Yield and Strength of Metal Wafer-Level MEMS Device Sealing Using Al, Au, or Ti
Authors: K. Schjølberg-Henriksen, PhD; E. Poppe, A.S. Moen, and E. Fasting Company: SINTEF ICT, MiNaLab, and Oslo and Akershus University College of Applied Sciences Date Published: 11/5/2012
IWLPC (Wafer-Level Packaging)
Abstract: Metal-based wafer-level bonding seems well suited for hermetic wafer-level packaging at low cost. We have compared the performance of Au-Au thermocompression bonding, Al-Al thermocompression bonding, and Ti-Si bonding, applying the same test wafer design for all three processes. Device yield, bond strength, and electric resistance of the bond were investigated. Both Au-Au and Al-Al thermocompression bonded wafers had a yield of 100%. The yield from Ti-Si bonded wafers was significantly lower. Au-Au and Al-Al bonds had bond strengths above 30 MPa and ranging as high as 159 MPa. Ti-Si bonds had strengths between 13 and 23 MPa. The electrical resistance of the bond seal was similar for all investigated bonds. The current study indicates that Au-Au hermocompression bonding and Al-Al thermocompression bonding are well suited for wafer-level packaging of MEMS devices in industrial production, while Ti-Si bonding seems less well suited.
MEMS packaging, wafer-level sealing, metal bonding