Wafer-On-Wafer-On-Wafer (WoWoW) Integration Having Large-scale High Reliability Fine 1 μm Pitch Face-To-Back (F2B) Cu-Cu Connections and Fine 6 μm Pitch TSVs

Wafer-on-wafer-on-wafer integration, consisting of three device wafers, is a key concept that accelerates the evolution of stacked devices. We have successfully developed Wafer-On-Wafer-On-Wafer integration technologies which consist of 1 μm pitch Face-To-Face and Face-To-Back Cu-Cu connections and 6 μm pitch TSVs processes having large-scale of 50,000 links, good connectivity, and high reliabilities for the first time. Nicely aligned and bonded Cu pads are observed at Face-To-Face and Face-To-Back bonding each interface. Each connectivity of the 3D components: Face-To-Face, Face-To-Back Cu-Cu connections and TSVs, was quantitatively discussed with electrical resistance data. The TSVs proximity effects in Wafer-on-wafer-on-wafer integration were investigated by employing silicon resistor formed on the middle wafer frontside to discuss the effect of Face-To-Back Cu-Cu hybrid bonding.