300 μm Deep through silicon via in laser-ablated CMOS multi-project wafer for cost-effective development of integrated MEMS

This study has opened a possibility to fabricate through silicon vias (TSV) in a LSI wafer available by commercial multi-project wafer (MPW) service and integrate the LSI and MEMS by wafer bonding. 300 μm deep Cu annular type TSV were fabricated in a TSMC 0.18 μm CMOS LSI MPW cut into 4" diameter. The developed TSV process managed mechanically fragile property of the laser-ablated MPW by low stress TEOS PECVD SiO2 backfilling, surface planarization, temporally wafer support etc. The LSI and MEMS were integrated by Au-Au thermocompression bonding at 300°C, and the completed device worked via the TSV as designed. “Tohoku TSV CMOS-MEMS platform” presented in this paper gives many chances for cost-effective development of surface-mountable CMOS-integrated MEMS.