Heat sink efficiency investigation of silicon-on-diamond composite substrates for gallium nitride-based devices
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2022-01-01 |
| Journal | Письма в журнал технической физики |
| Authors | И. С. Езубченко, И. А. Черных, И. А. Черных, А. А. Андреев, I. O. Mayboroda |
| Institutions | Kurchatov Institute |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This documentation analyzes the successful integration of MPCVD diamond composite substrates for high-power Gallium Nitride (GaN) devices, demonstrating a critical advancement in thermal management and device reliability.
- Thermal Performance: GaN-on-Diamond (GaN-on-D) composite substrates achieved a surface temperature reduction of over 50°C compared to standard GaN-on-SiC at dissipation powers exceeding 7 W.
- Reliability Enhancement: The reduction in channel temperature (maintaining it below 200°C) translates directly to an increase in Mean Time Before Failure (MTBF) by a factor of 100 or more.
- Power Density Increase: The suppression of self-heating allowed for a 37% increase in maximum dissipated power (up to 13 W) compared to commercial GaN-on-SiC devices (6.25 W limit).
- Material Validation: The study validates the use of high-quality Polycrystalline Diamond (PCD) films, grown via Microwave Plasma-Enhanced Chemical Vapor Deposition (MPCVD), with thermal conductivity ranging from 800-1800 W/(m·K).
- Scalability: The approach was demonstrated on 15 x 15 mm substrates, confirming the potential for scalable manufacturing of high-power microwave devices.
- Operational Stability: GaN-on-D structures showed no self-heating effects in Current-Voltage Curve (CVC) measurements up to the maximum tested supply voltage of 15 V.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the thermometric measurements comparing GaN-on-SiC and GaN-on-Diamond structures.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Thermal Conductivity (PCD) | 800-1800 | W/(m·K) | Range cited for MPCVD polycrystalline diamond films |
| Maximum Dissipated Power (GaN-on-D) | >13 | W | Power level achieved before channel temperature reached 200°C (ΔT = 115°C) |
| Maximum Dissipated Power (GaN-on-SiC) | 6.25 | W | Manufacturer recommended limit (184°C surface temperature) |
| Temperature Increment Reduction (at 8.5 W) | >50 | °C | Difference between GaN-on-SiC (ΔT > 120°C) and GaN-on-D (ΔT < 70°C) |
| MTBF Improvement Factor | 100+ | N/A | Achieved by maintaining channel temperature below 200°C |
| Max Drain Current Density (GaN-on-D) | 0.88 | A/mm | Interdigitated structures, measured up to 15 V |
| Base Operating Temperature | 85 | °C | Reference temperature for device operation |
| Gold Metalization Thickness (Base) | 5 | µm | Electrodeposited layer on Cu-W pseudoalloy package base |
| Thermal Measurement Resolution | 0.75 | µm/pixel | Achieved using QFI InfraScope temperature mapping microscope |
Key Methodologies
Section titled “Key Methodologies”The experiment focused on integrating and characterizing GaN heterostructures on composite silicon-on-diamond substrates.
- Substrate Fabrication: Device-quality GaN heterostructures were produced on 15 x 15 mm silicon-on-diamond composite substrates.
- Diamond Growth: Polycrystalline diamond films were grown using Microwave Plasma-Enhanced Chemical Vapor Deposition (MPCVD).
- Packaging: Transistor crystals were mounted into a ceramic-and-metal power transistor package.
- Soldering: A 25 µm thick foil of eutectic Au80/Sn20 alloy was used for soldering to minimize crystal-package thermal resistance.
- Package Base: The base was a 2.5 mm thick Cu-W pseudoalloy plate, coated with an electrodeposited gold layer (5 µm thickness).
- Bonding: Internal leads were bonded using 25.4 µm diameter gold wire.
- Thermal Measurement Setup: Surface temperature dependence on dissipated power was measured in DC mode using a QFI InfraScope temperature mapping microscope.
- Instrumentation: Measurements utilized a MWIR camera (1-5 µm wavelength) cooled by liquid nitrogen, achieving a temperature sensitivity of 0.1°C.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”This research confirms that high-quality MPCVD diamond is essential for achieving next-generation performance in GaN-based RF and power electronics. 6CCVD is uniquely positioned to supply the required materials and custom engineering services necessary to replicate and advance this technology.
| Research Requirement/Challenge | 6CCVD Solution & Capability | Technical Advantage |
|---|---|---|
| Material: High Thermal Conductivity PCD (800-1800 W/(m·K)) | Polycrystalline Diamond (PCD) Wafers. We specialize in high-purity MPCVD PCD engineered for superior thermal management applications. | Guarantees the necessary thermal performance to suppress self-heating and achieve the demonstrated 100x MTBF increase. |
| Dimensions: 15 x 15 mm Substrates | Custom Dimensions up to 125 mm. We supply large-area PCD plates and wafers, enabling scalable production far beyond the small dimensions used in this study. | Supports high-volume manufacturing (HVM) and larger device footprints for high-power microwave systems. |
| Thickness Control: Precise diamond layer thickness (0.1 µm to 500 µm range) | SCD and PCD Thickness Control. We offer precise thickness control for both Single Crystal (SCD) and Polycrystalline (PCD) films from 0.1 µm up to 500 µm. | Allows engineers to optimize the diamond layer thickness to minimize Thermal Boundary Resistance (TBR) while maximizing heat spreading. |
| Surface Quality: Low interfacial thermal resistance | Advanced Polishing Services. We provide ultra-smooth polishing for inch-size PCD wafers (Ra < 5 nm) and SCD wafers (Ra < 1 nm). | Ensures optimal bonding and low thermal resistance at the GaN/Diamond interface, critical for efficient heat transfer. |
| Metalization: Gold (Au) layer for bonding (e.g., Au/Sn eutectic) | In-House Custom Metalization. 6CCVD offers internal deposition capabilities for Au, Pt, Pd, Ti, W, and Cu. | Provides turnkey, integrated solutions for device packaging, matching the specific Au metalization requirements used for low-resistance soldering in this research. |
| Logistics: Global supply chain | Global Shipping (DDU/DDP). We ship worldwide, handling complex logistics to ensure timely delivery of critical materials. | Simplifies procurement for international research teams and manufacturers. |
Engineering Support
Section titled “Engineering Support”6CCVD’s in-house PhD team possesses deep expertise in MPCVD diamond growth and thermal modeling. We can assist engineers and scientists with material selection, interface optimization, and custom specifications for similar GaN-on-Diamond RF Power Amplifier projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
In this work, thermometric measurements of gallium nitride-based ungated transistors on silicon-on-diamond composite substrates are performed. Their heat sink efficiency is compared with transistors made by standard technology on a silicon carbide substrates. Reducing of the surface temperature by more than 50 o C using new type of silicon-on-diamond composite substrates at dissipation power above 7 W is shown. The proposed approach is promising for increasing the output power and reliability of gallium nitride-based devices. Keywords: gallium nitride, heat sink, diamond, dissipation power.