Microwave Journal
www.microwavejournal.com/articles/29542-fujitsu-technology-bonds-single-crystal-diamond-sic-at-room-temperature

Fujitsu Technology Bonds Single-Crystal Diamond, SiC at Room Temperature

December 18, 2017

Fujitsu Limited and Fujitsu Laboratories Ltd. announced development of the world's first technology for bonding single-crystal diamond to a silicon carbide (SiC) substrate at room temperature. Using this technology for heat dissipation in a high-power GaN high electron-mobility transistor (HEMT) enables stable operations at high-power levels. Application of this technology is expected to significantly enhance the performance of weather radars and wireless communications.

Boosting range and power in radar and wireless communications also increases the heat produced by devices, which adversely affects their performance and reliability. This creates a need to efficiently carry device heat to a cooling structure. Single-crystal diamond is known to have good thermal conductivity, but with existing technologies, the argon (Ar) beams used to remove impurities in the manufacturing process create a low-density damaged layer on the surface, which weakens bonding strength. Also, bonding with an insulating film such as silicon nitride (SiN) impairs thermal conductivity due to SiN's thermal resistance.

Now, by protecting the surface of the diamond with an extremely thin metallic film, Fujitsu and Fujitsu Laboratories succeeded in preventing the formation of the damaged layer and bonding single-crystal diamond to a SiC substrate at "room-temperature bonding." Simulations using actual measurements of thermal parameters have confirmed that devices using this technology would lower thermal resistance to 61 percent of existing ones.

This technology promises GaN-HEMT power amps for transmitters to operate at higher power, and increase the observable range by roughly 1.5x when applied to systems such as weather radar.

This research was conducted in part with support from the Innovative Science and Technology Initiative for Security, established by the Acquisition, Technology & Logistics Agency (ALTA), Japan Ministry of Defense.