[Paper Review] Interfacial reaction boosts thermal conductance of room-temperature integrated semiconductor interfaces stable up to 1100 C

Zhe Cheng, Xiaoyang Ji+8 more|arXiv (Cornell University)|Apr 14, 2024

Thermal properties of materialsMaterials Science3 citations

TL;DR

This study demonstrates that interfacial reactions during room-temperature surface-activated bonding of 3C-SiC thin films on diamond substrates enhance thermal boundary conductance (TBC) by up to 300%, achieving a record 150 MW/m²·K after annealing at 1100 °C. The improvement stems from the transformation of amorphous Si into SiC at the interface, confirmed by picosecond ultrasonics and uniform large-area thermoreflectance mapping.

ABSTRACT

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.

Motivation & Objective

• To address thermal management challenges in next-generation high-power and high-frequency electronics such as chiplets and (ultra)wide bandgap devices.
• To develop a heterogeneous integration method that enables high thermal conductance at the interface between semiconductors with minimal processing damage.
• To achieve stable, high-performance thermal interfaces capable of withstanding extreme temperatures up to 1100 °C.
• To understand and leverage interfacial reactions to enhance thermal boundary conductance in room-temperature bonded semiconductor systems.

Proposed method

• Utilized room-temperature surface-activated bonding to integrate 3C-SiC thin films on diamond substrates without high-temperature processing.
• Performed post-bonding annealing at 1100 °C to induce interfacial reactions between amorphous silicon and diamond, forming additional SiC.
• Employed picosecond ultrasonics to directly probe and confirm the interfacial reaction and its impact on thermal transport.
• Applied femtosecond laser-based time-domain thermoreflectance to map thermal boundary conductance across large-area interfaces with high spatial resolution.
• Measured thermal boundary conductance (TBC) quantitatively to evaluate interfacial thermal transport performance.
• Used X-ray diffraction and Raman spectroscopy to analyze structural and chemical changes at the interface post-annealing.

Experimental results

Research questions

• RQ1 Can interfacial reactions during room-temperature bonding significantly enhance thermal boundary conductance in semiconductor heterostructures?
• RQ2 What is the maximum thermal boundary conductance achievable in bonded 3C-SiC/diamond interfaces after high-temperature annealing?
• RQ3 How does the formation of SiC at the interface influence thermal transport properties in such systems?
• RQ4 To what extent is the thermal interface stable and uniform under extreme thermal conditions up to 1100 °C?
• RQ5 Can large-area, spatially resolved thermal conductance mapping confirm the uniformity and robustness of the interfacial bonding?

Key findings

• Thermal boundary conductance (TBC) of the 3C-SiC/diamond interface increased by up to 300% after annealing at 1100 °C, reaching 150 MW/m²·K.
• The TBC enhancement is attributed to the interfacial reaction converting amorphous silicon into SiC, as confirmed by picosecond ultrasonics.
• The interface remains stable and functional after annealing at 1100 °C, demonstrating exceptional thermal robustness.
• Femtosecond laser-based time-domain thermoreflectance revealed uniform thermal conductance across large areas, indicating high-quality, defect-free interfacial bonding.
• The 150 MW/m²·K TBC value is the highest reported to date for any bonded diamond-based interface.
• The 3C-SiC films exhibit among the highest thermal conductivities reported for semiconductor films integrated at near-room temperature with similar thicknesses.