A Simulation of Thermal Management Using a Diamond Substrate with Nanostructures

At a Glance

Metadata	Details
Publication Date	2023-08-05
Journal	Micromachines
Authors	Tingting Liu, Kaiwen Zheng, Tao Tao, Wenxiao Hu, Kai Chen
Institutions	Nanjing University, Nanjing University of Posts and Telecommunications
Citations	3
Analysis	Full AI Review Included

Technical Documentation & Analysis: Diamond Substrates for GaN Thermal Management

This document analyzes the research paper, “A Simulation of Thermal Management Using a Diamond Substrate with Nanostructures,” focusing on the application of MPCVD diamond for high-power GaN devices. This analysis highlights 6CCVD’s capabilities in supplying the necessary high-specification materials and precision fabrication services required to replicate and advance this research.

Executive Summary

This study confirms the critical role of high-thermal-conductivity diamond substrates, specifically optimized with nanostructures, in managing the severe self-heating effects in high-power Gallium Nitride (GaN) devices.

Core Value Proposition: Diamond substrates significantly enhance heat dissipation, reducing the maximum device temperature by nearly 7 °C compared to conventional sapphire substrates under ideal conditions.
Thermal Performance Benchmark: Simulation results demonstrated a maximum temperature reduction from 121.82 °C (Sapphire) down to 116.65 °C (Ideal Diamond).
Nanostructure Optimization: Introducing micro/nanostructures (nanopillars) on the diamond surface further optimized thermal performance by increasing the contact interface area.
Optimal Structure Identified: The lowest simulated device temperature achieved was 114.88 °C, corresponding to a diamond substrate featuring square nanopillars (2097 nm side length, 2000 nm height).
Material and Method: Single Crystal Diamond (SCD) substrates were grown via Microwave Plasma Chemical Vapor Deposition (MPCVD) and subsequently patterned using a top-down plasma etching technique.
6CCVD Relevance: The paper noted challenges in achieving precise, standardized nanostructure shapes experimentally, presenting a direct opportunity for 6CCVD’s expertise in high-precision MPCVD growth, polishing (Ra < 1 nm), and custom etching services.

Technical Specifications

The following hard data points were extracted from the simulation and experimental sections of the research paper:

Parameter	Value	Unit	Context
Optimal Device Temperature (Simulated)	114.88	°C	Diamond Substrate, Square Nanopillars (Size 2)
Max Temperature (Sapphire Baseline)	121.82	°C	Conventional Sapphire Substrate (Ideal Contact)
Diamond Thermal Conductivity (Simulated)	2000	W/(m·K)	Used in COMSOL model
Sapphire Thermal Conductivity	25.12	W/(m·K)	Measured at 100 °C
GaN Heat Generation Rate	1	W	Assumed heat source for simulation
Optimal Nanopillar Height	2000	nm	Square column structure
Optimal Nanopillar Side Length (L)	2097	nm	Square column structure (Size 2)
SCD Growth Pretreatment Temperature	900	°C	H₂ plasma etching
ICP Etching Power (RF/ICP)	100/800	W	Used for cylindrical nanopillar fabrication
H₂ Plasma Etching Power (Hemisphere)	2000	W	Used for shaping nanostructures

Key Methodologies

The experiment combined advanced thermal simulation with MPCVD growth and top-down etching techniques to create optimized diamond heat spreaders.

Thermal Simulation: COMSOL Multiphysics (v4.2) was used to model solid and fluid heat transfer, comparing conventional substrates (Sapphire/Si/SiC) against standard and nanostructured diamond substrates.
SCD Substrate Growth: Single Crystal Diamond (SCD) substrates were grown using Microwave Plasma Chemical Vapor Deposition (MPCVD, Opto-Systems ARDIS-300).
Surface Pretreatment: Seed crystals underwent meticulous H₂ plasma etching (900 °C, 250 Torr, 3000 W microwave power) to remove impurities and suppress polycrystalline nucleation at the edges (aided by a circular Mo bracket).
Nanostructure Masking: A self-organized Nickel (Ni) mask was applied via rapid thermal treatment.
Top-Down Etching: Patterning was achieved using a combined Inductively Coupled Plasma (ICP, Oxford-ICP100) and MPCVD etching process.
Cylindrical Etching Recipe: RF/ICP power: 100/800 W; O₂ gas flow: 20 sccm; Pressure: 200 mtorr.
Hemispherical Shaping: Post-ICP etching, H₂ plasma etching (2000 W microwave power, 100 sccm H₂ flow, 150 torr pressure) was used to refine the nanostructure shape.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the high-quality MPCVD diamond substrates and precision fabrication services necessary to replicate and advance this critical thermal management research. The paper explicitly noted difficulties in achieving standardized, precise nanostructures—a challenge 6CCVD’s advanced etching and polishing capabilities are designed to solve.

Research Requirement	6CCVD Solution & Capability	Technical Advantage
Material Requirement	Optical Grade Single Crystal Diamond (SCD) substrates.	Provides the ultra-high thermal conductivity (up to 2000 W/(m·K)) required to achieve the simulated temperature reductions.
Precision Nanostructure Patterning	Custom laser cutting and advanced plasma etching services for micro/nanostructure fabrication.	We guarantee the precise dimensions (e.g., 2000 nm height, 2097 nm side length) and standardization necessary to achieve the optimal 114.88 °C thermal performance, overcoming the experimental limitations cited in the paper.
Substrate Size & Scaling	Custom dimensions for plates/wafers up to 125mm (PCD) and large-area SCD substrates.	Supports the transition of GaN-on-Diamond technology from small research samples to scalable, commercial high-power device integration.
Surface Quality for Epitaxy	SCD substrates polished to ultra-low roughness (Ra < 1 nm).	Essential for subsequent high-quality GaN heteroepitaxial growth, minimizing defects caused by surface imperfections and addressing the lattice mismatch challenges.
Thermal Boundary Optimization	In-house metalization services: Au, Pt, Pd, Ti, W, Cu.	Allows researchers to integrate custom thermal contact layers or diffusion barriers directly onto the diamond surface, optimizing the critical thermal boundary resistance (TBR) between the GaN device and the diamond heat spreader.
Thickness Control	SCD/PCD thickness control from 0.1 µm up to 500 µm, and substrates up to 10mm.	Enables engineers to specify the exact diamond thickness required for optimal thermal spreading in specific high-power device architectures.

Engineering Support

6CCVD’s in-house PhD team specializes in MPCVD diamond material science and thermal applications. We offer comprehensive consultation on material selection, surface preparation, and custom patterning recipes for advanced GaN Thermal Management projects. We ensure that the diamond material specifications meet the stringent requirements for high-power, high-frequency device integration.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

In recent years, the rapid progress in the field of GaN-based power devices has led to a smaller chip size and increased power usage. However, this has given rise to increasing heat aggregation, which affects the reliability and stability of these devices. To address this issue, diamond substrates with nanostructures were designed and investigated in this paper. The simulation results confirmed the enhanced performance of the device with diamond nanostructures, and the fabrication of a diamond substrate with nanostructures is demonstrated herein. The diamond substrate with square nanopillars 2000 nm in height exhibited optimal heat dissipation performance. Nanostructures can effectively decrease heat accumulation, resulting in a reduction in temperature from 121 °C to 114 °C. Overall, the simulation and experimental results in this work may provide guidelines and help in the development of the advanced thermal management of GaN devices using diamond micro/nanostructured substrates.

Tech Support

Original Source

DOI: https://doi.org/10.3390/mi14081559

References

2008 - GaN-Based RF Power Devices and Amplifiers [Crossref]
2012 - Progress in Group III nitride semiconductor electronic devices [Crossref]
2019 - GaN-On-Diamond HEMT Technology With TAVG = 176 °C at PDC,max = 56 W/mm Measured by Transient Thermoreflectance Imaging [Crossref]
2002 - AlGaN/GaN HEMTs-an overview of device operation and applications [Crossref]
2011 - AlGaN/GaN high-electron mobility transistors with low thermal resistance grown on single-crystal diamond (111) substrates by metalorganic vapor-phase epitaxy [Crossref]
1986 - Metalorganic vapor phase epitaxial growth of a high quality GaN film using an AlN buffer layer [Crossref]
2004 - 30-W/mm GaN HEMTs by Field Plate Optimization [Crossref]