Influence of bonding atmosphere on low-temperature wafer bonding

The influence of bonding atmosphere was investigated for the wafer bonding at 25~200°C using a surface activated bonding method. The results of the analysis of activated Si surfaces under different vacuum background and the residual gases in vacuum before and after Ar fast atom beam irradiation is reported. Based on the analysis, bonding of Si wafers in nitrogen atmosphere is demonstrated with showing the effect of the timing of nitrogen introduction into the bonding chamber. The bonding energy of the bonded Si-Si wafer may reach 2 J/m² under the vacuum pressure of 5 × 10⁻⁵ Pa and N2 atmosphere by controlling the exposure time and the residual gas of water to less than 5 × 10⁻⁴ Pa-s. Using Au or Cu thin-films can reduce the influence of bonding atmosphere. Bond interfaces with few voids can be achieved, which is benefit on diffusion and plastic deformation of the Au or Cu thin-films.