Single-Crystal and Polycrystal SiC Bonding for Cost-effective Chip Fabrication

High-quantity single-crystal silicon carbide (SiC) is widely used in power electronics due to its excellent breakdown electric field strength and high thermal conductivity. However, back grinding during the chip fabrication generally results in ≈70% of single-crystal SiC being wasted, leading to the high cost of SiC chips. In order to improve the utilization, single-crystal SiC on polycrystal SiC (SoP-SiC) is bonded. The challenge to achieve excellent bonding interfaces for such a system is the heterogeneous surface of polycrystals in which those grains with different orientations usually have different physical and chemical properties, making it difficult to achieve sufficiently smooth surfaces for bonding. Here, ion beam etching (IBE) is employed to activate the surface of polycrystal and single-crystal SiC and achieve high bonding strength (up to ≈20 MPa) after annealing in the atmosphere. Sub-nanometer-scale electron microscopy and energy spectroscopy analysis showing the IBE method can effectively inhibit the formation of silicon oxide at the bonding interface, which is expected to reduce the interface thermal resistance according to the phonon spectrum analysis. This study provides a novel method to fabricate single-polycrystal SiC junctions with high bonding strength and high thermal conductivity, which is valuable for the SiC industry.