SiC-on-Insulator SiCOI Substrates High Thermal Conductivity Wide Bandgap

Introduce

Silicon Carbide on Insulator (SiCOI) thin films​​ are innovative composite materials, typically fabricated by depositing a single-crystal, high-quality silicon carbide (SiC) thin layer (500–600 nm, depending on specific applications) onto a silicon dioxide (SiO₂) substrate. SiC is renowned for its exceptional thermal conductivity, high breakdown voltage, and outstanding chemical resistance. When combined with an insulating layer, this material can simultaneously meet the demanding requirements of high-power, high-frequency, and high-temperature applications.

Principle

The fabrication of SiCOI thin films can be achieved using CMOS-compatible processes such as ​​ion cutting​​ and ​​bonding​​, thereby enabling seamless integration with existing electronic circuits.

Ion - cutting Process
One of the processes is based on ion - cutting (Smart Cut) and SiC layer transfer, followed by wafer bonding. This technique has been applied to the large - scale production of silicon - on - insulator (SOI) wafers. However, in SiC applications, ion implantation may introduce damage that cannot be recovered by thermal annealing, resulting in excessive losses in photonic structures. Additionally, high - temperature thermal annealing exceeding 1000°C is not always compatible with certain process requirements.

To address these issues, grinding and chemical mechanical polishing (CMP) techniques can be used to directly thin the bonded SiC/SiO₂ - Si stack to <1 μm, achieving a smooth surface. Further thinning can be achieved via reactive ion etching (RIE), which minimizes losses in SiCOI structures. Moreover, wet oxidation - assisted CMP has been proven to effectively reduce surface roughness and scattering losses, while high - temperature annealing can further optimize wafer quality.

Wafer Bonding Technology
Another preparation method is wafer bonding technology, which involves applying pressure between silicon carbide (SiC) and silicon (Si) wafers and utilizing the thermal - oxidation layers of the two wafers for bonding. However, the thermal - oxidation layer of SiC may cause local defects at the SiC - oxide interface. These defects may lead to an increase in optical loss or the formation of charge traps. In addition, the silicon dioxide layer on SiC is usually prepared by plasma - enhanced chemical vapor deposition (PECVD), and this process may also bring about certain structural problems.

To overcome the above challenges, a new 3C - SiCOI chip manufacturing process has been proposed, which adopts an anodic bonding process combined with borosilicate glass, thus preserving all the functions of silicon micromachining/CMOS and SiC photonics. In addition, amorphous SiC can also be directly deposited on the SiO₂/Si wafer by PECVD or sputtering, thus achieving simplified process integration. All these methods are fully compatible with CMOS processes, further promoting the application of SiCOI in the field of photonics.

Advantages
Compared with the existing material platforms of silicon - on - insulator (SOI), silicon nitride (SiN), and lithium niobate - on - insulator (LNOI), the SiCOI material platform demonstrates significant advantages in optical applications and is emerging as the next - generation material platform for quantum technology. The specific advantages are as follows:

• It exhibits excellent transparency in the wavelength range from approximately 400 nm to approximately 5000 nm and achieves outstanding performance with a waveguide loss of less than 1 dB/cm.
• It supports multiple functions such as electro - optic modulation, thermal switching, and frequency tuning.
• It shows second - harmonic generation and other nonlinear optical characteristics and can serve as a single - photon source platform based on color centers.

​Applications

In addition, SiCOI combines the advantages of silicon carbide (SiC) in high thermal conductivity and high breakdown voltage with the good electrical isolation properties of insulators, and enhances the optical properties of the original SiC wafer. It is widely used in high - tech fields such as integrated photonics, quantum optics, and power devices. Based on this material, researchers have developed a large number of high - quality photonic components, including linear waveguides, microring resonators, photonic crystal waveguides, microdisk resonators, electro - optic modulators, Mach - Zehnder interferometers (MZIs), and beam splitters. These components feature low loss and high performance, providing a solid technical foundation for quantum communication, photonic computing, and high - frequency power devices.


Silicon Carbide on Insulator (SiCOI) thin films​​ are innovative composite materials, typically fabricated by depositing a single-crystal, high-quality silicon carbide (SiC) thin layer (500–600 nm, depending on specific applications) onto a silicon dioxide (SiO₂) substrate. SiC is renowned for its exceptional thermal conductivity, high breakdown voltage, and outstanding chemical resistance. When combined with an insulating layer, this material can simultaneously meet the demanding requirements of high-power, high-frequency, and high-temperature applications.

Q&A

Q1: What is the difference between SICOI and traditional SiC - on - Si devices?​​
​​A​​: SICOI's insulator substrate (e.g., Al₂O₃) eliminates parasitic capacitance and leakage currents from silicon substrates while avoiding defects caused by lattice mismatch. This results in superior device reliability and frequency performance.

​​Q2: Can you provide a typical application case of SICOI in automotive electronics?​​
​​A​​: Tesla Model 3 inverters use SiC MOSFETs. Future SICOI - based devices could further enhance power density and operating temperature ranges.

​​Q3: What are the advantages of SICOI compared to SOI (silicon - on - insulator)?​​
​​A​​:

• ​​Material Performance​​:SICOI's wide bandgap enables operation at higher power and temperatures, whereas SOI is limited by hot carrier effects.
• ​​Optical Performance​​:SICOI achieves waveguide losses of <1 dB/cm, significantly lower than SOI's ~3 dB/cm, making it suitable for high - frequency photonics.
• ​​Functional Expansion​​:SICOI supports nonlinear optics (e.g., second - harmonic generation), while SOI relies primarily on linear optical effects.

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