[21p-P17-1~26] 13.4 Si wafer processing /Si based thin film /MEMS/Integration technology

[21p-P17-11] Hermetic Bonding on Non-flat Wafers using Planarized Electroplated Gold Bumps

〇HIDEKI HIRANO¹, KOUSUKE HIKICHI², SHUJI TANAKA¹ (1.Tohoku Univ., 2.Technofine)

Keywords:metal-bonding,planarization,intgration

Wafer-level vacuum sealing and electrical interconnection are often critical for microelectromechanical systems (MEMS). We have developed a packaging and integration technology, which is applicable to non-planer (i.e. microstructured) and temperature-sensitive wafers by means of single-point diamond fly cutting of electroplated Au bumps and Au-Au diffusion bonding. Depth of residual scratches on planarized Au bump surface are decreased by optimizing fly cutting condition. Because collapse of Au bump is strongly depending on bonding pressure, high pressure (>200 MPa) is applied for the wafer bonding process employing narrower bump. Bonding strength is improved by aid of additional bonding bump inside. Finally, more than 100 MPa bonding strength with almost 100% of hermetic sealing yield is achieved using optimal bonding process and bump design.