I. Preface: Interfacial Thermal Resistance, the Invisible Bottleneck for Power Device Heat Dissipation

During the R&D and thermal design of power devices, most enterprises only focus on the thermal conductivity of bulk substrate materials, while long‑term overlooking two core indicators: the thermal conductivity of epitaxial thin films and heterointerfacial thermal boundary conductance (TBC).
Modern semiconductor devices adopt multi‑layer heterostacked structures. Heat must sequentially pass through multiple interfaces including substrates, buffer layers, epitaxial layers and electrodes. Numerous engineering cases have verified that the accumulation of thermal resistance across multi‑layer interfaces, rather than the thermal conduction limitation of the substrate itself, constitutes the core invisible bottleneck restricting heat dissipation of high‑power chips, triggering local overheating and device failure.
Based on cutting‑edge research published in Nature Communications, this paper analyzes the in‑plane and cross‑plane thermal conduction properties of 3C‑SiC epitaxial thin films, as well as thermal boundary conduction characteristics of 3C‑SiC/Si and 3C‑SiC/AlN heterointerfaces. From the perspectives of thin films and interfaces, it disaggregates optimization strategies for power‑device heat dissipation, and provides authoritative measured data for thermal simulation, scheme design and process iteration of wide‑bandgap heterogeneously integrated devices.

II. High‑Quality 3C‑SiC Epitaxial Thin Films: Top‑Tier Thermal Conductivity at Ultra‑Thin Thickness

Due to size effects, phonons in semiconductor thin‑film materials are prone to scattering at upper and lower boundaries. Consequently, thin‑film thermal conductivity is generally far lower than that of bulk counterparts, which greatly increases heat‑dissipation difficulty for ultra‑thin devices. The high‑purity, low‑defect 3C‑SiC thin films prepared in this research break through thermal‑conduction limitations of conventional thin films.
In this experiment, the Beam‑Offset Time‑Domain Thermoreflectance (BO‑TDTR) technique was adopted to measure in‑plane thermal conductivity, while conventional TDTR was used for cross‑plane thermal conductivity measurement for dual verification of thin‑film heat‑dissipation capability. In‑plane thermal conductivity determines lateral hot‑spot spreading capacity of chips, whereas cross‑plane thermal conductivity governs vertical heat extraction toward substrates.
 

[Figure 1] Working principle of BO‑TDTR; comparison of in‑plane and cross‑plane thermal conductivity of 3C‑SiC thin films; temperature‑dependent thermal‑conductivity curves
 
Multiple groups of temperature‑ and thickness‑controlled tests demonstrate that 3C‑SiC thin films deliver industry‑leading thermal‑conduction advantages:

• Superior in‑plane thermal conductivity over diamond thin films: At identical thickness, 3C‑SiC epitaxial thin films exhibit higher in‑plane thermal conductivity than diamond thin films, enabling rapid spreading of local hot spots on chips and eliminating local heat accumulation.

• Cross‑plane thermal conductivity greatly outperforms GaN and AlN: The 1.75 μm‑thick 3C‑SiC thin film achieves 80 % of the thermal conductivity of bulk 3C‑SiC, twice the thermal conductivity of bulk GaN. Even at an ultra‑thin thickness of 0.93 μm, its thermal performance is comparable to bulk GaN.

• Stable performance across full temperature range: Across the entire tested temperature range, both in‑plane and cross‑plane thermal conductivity of 3C‑SiC thin films surpass those of AlN and GaN epitaxial thin films of equivalent specifications.

From an engineering perspective, the active layers of mainstream GaN and SiC power devices are micron‑scale thin‑film structures. Adopting 3C‑SiC as buffer layers or thermal‑spreading layers addresses heat‑dissipation challenges of ultra‑thin chips under device miniaturization and high‑density integration, and meets R&D requirements for high‑end high‑frequency power devices.

III. 3C‑SiC Heteroepitaxial Interfaces: Ultra‑High Thermal Boundary Conductance Resolving Heat‑Dissipation Challenges for Heterogeneous Integration

Heterogeneous integration represents a core industrial trend for wide‑bandgap semiconductors. Composite integration of GaN, SiC with silicon, AlN and other materials balances high performance and low cost. Nevertheless, interfacial thermal resistance induced by dissimilar‑material bonding severely impedes heat transfer and becomes the major bottleneck for performance upgrading of heterogeneous devices.
This research conducts TEM interfacial characterization and precise thermal‑boundary‑conductance measurements on two industrially prevalent structures: 3C‑SiC/Si and 3C‑SiC/AlN.
 

[Figure 2] TEM micrographs of 3C‑SiC/Si and 3C‑SiC/AlN interfaces; bar chart comparing thermal boundary conductance (TBC) among various semiconductor interfaces
 
Interface characterization reveals atomically flat as‑grown epitaxial interfaces without thick amorphous transition layers. Dense interfacial bonding and minimal defects lay a structural foundation for efficient heat conduction. Key measured data are industry‑leading:

• 3C‑SiC/Si interface TBC ≈ 620 MW·m⁻²·K⁻¹: Ranking among the top‑tier semiconductor heterointerfaces. Its value is 10 times that of diamond‑Si interfaces and 2.5 times that of Si‑Ge interfaces, corresponding to extremely low interfacial thermal resistance.

• The 3C‑SiC/AlN epitaxial interface also possesses ultra‑high thermal boundary conductance, suitable for various wide‑bandgap integrated devices.

Compared with heterointerfaces fabricated by traditional bonding processes, as‑grown 3C‑SiC epitaxial interfaces feature low defect density, no foreign intermediate layers and low thermal resistance, effectively mitigating interfacial heat‑dissipation bottlenecks of heterogeneously integrated devices. Benefiting from silicon‑compatible epitaxy, high‑thermal‑conductivity 3C‑SiC can be inexpensively integrated with mature silicon‑based circuits, substantially improving heat‑dissipation efficiency and operational reliability of high‑density hybrid integrated circuits.

IV. Comprehensive Advantages and Industrialization Challenges of 3C‑SiC Materials

1. Core Comprehensive Advantages

• Outstanding bulk‑material performance: Isotropic ultra‑high thermal conductivity > 500 W/(m·K); large‑size wafers are commercially available, second only to diamond.

• Excellent electrical properties: Highest channel mobility among SiC polytypes, which significantly reduces switching and conduction losses of devices.

• Leading thin‑film performance: Ultra‑high thermal conductivity is retained even for micron‑scale thin films, compatible with miniaturized high‑power devices.

• Powerful integration capability: Epitaxial growth on silicon substrates is achievable; native heterointerfaces deliver low thermal resistance and compatibility with conventional silicon processes.

• Wide application scope: Applicable to power electronics, GaN device substrates, chip thermal management, high‑frequency radio‑frequency devices and other fields.

2. Existing Industrialization Challenges

• High process barriers: Precise control over defects such as stacking faults and dislocations is difficult for high‑quality wafers.

• Strict impurity control: Trace boron impurities can drastically degrade thermal conductivity, imposing stringent requirements on growth equipment and processes.

• Incomplete industrial chain: Commercial maturity lags behind 4H‑SiC and 6H‑SiC; further iterations are required for device reliability verification and mass‑production supporting facilities.

V. Summary and Industry Outlook

Although 4H‑SiC and 6H‑SiC remain mainstream choices in the current SiC industry, driven by trends toward high power, high density and heterogeneous integration, 3C‑SiC exhibits differentiated technical competitiveness thanks to its unique merits: superior thin‑film thermal conductivity, ultra‑low interfacial thermal resistance, silicon‑compatible integration and low power losses.
For device R&D enterprises, 3C‑SiC is no longer a niche alternative material. Instead, it serves as a core technical direction for pre‑research of next‑generation high‑end power devices, heat‑dissipation‑solution upgrading and product‑performance iteration, possessing high R&D and mass‑production value.
JXT supplies 2‑ to 12‑inch silicon carbide products, including conductive and semi‑insulating types. Customization of 3C‑SiC, 4H‑SiC and 6H‑SiC polytypes is supported to fully meet substrate‑supply demands for scientific research, device pre‑research, small‑batch sampling and mass production.