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Low-temperature wafer bonding using sub-micron gold particles was investigated. Wafer-level pattern transfer method has also been developed to enable patterning on wafers with fragile structures such as MEMS devices. Sub-micron Au particle patterns with a width of 20 μm - 60 μm and a height around 20 μm were formed on 100 mm-diameter glass wafers by means of wafer-level processing using photolithography and a slurry-filling technique, and then successfully transferred onto Si wafers in ambient atmosphere at a temperature of 150°C and an applied pressure of 20 MPa - 30 MPa. Wafer bonding was performed at 200°C, 100 MPa and exhibited a sufficient tensile strength of 45.8 MPa. A good hermeticity was also confirmed as He leak rate of <;1 × 10-9 Pa·m3/s. Compression deformation measurement was performed for patterns with different mean particle sizes of 0.3 μm and 0.1 μm and the performance on a-few-μm surface roughness absorption was demonstrated. Patterns with smaller size particles showed larger deformation, or more ability to absorb surface opography.
Date of Conference: 24-26 Oct. 2012