Development of face-to-face and face-to-back ultra-fine pitch Cu-Cu hybrid bonding

We have developed the novel fabrication process that has realized the robust ultra-fine pitch, 1 μm pitch, wafer level face-to-face Cu-Cu hybrid bonding. For the stable electrical connection between upper Cu pads and lower Cu pads, wet process, ECD process and CMP process were examined to protrude Cu connection pads steadily and we have verified that our advanced process integration has achieved high electrical yields. Moreover, the 1.4μm pitch level Cu-Cu hybrid bonding has been successfully introduced into face-to-back bonding interface. We have developed the novel wafer thinning process to minimize total thickness variation (TTV) of Si and roundness of wafer edge, at the same time.