Diamond Heat Sink Submounts and Diamond Substrates for Ga₂O₃ and AlN Power Chips: Applications and Specifications

Core Distinction: Single/Polycrystalline Diamond Heat Sink Sheets Directly Bonded Beneath Ga₂O₃ and AlN Epitaxial Wafers; Polycrystalline Diamond Epitaxy Grown Directly on Substrates (Ga₂O₃, AlN)

I. Diamond Heat Sink Sheets (Predominantly Single/Polycrystalline CVD)

Applications

1. Gallium Oxide (Ga₂O₃) Power Chips Ga₂O₃ features extremely low intrinsic thermal conductivity (≈9 W/mK). Joule heat in high-voltage devices readily induces thermal breakdown. Diamond heat sink sheets are directly bonded to the backside of Ga₂O₃ wafers for wafer-level heat spreading, rapidly extracting heat from hotspots to water-cooled/microchannel substrates. Suitable for discrete high-voltage diodes, power MOSFETs and high-voltage switches.

Characteristics: Simple process with moderate interfacial thermal resistance; directly mitigates heat buildup within Ga₂O₃.

2. Aluminum Nitride (AlN) Power Chips (AlN-based Power/RF Devices) AlN devices exhibit superior thermal conductivity compared to Ga₂O₃. Nevertheless, ultra-high heat flux occurs under high-frequency, high-power operating conditions (deep ultraviolet, high-voltage RF). Diamond heat sinks serve as backside bonded carriers for AlN wafers to reduce junction temperature, boost power density and reliability; deployed for thermal management of AlN thin-film devices.

Specifications (Single/Polycrystalline CVD Heat Sink Sheets)

• Thermal conductivity: 1600–2200 W/m·K

• Dimensions: Square chips: 10×10 mm, 15×15 mm, 20×20 mm; wafers: 2/4/6 inch, custom dicing available

• Thickness: 100 μm, 200 μm, 300 μm, 500 μm (200–300 μm commonly used)

• Surface polishing: Single-sided CMP, Ra＜1 nm

• Resistivity: ＞10¹³ Ω·cm, electrically insulating to avoid device leakage

• CTE: 1.0×10⁻⁶/K, lowering thermal stress between diamond and the chip

II. Diamond Thin Films (High-thermal-conductivity Polycrystalline CVD)

Applications

1. Gallium Oxide (Ga₂O₃) Power Chips (Diamond-on-Ga₂O₃ Heterogeneous Integration) Polycrystalline diamond thin films are directly grown on β-Ga₂O₃ substrates. Heat generated by device hotspots conducts straight into the ultra-high thermal conductivity polycrystalline diamond film, drastically cutting interfacial thermal resistance at the source. Compared with Ga₂O₃ on sapphire/SiC, junction temperature reduction can reach over 100 °C. Targeted for ultra-high-power, high-current-density Ga₂O₃ RF/power devices. Currently at pilot and sample validation stage with high industrialization barriers.

2. Aluminum Nitride (AlN) Power Chips (Diamond-on-AlN) Polycrystalline diamond thin films are grown on AlN substrates, where diamond acts as the high-thermal-conductivity film. AlN functions simultaneously as the barrier/buffer layer for deep-UV devices and high-frequency AlN-based power devices. This addresses the thermal conductivity limitation of bare AlN substrates; presently at cutting-edge R&D sample stage.

Specifications (Diamond Substrate Wafers, Epitaxy-Grade)

1. Thermal conductivity: 1200–1600 W/m·K

2. Dimensions: Mainly 1 inch, 2 inch, 4 inch and 6 inch R&D sample wafers

3. Thickness: 300–500 μm

4. Surface polishing: Single-sided ultra-precision CMP, Ra＜1 nm

5. Lattice quality: Surface cleanliness meets requirements for polycrystalline diamond growth

6. Resistivity: Insulation grade to prevent device leakage