Surface compliant bonding properties of low-temperature wafer bonding using sub-micron Au particles

Compression deformation property, which is directly related to an ability of surface compliant bonding and hermetic sealing, of low-temperature wafer bonding using sub-micron Au particles was studied. Wafer bonding test using 0.3 μm particles demonstrated excellent hermeticity with He leak rate better than 1 × 10^-9 Pa·m³/s even on a substrate with a surface topography of a few μm. Cross-section SEM observation of the patterns with different particle sizes demonstrated that special voids are smaller in 0.1 μm particle patterns compared to that in 0.3 μm particle patterns. Deformation measurement revealed that 0.1μm particle patterns with initial height of 17 μm deformed by 9.4 μm after pressed at 100 MPa, which is fairly larger than that of 6.2 μm for 0.3 μm Au particles. This result can indicate that patterns with smaller size Au particles can be hermetically bonded at lower applied pressure.