Cu/adhesive hybrid bonding through a Cu-first bonding approach by using H-containing HCOOH vapor surface treatment

Cu/adhesive hybrid bonding is a promising technology to fabricate 3D integrated microsystems with ultra-fine pitch and short vertical interconnects, low electrical resistance, and high reliability. The main remaining issues of this technology include bonding temperature mismatch between Cu-Cu (350–400 °C) and adhesive (typically ≤250 °C), long thermal-compression time (low throughput), and high thermal stress. In this paper, we present a sub-200 °C Cu/adhesive hybrid bonding method. By using H-containing HCOOH vapor pre-bonding treatment, the bonding temperature is lowered to 180–200 °C and the thermal-compression time is shortened to 600 s, enabling a Cu-first hybrid bonding approach. Cu/adhesive hybrid bonding was successfully demonstrated at bonding temperature of 180 °C. The effects of prebonding treatment temperature and time on Cu-Cu bonding and cyclo-olefin polymer (COP) adhesive bonding are investigated in detail.

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