Recess-Filled Metallic Interconnects for Ambient-Temperature Bonding
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Solution Overview
Problem
Challenges arise in forming reliable bonds between stacked semiconductor dies due to uneven bonding surfaces caused by processing techniques like CMP, which can lead to recesses and require high annealing temperatures, limiting packaging schemes and materials.
Innovation Solution
The technique involves forming recesses in interconnect structures and filling them with conductive materials to create a eutectic alloy mass, allowing for direct bonding at ambient temperatures without adhesives, thereby remedying surface topology issues and reducing bonding temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical-mechanical polishing (CMP) is used to prepare bonding surfaces, then surface flatness is improved, but recesses are formed in embedded metallic structures
Solution Approach 1:
The patent applies preliminary action by forming recesses in the embedded metallic structures before the bonding process. These recesses are intentionally created to accommodate the metallic structures from the opposing die, ensuring that the metallic structures make intimate contact during bonding without requiring excessive polishing that would create harmful recesses.
Solution Approach 2:
The patent converts the harmful effect of CMP-induced recesses into a beneficial feature. Instead of viewing recesses as defects to be eliminated, the invention intentionally forms recesses that match the opposing metallic structures, transforming the polishing-induced topology variations into advantageous bonding features that ensure intimate contact.
2Strength
If heated annealing techniques are used to bond metallic structures, then bond strength is improved, but temperature constraints limit packaging schemes and materials
Solution Approach 1:
The patent applies parameter changes by modifying the bonding temperature parameter from high temperatures to ambient temperature. This is achieved through direct bonding techniques that rely on intimate contact between prepared surfaces and metallic structures, eliminating the need for thermal energy to activate bonding while maintaining strong bonds.
Solution Approach 2:
The patent replaces the thermal field (heated annealing) with a mechanical field (direct contact pressure). Instead of using heat to activate bonding, the invention uses mechanical pressure to force the prepared surfaces and metallic structures into intimate contact, allowing bonding to occur at ambient temperature through direct mechanical interaction.
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 enables the formation of reliable low-temperature metallic bonds between semiconductor dies, improving bond strength and conductivity while reducing the need for high-temperature annealing, thus expanding the range of compatible materials and packaging schemes.
Implementation Method 1
bonding the bonding surface of the second substrate to the bonding surface of the first substrate via direct bonding without adhesive
Data Source
AI summary
Devices and techniques including process steps make use of recesses in conductive interconnect structures to form reliable low temperature metallic bonds. A fill layer is deposited into the recesses prior to bonding. First conductive interconnect structures are bonded at ambient temperatures to second metallic interconnect structures using direct bonding techniques, with the fill layers in the recesses in one or both of the first and second interconnect structures.