Air Channel Interconnects for 3D Chip Stack Thermal Management
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Solution Overview
Problem
Current methods for three-dimensional (3D) integrated circuit fabrication face challenges in efficient heat removal, as existing cooling technologies are inadequate for high power density chips, and conventional air dielectric methods suffer from structural weaknesses and fabrication difficulties, leading to ineffective thermal dissipation and signal integrity issues.
Innovation Solution
The implementation of an air channel interconnect network within the 3D chip stack structure, comprising vertically and horizontally interconnected air channels formed between bonded wafers, allowing for air flow through openings to enhance heat removal, which includes processing wafers to form semiconductor devices, circuitry, air vias, and through-silicon vias, and bonding them to create an embedded air channel interconnect network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional air cooling technology is used for heat removal, then the cooling system is simple and easy to implement, but it cannot effectively remove heat from high power density chips (200 W/cm2)
Solution Approach 1:
The patent applies pneumatic cooling by introducing air channels through the wafer structure to enable forced convection of air through the device. This allows efficient heat removal from high power density chips by using pressurized air flow through integrated channels, transforming the cooling approach from external to internal pneumatic cooling.
Solution Approach 2:
The patent transitions from two-dimensional surface cooling to three-dimensional internal cooling by etching channels through the wafer thickness. This vertical dimension allows heat to be conducted to cooling channels located at different depths, enabling effective heat removal from high power density regions that cannot be cooled by surface-level air cooling alone.
2Temperature
If air channels are formed in the wafer for cooling, then heat removal efficiency is improved, but the structural strength and reliability of the wafer are reduced
Solution Approach 1:
The patent applies local quality by selectively removing material only in specific regions where cooling channels are needed, while leaving the rest of the wafer structure intact and strong. The channels are strategically positioned to provide cooling where heat generation occurs, without compromising the overall structural integrity of the wafer.
Solution Approach 2:
The patent uses composite structures by combining the wafer material with bonding adhesive layers that fill and seal the channel openings. This creates a composite structure where the adhesive provides both sealing for the air channels and structural reinforcement to compensate for the material removed during channel formation.
3Adaptability or versatility
If wafer bonding is performed to stack multiple wafers, then three-dimensional integration is achieved, but stringent requirements for wafer cleanliness and flatness make the process difficult
Solution Approach 1:
The patent uses bonding adhesive as an intermediary material between wafers during stacking. This adhesive layer compensates for minor variations in wafer flatness and cleanliness, making the bonding process more tolerant and easier to perform while still achieving reliable mechanical and thermal coupling between stacked wafers.
4Reliability
If vertical interconnections are formed through wafers, then electrical connections between stacked wafers are established, but reliable low-resistance connections are difficult to achieve
Solution Approach 1:
The patent merges multiple functions into the via structures by combining electrical interconnection, mechanical support, and thermal management functions. The same via holes that provide electrical pathways also serve as conduits for air flow in the cooling channels, reducing the total number of structures needed and simplifying the fabrication process while maintaining reliable electrical connections.
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 efficiently removes heat from 3D chip stacks through convection, outperforming conventional copper metallization cooling methods, especially at smaller channel diameters, and improves signal integrity by reducing noise coupling, enabling more compact chip designs and effective thermal management.
Implementation Method 1
air can flow into and out of the air interconnect network through one or more opening to remove heat from the chip stack structure
Data Source
AI summary
A three-dimensional (3D) chip stack structure and method of fabricating the structure thereof are provided. The 3D chip stack structure includes a plurality of vertically stacked chips which are interconnected and bonded together, wherein each of the vertically stacked chips include one or more IC device strata. The 3D chip stack structure further includes an air channel interconnect network embedded within the chip stack structure, and wherein the air channel interconnect network is formed in between at least two wafers bonded to each other of the vertically stacked wafers and in between at least two bonded wafers of the vertically stacked wafers at a bonding interface thereof. In addition, the 3D chip stack structure further includes one or more openings in a peripheral region of the chip stack structure that lead into and out of the air channel interconnect network, so that air can flow into and out of the air channel interconnect network through the one or more openings to remove heat from the chip stack structure.