Hybrid-Bonded Semiconductor Packages With Low-Temperature Solder Pads
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving high integration density and small form factor packaging due to the limitations of existing packaging techniques, particularly in Package-on-Package (PoP) technology, where there is a need for innovative bonding methods to reduce size and enhance functionality.
Innovation Solution
The use of hybrid bonding techniques, specifically face-to-face (F2F) or face-to-back (F2B) configurations, combined with solder bonding instead of copper-to-copper bonding, allows for lower bonding temperatures and more compact package designs by recessing bond pads and utilizing dielectric-to-dielectric and metal bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If copper-to-copper bonding is used in PoP technology, then bonding strength is improved, but bonding temperature increases causing thermal stress and potential damage to insulating layers
Solution Approach 1:
The patent introduces a solder material as an intermediary bonding layer between the first and second bond pads. This solder intermediary enables bonding at lower temperatures (below the reflow temperature of the insulating layers) while still achieving strong mechanical and electrical connections, thus resolving the contradiction between bonding strength and bonding temperature
Solution Approach 2:
The patent changes the bonding parameters by using solder material with a lower melting point than copper. This parameter change allows the bonding process to occur at reduced temperatures that do not damage the insulating layers, while maintaining adequate bonding strength through the solder's metallurgical bonding properties
2Length of moving object
If bond pads are recessed to reduce package height, then package size is reduced, but bonding process complexity increases
Solution Approach 1:
The patent performs preliminary actions by forming the recesses in the bond pads before the bonding process. This allows the solder material to be deposited conformally in the recesses, ensuring proper fill and reducing the need for complex post-bonding adjustments, thus managing process complexity while achieving compact packaging
Solution Approach 2:
The recessed bond pad structure creates a nested configuration where the solder material is contained within the recesses of the bond pads. This nesting approach reduces the overall package height while maintaining bonding integrity, as the solder is properly contained and positioned within the recessed structures
3Stress or pressure
If dielectric-to-dielectric bonding is used, then thermal stress is reduced, but bonding temperature requirements increase
Solution Approach 1:
The solder material serves as a thermal stress-absorbing intermediary between the dielectric layers. While dielectric-to-dielectric bonding reduces thermal stress compared to metal-to-metal bonding, the solder intermediary further mitigates thermal stress through its ductility and thermal expansion properties, while its lower melting point keeps the actual bonding temperature below damage thresholds
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 approach enables the creation of smaller, more integrated semiconductor packages with enhanced bonding strength and reduced thermal stress, while also lowering the reflow temperature to prevent damage to insulating layers.
Implementation Method 1
the conductive bonding material having a reflow temperature lower than reflow temperatures of the first and second bond pads
Implementation Method 2
the second insulating layer being bonded to the first insulating layer through dielectric-to-dielectric bonds
Implementation Method 3
utilizing dielectric-to-dielectric and metal bonding
Data Source
AI summary
In an embodiment, a package includes a first package structure including a first die having a first active side and a first back-side, the first active side including a first bond pad and a first insulating layer a second die bonded to the first die, the second die having a second active side and a second back-side, the second active side including a second bond pad and a second insulating layer, the second active side of the second die facing the first active side of the first die, the second insulating layer being bonded to the first insulating layer through dielectric-to-dielectric bonds, and a conductive bonding material bonded to the first bond pad and the second bond pad, the conductive bonding material having a reflow temperature lower than reflow temperatures of the first and second bond pads.