3C-SiC Wafer

3C-SiC Wafer technology is a breakthrough in the traditional production of Silicon Carbide wafers, effectively improving efficiency and reducing costs.Semixlab owns the core technology, using hydrophilic bonding or plasma-activated bonding, to ensure that the interface is free of gas bubbles and the bonding strength is high. A single donor wafer can be reused more than 10 times, reducing the cost of 3C-SiC substrate by more than 50%. Support substrate adopts low resistivity polycrystalline SiC (e.g., 2mΩ-cm), reducing device on-resistance (RDSon) by 24%. Compatible with large-size wafers: supports mass production of 200mm wafers, breaking through the traditional 3C-SiC wafer size limitations (usually ≤150mm).

The application of Smart-Cut technology in the manufacture of 3C-SiC wafer substrate is explained in detail

Technical background and core principles

Smart-Cut technology was proposed by the Soitec company in the 1990s, initially used to manufacture SOI (silicon-on-insulator) wafers, and gradually expanded to the field of Silicon carbide (SiC), especially the optimization of 4H-SiC substrates. The core principle is to realize the transfer of ultra-thin single crystal layer by hydrogen ion implantation and wafer bonding, so as to solve the problem of high cost and low yield of traditional SiC substrate.

The particularity of 3C-SiC: 3C-SiC (cubic silicon carbide) is a polytype of SiC, with a cubic crystal structure, compared with 4H-SiC (hexagonal structure), its growth difficulty is higher and the defect density is greater. Therefore, Smart-Cut technology needs to be adapted to the physical characteristics of 3C-SiC.

The key steps of Smart-Cut technology in 3C-SiC

1. Donor wafer preparation

High quality 3C-SiC layers are grown by chemical vapor deposition (CVD) or physical vapor transfer (PVT) using single crystal 3C-SiC wafers as donors.

Challenges: Heteroepitaxial growth of 3C-SiC is prone to crystal defects, and growth conditions need to be optimized to reduce stacking faults.

2. Hydrogen ion implantation

The injection of hydrogen ions (H +) on the surface of the donor wafer forms a weakened layer of predetermined depth (e.g., at 1μm).

Parameter adjustment: The lattice constant of 3C-SiC is different from that of silicon, and the injected energy (e.g. 100-200 KeV) and dose (5×10¹⁶~1×10¹⁷ cm⁻²) must be adjusted to achieve efficient separation.

3. Wafer bonding

The injected donor wafer is bonded to a polycrystalline SiC or a low-cost support substrate (e.g., highly doped polycrystalline SiC).

Key technology: Using hydrophilic bonding or plasma activation bonding to ensure that the interface is bubble-free and the bonding strength is high.

4. Annealing and layer separation

After heat treatment at 400~600℃, hydrogen ions gather to form microcavities, causing the donor wafer to break along the weakened layer and transfer the ultra-thin 3C-SiC layer to the supporting substrate.

Optimization point: the thermal expansion coefficient of 3C-SiC should be matched with the support substrate to avoid stress cracks in the annealing process.

5. Surface treatment

Chemical mechanical polishing (CMP) is performed on the separated 3C-SiC layer to make the surface roughness <0.5nm to meet the epitaxial growth requirements.

Application prospect and latest progress

· Electric vehicles and energy: 3C-SiC devices have cost advantages in applications below 1200V, and Smart-Cut technology can promote their popularity in vehicle chargers and photovoltaic inverters.

· Technology breakthrough: Soitec has partnered with ST to develop Smart-Cut based 8-inch SiC wafers, which are expected to be mass-produced in 2025 and may be expanded to 3C-SiC in the future.

· Research trends: Laboratory data in 2023 show that RDSon of 3C-SiC MOSFETs using Smart-Cut can be reduced to 2.8mΩ·cm² at 650V, close to the level of 4H-SiC.

Smart-Cut technology provides a cost-effective solution for the manufacture of 3C-SiC substrates, but its practical application still needs to overcome the difficulties of crystal quality and process adaptation. With the advancement of large-size wafers and low-defect epitaxy technology, Smart-Cut is expected to become a critical path for commercial landing of 3C-SiC. Semixlab provides key technologies for 3C-SiC wafer bonding, providing very breakthrough value for cost control and commercialization of 3C-SiC wafers.

Technological advantages and challenges

Advantages:

· Improved material utilization: A single donor wafer can be reused more than 10 times, reducing the cost of 3C-SiC substrate by more than 50%.

· Performance optimization: Support substrate with low resistivity polycrystalline SiC (e.g. 2mΩ·cm) reduces device on-resistance (RDSon) by 24%.

· Compatible with large-size wafers: Support 200mm wafer mass production, breaking the traditional 3C-SiC wafer size limit (usually ≤150mm).

Challenge:

· Crystal defect control: the heteroepitaxy growth of 3C-SiC is easy to introduce stacking faults, and the epitaxy process should be optimized with
Smart-Cut technology.

· Process suitability: Hydrogen ion implantation parameters need to be re-validated for the crystal structure of 3C-SiC to avoid layer separation failures.

· Interface quality: The bonding interface must be atomically flat, otherwise the reliability of the device will be affected.