Epitaxial Semiconductor Layer on Diamond Heat Spreader
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Solution Overview
Problem
Conventional methods face challenges in achieving low surface roughness for single-crystal and polycrystalline diamond heat spreaders, leading to voids and inefficient heat transfer when bonding with high power devices, and existing solutions like capillary fluid and indium alloy solder fail to effectively wet the rough surfaces of polycrystalline diamonds.
Innovation Solution
A semiconductor layer is epitaxially grown on a diamond substrate with a surface root mean square (RMS) roughness of about 5 nm or less, using techniques like low-temperature molecular beam epitaxy (LT-MBE) and surface treatment methods such as polishing, to facilitate direct bonding with a heat source without voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If single-crystal diamond is used as heat spreader, then thermal conductivity is improved, but surface roughness control becomes difficult and cost increases
Solution Approach 1:
A semiconductor layer is introduced as an intermediary between the diamond substrate and the heat source. This intermediate layer acts as a mediator that can be precisely controlled during epitaxial growth to achieve smooth surfaces (RMS roughness of 0.5 nm or less), while the diamond substrate maintains its superior thermal conductivity properties. The semiconductor layer compensates for the difficulty in controlling surface roughness of single-crystal diamond.
2Ease of manufacture
If polycrystalline diamond is used as heat spreader, then cost is reduced, but surface roughness increases and voids are generated at interface
Solution Approach 1:
The semiconductor layer serves as an intermediary that covers the rough surface of polycrystalline diamond. During epitaxial growth, this layer forms a smooth interface (RMS roughness of 0.5 nm or less) that eliminates voids between the heat spreader and heat source, while allowing the use of cost-effective polycrystalline diamond substrate.
Solution Approach 2:
The surface roughness parameter is transformed from the diamond substrate level to the semiconductor layer level. By controlling epitaxial growth parameters, the semiconductor layer achieves a smooth surface (RMS ≤ 0.5 nm) even when grown on rough polycrystalline diamond, effectively decoupling the cost advantage of polycrystalline diamond from its surface roughness disadvantage.
3Ease of manufacture
If conventional bonding methods (capillary fluid or indium solder) are used, then bonding is achieved, but wetting of rough surface is insufficient and voids remain
Solution Approach 1:
The semiconductor layer replaces conventional bonding materials (capillary fluid or indium solder) as the intermediary between diamond and heat source. This epitaxial layer provides superior wetting and bonding characteristics, achieving complete interface coverage without voids and achieving RMS roughness of 0.5 nm or less, which conventional bonding methods cannot achieve on rough surfaces.
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 approach enables efficient heat spreading by eliminating voids at the interface, improving thermal conductivity, and reducing thermal resistance, while being cost-effective compared to traditional indium solders.
Implementation Method 1
a semiconductor layer can be epitaxially formed on a diamond substrate
Implementation Method 2
single-crystal diamond is an effective heat spreader due to its high thermal conductivity
Data Source
AI summary
Various embodiments provide methods for forming a diamond heat spreader and integrating the diamond heat spreader with a heat source without generating voids at the interface. In one embodiment, a semiconductor layer can be epitaxially formed on a diamond substrate having a desirably low surface root mean square (RMS) roughness. The semiconductor epi-layer can be used as an interface layer for bonding the diamond substrate to the heat source to provide efficient heat spreading.