  Overheating has emerged as a primary challenge constraining the reliability
and performance of next-generation high-performance electronics, such as
chiplets and (ultra)wide bandgap electronics. Advanced heterogeneous
integration not only constitutes a pivotal technique for fabricating these
electronics but also offers potential solutions for thermal management. This
study presents the integration of high thermal conductivity semiconductors,
specifically, 3C-SiC thin films and diamond substrates, through a
room-temperature surface-activated bonding technique. Notably, the thermal
conductivity of the 3C-SiC films is among the highest for all semiconductor
films which can be integrated near room temperature with similar thicknesses.
Furthermore, following annealing, the interfaces between 3C-SiC and diamond
demonstrate a remarkable enhancement in thermal boundary conductance (TBC),
reaching up to approximately 300%, surpassing all other grown and bonded
heterointerfaces. This enhancement is attributed to interfacial reactions,
specifically the transformation of amorphous silicon into SiC upon interaction
with diamond, which is further corroborated by picosecond ultrasonics
measurements. Subsequent to annealing at 1100 C, the achieved TBC (150 MW/m2-K)
is record-high among all bonded diamond interfaces. Additionally, the
visualization of large-area TBC, facilitated by femtosecond laser-based
time-domain thermoreflectance measurements, shows the uniformity of the
interfaces which are capable of withstanding temperatures as high as 1100 C.
Our research marks a significant advancement in the realm of thermally
conductive heterogeneous integration, which is promising for enhanced cooling
of next-generation electronics.
