Breaking the Power Bottleneck: Technical Path of Diamond Heat Sink Substrates Empowering Thermal Management of Photonic

As the requirements for power density of photonic chips in fields such as 5G communications and quantum computing exceed 500 W/cm², traditional aluminum nitride (AlN) and copper-based heat sinks are approaching their performance limits. Data shows that for every 10℃ rise in the junction temperature of a photonic chip, its reliability drops by 50% and the modulation bandwidth attenuates by 15%. As the material with the highest thermal conductivity in nature, diamond has a room-temperature thermal conductivity of up to 2200 W/(m·K), which is 5 times that of copper and more than 10 times that of AlN. Moreover, its coefficient of thermal expansion (1.1 ppm/K) is highly matched with Ⅲ-Ⅴ group semiconductors (InP/GaAs), which can effectively suppress interface delamination caused by thermal stress. In addition, diamond features a broad optical transmission window (225 nm to far infrared) and chemical inertness, enabling direct integration in the active region of photonic chips and avoiding optical loss and environmental corrosion issues.

Interface Matching and Packaging Integration Technology

Thermal Resistance Optimization Solutions

Metallization layer design: A composite structure of Ti (adhesion layer)/Pt (diffusion barrier layer)/Au (bonding layer) is adopted, reducing the interfacial thermal resistance to below 5×10⁻⁵ m²·K/W.

Buffer layer technology: A nanodiamond-titanium alloy gradient layer is introduced between the diamond and the chip, increasing the bonding strength to 200 MPa and solving the problem of lattice mismatch.

Precision Processing Technology

Laser micro-nano processing: Femtosecond laser stealth dicing technology is used to realize the processing of complex special-shaped structures, with an efficiency 15 times that of traditional processes and edge chipping controlled within 2 μm.

Polishing optimization: Combining chemical mechanical polishing (CMP) with sacrificial layer technology, the surface roughness Ra ≤ 0.05 μm and the thickness tolerance is ±1.5 μm, meeting the requirements of chip-level packaging.

Composite Heat Sink Architecture Design

For cost-sensitive scenarios, a "diamond microchip + hybrid substrate" architecture is adopted: a 150-500 μm thick diamond layer is integrated in the core heating area, and AlN or copper-based materials are used in the peripheral area. This design reduces the cost by 40% compared with all-diamond heat sinks while maintaining a thermal conductivity of ≥1400 W/(m·K). Verified in photonic chips for automotive LED headlights, it reduces the junction temperature by 40℃ and the light attenuation rate by 60%.

High-Power Laser Diodes

Diamond heat sinks are integrated with InP laser chips through Au-Sn low-temperature bonding (280℃), increasing the output power from 5 W to 18 W and extending the service life to over 10⁴ hours, meeting the requirements of 100 Gbps optical modules. The key technology lies in the precise alignment (deviation ≤ 5 μm) between the heat sink and the active region of the chip to achieve vertical heat conduction.

Quantum Photonic Chips

Utilizing the quantum state characteristics of diamond color centers, single-photon sources and waveguide structures are integrated on the heat sink substrate: NV⁻ color centers are prepared by ion implantation technology, and real-time heat dissipation of the heat sink extends the quantum state coherence time to 2 ms, providing a stable working environment for quantum key distribution (QKD) chips. This solution has been applied in quantum communication terminals, increasing the key generation rate by 3 times.

3D Packaged Photonic Chips

To address the hot spot issue of 3D packaged photonic chips, an embedded diamond heat dissipation layer is adopted. Through the coupled design of microchannels and heat sinks, the temperature difference of hot spots is reduced from 30℃ to 8℃, and the fluctuation rate of computing power output is decreased by 70%. Its core is the compatible processing of diamond and through-silicon vias (TSVs), realizing uniform on-chip global heat dissipation.

With its extreme thermal performance and integration compatibility, diamond heat sinks have become a core supporting technology for breaking the power density limit of photonic chips. As the cost of CVD preparation continues to decline (the cost of single-crystal diamond heat sinks is expected to drop by 30% in 2026) and processing technologies mature, their applications will expand from high-end optical modules to automotive photonic chips, quantum sensors and other fields in an all-round way, driving the evolution of optoelectronic devices toward higher power, higher reliability and smaller size.

CSMH uses the MPCVD method to prepare large-sized and high-quality diamonds,and currently has mature products such as diamond heat sinks, diamond wafers, diamond windows,diamond composite materials,etc.Among them,the thermal conductivity of diamond heat sinks is 1000-2200w/（m.k）, which has been applied in aerospace, high-power semiconductor lasers, optical communication, chip heat dissipation, nuclear fusion and other fields.