Multi-Level Wick Structures for Vapor Chamber Heat Dissipation
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Solution Overview
Problem
Conventional cleanroom techniques are unable to fabricate fully 3D hierarchical wick structures for effective heat dissipation in high-power electronic devices, as they struggle with achieving uniform photoresist coating and etching multi-depth features, leading to unsatisfactory thermal performance and fluid rerouting limitations.
Innovation Solution
An unconventional process flow using a Silicon Oxide etch mask layer allows for multiple rounds of lithography and deep silicon etching, enabling the creation of monolithically fabricated multi-level 3D wick structures with precise control over step heights, overcoming the limitations of conventional methods by using Chemical Vapor Deposition (CVD) and High Density Plasma Enhanced CVD (HDPECVD) to deposit Silicon Oxide, which acts as a hard mask for deep silicon etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional cleanroom techniques are used to fabricate wick structures, then manufacturing process simplicity is maintained, but manufacturing precision and structural complexity are limited
Solution Approach 1:
The fabrication process is segmented into multiple discrete lithography and etching steps, each creating a specific level of the hierarchical wick structure. This allows complex 3D structures to be built systematically through repeated application of standard cleanroom techniques, resolving the contradiction between manufacturing precision and process complexity.
Solution Approach 2:
The patent transitions from conventional 2D wick structures to multi-level 3D hierarchical structures by adding the vertical dimension through controlled etching at different depths. This dimensional expansion enables complex fluid routing paths while maintaining compatibility with standard planar lithography processes.
2Manufacturing precision
If uniform photoresist coating is applied, then manufacturing simplicity is maintained, but manufacturing precision for multi-depth features deteriorates
Solution Approach 1:
The patent applies preliminary actions by performing multiple lithography patterning steps on the same photoresist layer before the final etch. This allows different regions to be pre-defined with different etch depths, enabling multi-level structures while using uniform photoresist coating techniques throughout the process.
Solution Approach 2:
The photoresist layer acts as an intermediary that stores multiple levels of patterning information through sequential exposure and development. This intermediary layer enables the transfer of complex multi-depth patterns to the underlying substrate without requiring complex coating processes.
3Loss of energy
If single-level wick structures are used, then device simplicity is maintained, but heat dissipation performance deteriorates
Solution Approach 1:
The hierarchical wick structure implements local quality by creating regions with different pore sizes and depths optimized for specific functions: larger pores for bulk fluid transport and smaller pores for capillary action near heat sources. This local optimization significantly improves heat dissipation efficiency while managing structural complexity.
Solution Approach 2:
The patent creates nested hierarchical structures where smaller pore features are embedded within larger pore structures, forming a multi-scale wick network. This nesting arrangement enables simultaneous optimization of fluid transport at multiple scales, dramatically enhancing heat dissipation performance.
4Quantity of substance
If taller pin fins are used for fluid rerouting, then fluid transport capability is improved, but thermal performance at hotspots deteriorates
Solution Approach 1:
The hierarchical wick structure implements local quality by creating regions with different pore sizes and depths optimized for specific functions: larger pores for bulk fluid transport and smaller pores for capillary action near heat sources. This local optimization significantly improves heat dissipation efficiency while managing structural 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
This approach enables the fabrication of hierarchical wick structures with high aspect ratios and multi-level pin arrays, enhancing capillary performance and reducing thermal resistance, allowing for improved heat dissipation and scalability in electronic devices.
Implementation Method 1
using Chemical Vapor Deposition (CVD) and High Density Plasma Enhanced CVD (HDPECVD) to deposit Silicon Oxide
Implementation Method 2
using Chemical Vapor Deposition (CVD) and High Density Plasma Enhanced CVD (HDPECVD) to deposit Silicon Oxide
Implementation Method 3
enhancing capillary performance
Data Source
AI summary
Improved vapor chambers are provided using monolithic wick structures having deep features (≥150 um) and two or more different feature heights above the substrate. Such monolithic multi-level wick structures provide improved performance in vapor chambers by alleviating the tradeoff between fluid transport (which favors tall pin-fins) and heat transfer (which favors short pin-fins).