Nanostructured Thermal Interface for Semiconductor Heat Removal
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Solution Overview
Problem
Current heat transfer technologies face limitations in thermal boundary conductance between high thermal conductivity substrates and semiconductor devices, leading to performance and lifespan issues in microelectronics, particularly for wide-bandgap semiconductors, due to interfacial resistance and thermal stress.
Innovation Solution
The method involves nanostructuring the surfaces of the semiconductor devices and substrates to create high-aspect-ratio features, functionalizing them, and bonding with an intermediate thermal interface material to increase interfacial surface area and phonon impedance matching, enhancing thermal boundary conductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct bonding of semiconductor devices to high thermal conductivity substrates is used, then thermal boundary conductance is limited by interfacial resistance, but device performance and lifespan are degraded due to poor heat removal
Solution Approach 1:
The patent transforms the flat two-dimensional interface into a three-dimensional nanostructured interface with high-aspect-ratio features (pillars, wires, or cones). This dimensional enhancement increases the interfacial surface area by a factor of 5 or more, thereby significantly improving thermal boundary conductance and heat removal efficiency while maintaining device reliability
Solution Approach 2:
The patent modifies the physical and chemical parameters of the interface by nanostructuring the surfaces and applying intermediate thermal interface materials. The nanostructuring changes the geometric parameters (surface area, aspect ratio), while the intermediate materials change the thermal and mechanical properties, achieving both improved heat transfer and stress management
2Loss of energy
If nanostructured surfaces with high aspect ratio features are created, then interfacial surface area increases and thermal boundary conductance improves, but manufacturing complexity increases
Solution Approach 1:
The patent segments the interface into discrete high-aspect-ratio nanostructures (pillars, wires, or cones) arranged in arrays. This segmentation approach allows the complex nanostructuring to be achieved through standardized fabrication processes like self-aligned reactive ion etching, reducing overall manufacturing complexity compared to creating entirely new nanostructure types
Solution Approach 2:
The patent performs preliminary nanostructuring of the surfaces before final bonding. This preliminary action allows the complex nanostructures to be formed while the materials are still accessible for processing, using self-aligned techniques that simplify subsequent bonding steps and reduce overall manufacturing complexity
3Loss of energy
If roughness is increased at the interface, then thermal boundary conductance increases linearly with interfacial area, but stress management during thermal cycling is compromised
Solution Approach 1:
The patent changes the geometric parameters of the interface by creating controlled nanostructures with specific aspect ratios and dimensions. These parameter changes allow simultaneous optimization of thermal boundary conductance (through increased surface area) and stress management (through compliance of the nanostructured intermediate layer during thermal expansion)
Solution Approach 2:
The patent designs the nanostructured intermediate layer to accommodate thermal expansion differences between the semiconductor device and substrate. The high-aspect-ratio features provide mechanical compliance that absorbs thermal stress during cycling while maintaining intimate thermal contact, thus managing both heat transfer and thermal stress
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 significantly increases thermal boundary conductance by up to five times that of flat interfaces, improving heat transfer efficiency and device lifespan while being robust and amenable to manufacturing.
Implementation Method 1
increasing the surface area of the interface by subtractively nanostructuring at least one of the first surface and the substrate to create a nanostructured surface with features having an aspect ratio of at least 1.1:1 or exceeding 10 nm in height
Implementation Method 2
an intermediate layer can improve TBC by serving as a phonon impedance matching layer to bridge two materials with a sharp contrast in vibrational properties
Implementation Method 3
the use of an intermediate thermal interface material (TIM) to bond two surfaces... While the intermediate material necessarily adds some thermal resistance, it fills any voids and can alleviate stress during thermal cycling
Data Source
AI summary
Methods and apparatus for creating an interface between a surface and a substrate, where the thermal conductivity of the substrate exceeds that of the surface. At least one of the surface and the substrate is subtractively nanostructured to create a nanostructured surface, each nanostructured surface is functionalized, and the surface is bonded to the substrate. The nanostructured surface may be functionalized using at least one of the processes of surface acid etching, oxygen plasma etching, atomic layer deposition, sputtering, e-beam deposition, and ion-beam bombardment or implantation, with or without subsequent reflow.