Polycrystalline CVD Diamond on GaN Substrates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The integration of diamond with gallium nitride (GaN) in semiconductor devices is hindered by high thermal boundary resistance due to the use of dielectric interlayers, which also increases fabrication complexity and expense, while direct growth of diamond on GaN is problematic due to substrate degradation.
Innovation Solution
The development of nano-crystalline diamond seeding techniques and controlled early-stage CVD diamond growth allows for the reduction or elimination of dielectric interlayers, achieving ultra-low and uniform thermal barrier resistance without damaging the GaN substrate, using methods like colloidal suspension of nanocrystalline diamond powder and soft-seeding to ensure effective adhesion and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dielectric interlayers are used between diamond and GaN substrate, then adhesion and protection are improved, but thermal boundary resistance increases and fabrication complexity increases
Solution Approach 1:
The patent removes the dielectric interlayer from the structure by implementing direct diamond growth on the GaN substrate. This extraction eliminates the thermal boundary resistance introduced by the interlayer while maintaining adhesion through direct bonding between diamond and GaN surfaces.
Solution Approach 2:
The patent applies preliminary surface treatment to the GaN substrate before diamond growth, including surface cleaning and activation processes. This preliminary action prepares the GaN surface to directly bond with diamond, providing both adhesion and protection without requiring a dielectric interlayer.
2Reliability
If dielectric interlayers are used between diamond and GaN substrate, then adhesion and protection are improved, but fabrication complexity and expense increase
Solution Approach 1:
The patent eliminates the dielectric interlayer and its associated fabrication steps, thereby reducing fabrication complexity and expense while maintaining reliable adhesion through direct diamond-GaN bonding achieved via surface treatment and controlled growth.
Solution Approach 2:
The patent changes the fabrication parameters by removing the dielectric interlayer deposition step and instead optimizing direct diamond growth parameters on the GaN substrate. This parameter change simplifies the fabrication process while achieving the same adhesion and protection functions.
3Device complexity
If direct diamond growth on GaN is performed, then fabrication complexity is reduced and thermal boundary resistance is lowered, but substrate degradation occurs
Solution Approach 1:
The patent applies surface treatment to the GaN substrate before diamond growth, creating a protected and activated surface that prevents degradation during the diamond growth process. This preliminary action enables direct growth without substrate damage.
Solution Approach 2:
The patent implements preliminary protective measures on the GaN substrate surface, such as surface passivation or activation, that counteract the harmful effects of direct diamond growth. This preliminary anti-action prevents substrate degradation while allowing direct growth to proceed.
4Temperature
If diamond heat-spreaders are brought into close proximity to heat source, then thermal management is improved, but fabrication complexity increases due to additional layers and processes
Solution Approach 1:
The patent removes the dielectric interlayer that separates the diamond heat-spreader from the heat source, bringing them into direct contact. This extraction improves thermal management by eliminating the thermal boundary resistance while the direct growth process keeps fabrication complexity manageable.
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 results in optimized thermal and electronic properties for high-power semiconductor devices, reducing thermal boundary resistance and maintaining the electronic integrity of the GaN layer, enabling improved heat management and performance in high-power applications.
Implementation Method 1
CVD diamond substrates for semiconductor industry can be formed as round wafers with standard diameters. Diamond wafers are manufactured by chemical vapor deposition
Implementation Method 2
plasma enhanced diamond CVD where the energy to dissociate the reactants comes from a microwave source
Implementation Method 3
when considering isotropic behaviors diamond is the most thermally conductive substance known to man at room temperature
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A semiconductor device structure comprising: a layer of single crystal compound semiconductor material; and a layer of polycrystalline CVD diamond material, wherein the layer of polycrystalline CVD diamond material is bonded to the layer of single crystal compound semiconductor material via a bonding layer having a thickness of less than 25 nm and a thickness variation of no more than 15 nm, wherein an effective thermal boundary resistance (TBReff) as measured by transient thermoreflectance at an interface between the layer of single crystal compound semiconductor material and the layer of polycrystalline CVD diamond material is less than 25 m2K/GW with a variation of no more than 12 m2K/GW as measured across the semiconductor device structure, and wherein the layer of single crystal compound semiconductor material has one or both of the following characteristics: a charge mobility of at least 1200 cm2V-1s-1; and a sheet resistance of no more than 700 Ω/square.