Low temperature bonding using sub-micron Au particles for wafer-level MEMS packaging

In this study, low temperature bonding using sub-micron Au particles was investigated. Two types of Au particles with different average mean diameter of 0.1 μm and 0.3 μm were used. The 0.1 μm Au particles were sintered at lower temperature than that of 0.3 μm. These particles have an advantage of low sintering temperature under 200 °C, and compensating surface roughness. The compression deformation properties of Au particles were measured. They were compressed to around 3 and 5 μm at 30 and 100 MPa applied pressure, respectively. Chip-level bonding was performed with sealing rings of Au particles. The tensile strength of 55.2 MPa was obtained by bonding under applied pressure of 50 MPa at 100 °C. As the evaluation of hermeticity, gross leak test was performed for bonded chips with single, double, and triple sealing rings.