Characterization direct bonding of SiC/SiN layer on Si wafer for MEMS capacitive pressure sensor

Two silicon wafer size of 2.5 mm × 2.5 mm with 1 μm LPCVD silicon carbide (SiC) and 200 nm LPCVD silicon nitride, respectively has been characterize direct bonding between silicon nitride and silicon carbide surfaces. Chemical-mechanical polishing (CMP) treatment processes were performed to reduce the surface roughness of both surfaces before the surface are bonded to each other. The surface roughness shows about 1 μm before CMP treatment, while the smoothness of the surface roughness values as low as 20 nm was obtained after CMP treatment as measured by infinite focus microscopy (IFM). The interface between SiC/SiN layers on Si wafer was inspected by scanning electron microscopy (SEM). Heat treatment with different annealing temperatures is indentified that an optimized annealing process was at 400 °C for 2 hours to allow the bond-forming interface between silicon nitride and silicon carbide surfaces being bonded at 8.3467 MPa.