of at least one of the metallic lines through the cavities
Implementation Method 2
the formation of the metallic assembly furthermore comprises an anneal carried out during the electromigration
Data Source
AI summary
A three-dimensional integrated structure is fabricated by assembling at least two parts together, wherein each part contains at least one metallic line covered with a covering region and having a free side. A cavity is formed in the covering region of each part, that cavity opening onto the metallic line. The two parts are joined together with the free sides facing each other and the cavities in each covering region aligned with each other. The metallic lines are then electrically joined to each other through an electromigration of the metal within at least one of the metallic lines, the electromigrated material filling the aligned cavities.