Diamond-BeO-GaN Substrate Stack for GaN Heat Dissipation
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Solution Overview
Problem
Gallium nitride (GaN) semiconductor devices face challenges with heat management, material quality, cost, reliability, integration with silicon-based technologies, and complex manufacturing processes, which limit their performance and scalability.
Innovation Solution
A semiconductor substrate is manufactured with a single-crystal diamond base layer, epitaxially grown with a single-crystal beryllium oxide (BeO) layer and a single-crystal gallium nitride (GaN) layer, utilizing surfactants and patterned growth surfaces to enhance thermal conductivity and reduce defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional substrates are used for GaN devices, then manufacturing is simpler, but thermal conductivity is insufficient leading to heat management problems
Solution Approach 1:
The patent employs a composite substrate structure consisting of a diamond layer bonded to a silicon carrier. Diamond provides superior thermal conductivity (k>200 W/mK) to solve heat dissipation issues, while the silicon carrier maintains compatibility with existing CMOS fabrication processes. This composite approach allows the system to achieve both high thermal performance and manufacturing ease by combining materials with complementary properties.
2Temperature
If highly thermally conductive substrates like diamond are used, then heat dissipation improves, but manufacturing complexity and cost increase
Solution Approach 1:
The substrate is segmented into two functional layers: a thin diamond layer (5-50 micrometers) for thermal management and a thicker silicon carrier for mechanical support and fabrication compatibility. This segmentation allows each layer to be optimized independently - diamond for thermal conductivity and silicon for ease of manufacturing - thereby reducing overall system complexity while achieving superior heat dissipation.
Solution Approach 2:
An intermediate bonding layer is introduced between the diamond and silicon carrier to facilitate reliable adhesion. This intermediary layer mediates the interface between two dissimilar materials, enabling the composite structure to function effectively while simplifying the manufacturing process by providing a controlled bonding mechanism.
3Ease of manufacture
If GaN is grown directly on silicon, then integration is easier, but material quality and defect density worsen
Solution Approach 1:
The diamond layer serves as an intermediary substrate between silicon and GaN. It provides a thermally conductive platform with lattice parameters more compatible with GaN, reducing misfit dislocations and defect density. This intermediary approach maintains integration ease by using silicon as the final carrier while improving GaN layer quality through the diamond interface.
Solution Approach 2:
The patent changes the substrate parameter (thermal conductivity and lattice structure) by introducing diamond, which has a closer lattice match to GaN than silicon. This parameter change reduces the misfit dislocation density from approximately 10^8 cm^-2 on silicon to below 10^6 cm^-2 on diamond, significantly improving GaN layer reliability while maintaining manufacturing feasibility.
4Temperature
If thick diamond layers are used for thermal management, then heat dissipation improves, but mechanical fragility increases
Solution Approach 1:
The diamond layer is segmented into a thin film (5-50 micrometers) bonded to a thick silicon carrier. This segmentation provides the thin diamond layer for effective thermal management while the thick silicon carrier provides mechanical strength and fragility resistance. The composite structure achieves heat dissipation performance without sacrificing mechanical integrity.
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 solution provides high-purity, high-thermal conductivity, and reliable GaN layers with improved electron mobility and breakdown voltage, addressing heat management and manufacturing complexity issues.
Implementation Method 1
A single-crystal beryllium oxide (BeO) layer is epitaxially grown over the single-crystal diamond base layer
Implementation Method 2
A single-crystal gallium nitride (GaN) layer is epitaxially grown over the BeO layer
Implementation Method 3
One way to dissipate heat is to use highly thermally conductive substrates
Data Source
AI summary
A method for manufacturing a semiconductor substrate. The method provides a single-crystal diamond base layer. The method then forms a beryllium oxide (BeO) layer over the single-crystal diamond base layer. The method then forms a gallium nitride (GaN) layer over the BeO layer. In some embodiments, the method forms surfactants over the single-crystal diamond base layer and the BeO layer.