4D Memory Integration via Fine Pitch Transfer Joining
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Solution Overview
Problem
Current 3D integration technologies face challenges in increasing memory density, cooling efficiency, and electro-static discharge protection, leading to limitations in the number of devices that can be stacked due to heat dissipation and signal delay issues.
Innovation Solution
A 4D system integration technique that increases memory density up to 100× within a single clock cycle, incorporates micro-channel cooling, and supports high I/O density through vertical stacked slices with fine pitch transfer joining connections, enabling efficient power and ground distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If more devices are stacked in 3D integration, then memory density increases, but heat dissipation becomes difficult and signal delay increases
Solution Approach 1:
The patent transitions from traditional 3D stacking to 4D integration by adding temporal dimension through wafer bonding sequences. Multiple wafers are bonded in a time-ordered sequence (first wafer, second wafer, third wafer, etc.), enabling dense integration while maintaining thermal management through staged processing and intermediate cooling opportunities.
2Quantity of substance
If more devices are stacked in 3D integration, then memory density increases, but signal delay increases
Solution Approach 1:
The integration process is segmented into discrete wafer bonding stages. Each wafer is processed and bonded independently in sequence, allowing signal paths to be optimized within each stage while building overall system density. This modular approach reduces cumulative signal delay compared to monolithic stacking.
3Quantity of substance
If through-Si connection is used for wafer-level 3DI, then I/O density increases, but manufacturing complexity increases
Solution Approach 1:
Through-Si vias are formed and prepared in advance on each wafer before bonding. The via structures, including insulation layers and conductive fills, are pre-configured during individual wafer processing. This preliminary preparation simplifies the bonding process and reduces manufacturing complexity compared to forming connections after stacking.
4Temperature
If micro-channel cooling is incorporated, then heat dissipation improves, but device structure becomes more complex
Solution Approach 1:
The wafer structures serve multiple functions: they provide both the computational/memory device functionality and the thermal management pathway through integrated micro-channel cooling. The same wafer substrate that holds the devices also contains the cooling channels, eliminating the need for separate cooling structures and reducing overall system complexity.
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
The 4D system achieves significantly higher memory density and improved cooling capabilities, reducing signal delays and electro-static discharge challenges, allowing for more devices to be stacked while maintaining efficient heat dissipation.
Implementation Method 1
micro-channel cooling
Implementation Method 2
micro-channel cooling
Implementation Method 3
fine pitch transfer joining connections, enabling efficient power and ground distribution
Data Source
AI summary
A 4D device comprises a 2D multi-core logic and a 3D memory stack connected through the memory stack sidewall using a fine pitch T&J connection. The 3D memory in the stack is thinned from the original wafer thickness to no remaining Si. A tongue and groove device at the memory wafer top and bottom surfaces allows an accurate stack alignment. The memory stack also has micro-channels on the backside to allow fluid cooling. The memory stack is further diced at the fixed clock-cycle distance and is flipped on its side and re-assembled on to a template into a pseudo-wafer format. The top side wall of the assembly is polished and built with BEOL to fan-out and use the T&J fine pitch connection to join to the 2D logic wafer. The other side of the memory stack is polished, fanned-out, and bumped with C4 solder. The invention also comprises a process for manufacturing the device. In another aspect, the invention comprises a 4D process and device for over 50× greater than 2D memory density per die and an ultra high density memory.