4H-SiC wafer bonding has been achieved by the modified surface activated bonding (SAB) method without any chemical-clean treatment and high temperature annealing. Strong bonding between the SiC wafers with tensile strength greater than 32 MPa was demonstrated at room temperature under 5 kN force for 300 s. Almost the entire wafer has been bonded very well except a small peripheral region and few voids. The interface structure was analyzed to verify the bonding mechanism. It was found an amorphous layer existed as an intermediate layer at the interface. After annealing at 1273 K in vacuum for 1 h, the bonding tensile strength was still higher than 32 MPa. The interface changes after annealing were also studied. The results show that the thickness of the amorphous layer was reduced to half after annealing.

In this study, the results of direct wafer bonding of SiC–SiC at room temperature by standard surface-activated bonding (SAB) and modified SAB with a Si-containing Ar ion beam were compared, in terms of bonding energy, interface structure and composition, and the effects of rapid thermal annealing (RTA) at 1273 K in Ar gas. Compared with that obtained by the standard SAB, the bonding interface obtained by the modified SAB with a Si-containing Ar ion beam is ∼30% stronger and almost completely recrystallized without oxidation during RTA, which should be due to the in situ Si compensation during surface activation by the Si-containing Ar ion beam.

A modified surface activated bonding (SAB) with Fe–Si multi-nanolayers is expected to achieve the wafer bonding of SiC to various materials. However, Fe diffusion, which affects device performance, cannot be avoided during some annealing processes. In this work, the room-temperature wafer bonding of SiC–Si by only one sputtered Si nanolayer was successfully achieved. The bonding interface was investigated. A uniform intermediate layer with a thickness of ∼15 nm just containing Si, C, and Ar was found at the interface. The bonding strength between the SiC surface and the sputtered Si nanolayer could reach the bulk Si strength in accordance with the results of the strength test. This indicates that the wafer bonding of SiC to any other materials can be achieved easily if the material could be also strongly bonded to the sputtered Si nanolayer. In addition, the thermal and chemical reliabilities of the SiC–Si bonding interface were investigated by rapid thermal annealing and KOH etching, respectively.

Although the monolithic integration of silicon carbide (SiC) Micro-Electro-Mechanical Systems (MEMS) and SiC electronics is very promising, it is still very challenging due to the absence of suitable bulk machining technology of SiC. In this research, wafer bonding was proposed to assist the monolithic integration of SiC MEMS and SiC electronics by the formation of a suspended epitaxial SiC membrane. However, currently, SiC-SiC wafer bonding is still very difficult, especially for its direct wafer bonding. Surface activated bonding (SAB) method was applied to realize the direct wafer bonding of SiC-SiC at room temperature. The bonding energy of ∼1.4 J/m2 was obtained without orientation dependence. Correspondingly, the tensile strength of bonding interface is ∼12.2 MPa and could be improved by rapid thermal annealing to the values higher than 21.6 MPa. The bonding mechanisms were investigated through Monte Carlo simulation, interface analysis by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX), and in-situ analysis on the activated SiC surfaces by X-ray photoelectron spectroscopy (XPS).

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