Hybrid-Fusion DRAM Stack Bonding for High-Capacity Memory
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Solution Overview
Problem
Existing semiconductor memory devices face challenges in achieving high-bandwidth, high-capacity memory stacks with cost-effective process cycles and improved thermal and electrical performance, particularly in applications requiring extensive memory capacity like artificial intelligence.
Innovation Solution
A hybrid-fusion bonding technique combining face-to-face fusion bonding and back-to-back hybrid bonding is employed to create a high-bandwidth, high-capacity memory stack, utilizing oxide-to-oxide bonding for front sides and metal-to-metal bonding for back sides of memory chips, reducing process costs and cycle times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hybrid bonding is used to couple memory chips, then manufacturing precision and bonding strength are improved, but process complexity and cost increase
Solution Approach 1:
The patent segments the bonding process into two distinct types: hybrid bonding for back-to-back chip coupling and fusion bonding for face-to-face chip coupling. This segmentation allows each bonding method to be optimized independently, reducing overall process complexity while maintaining high manufacturing precision where needed.
Solution Approach 2:
The patent applies different bonding methods to different locations of the memory stack: hybrid bonding is used at back interfaces where precise electrical connections are critical, while fusion bonding is used at front interfaces where simpler mechanical coupling suffices. This local differentiation optimizes manufacturing precision at critical points without unnecessarily increasing complexity throughout the entire system.
2Quantity of substance
If more memory chips are stacked to increase capacity, then memory capacity is improved, but thermal management difficulty and process cycle time increase
Solution Approach 1:
The patent performs preliminary actions by pre-processing chip surfaces with specific bonding structures and materials before stacking. This allows faster bonding operations during assembly, reducing the overall process cycle time even as the number of stacked chips increases to boost memory capacity.
Solution Approach 2:
The patent transitions from two-dimensional planar memory layouts to three-dimensional vertical stacking. This dimensional change enables significantly increased memory capacity within the same footprint while the alternating bonding approach manages the thermal and process complexity that arises from the increased stack height.
3Reliability
If hybrid bonding is used for back-to-back coupling, then electrical performance is improved, but manufacturing cost increases
Solution Approach 1:
The patent segments the bonding applications by electrical performance requirements: hybrid bonding is applied only where electrical connections are critical (back-to-back interfaces), while fusion bonding is used where electrical performance requirements are lower (face-to-face interfaces). This segmentation maintains necessary electrical performance while reducing overall manufacturing cost.
Solution Approach 2:
The patent changes the bonding parameter (method type) based on the specific interface requirements. By adjusting which bonding method is used at each interface, the system achieves optimal electrical performance at critical interfaces while minimizing manufacturing costs at less critical interfaces.
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 provides a cost-effective solution for high-bandwidth, high-capacity DRAM stacks with improved thermal and electrical performance, suitable for memory-intensive applications such as artificial intelligence, while maintaining a compact form factor.
Implementation Method 1
a front side of the first memory chip is coupled to a front side of the second memory chip
Implementation Method 2
a back side of the second memory chip is coupled to a back side of the third memory chip through hybrid bonding
Data Source
AI summary
A device comprising a memory device comprising: a first memory chip; a second memory chip coupled to the first memory chip, wherein a front side of the first memory chip is coupled to a front side of the second memory chip; a third memory chip coupled to the second memory chip, wherein a back side of the second memory chip is coupled to a back side of the third memory chip through hybrid bonding; and a fourth memory chip coupled to the third memory chip, wherein a front side of the third memory chip is coupled to a front side of the fourth memory chip.