Surface co-hydrophilization via ammonia inorganic strategy for low-temperature Cu/SiO2 hybrid bonding

1.Introduction During massive data movements in digital computing systems,several issues have emerged such as high latency,energy ineffi-ciency,and low bandwidth due to the physical separation of pro-cessor and memory units(so-called memory wall)[1-3].To miti-gate the data-movement limitations,three-dimensional(3D)chip integration becomes an optimal solution within von Neumann ar-chitecture since the dense vertical interconnections shorten the distance between chips[4,5].However,the extensively used micro solder bumps for 3D chip stacking impede the further improve-ment of interconnection pitch(＜10 μm).In this scenario,the Cu/SiO2 hybrid bonding technology came into being.Owing to the coexistence of planarized Cu connections and SiO2 layers,Cu/SiO2 hybrid bonding is the desirable enabler of submicron ultra-dense integration(＜1 μm),which benefits from Cu-Cu and SiO2-SiO2 homogeneous direct bonding replacing micro bumps and underfill[6,7].