3차원 소자 적층을 위한 BOE 습식 식각에 따른 Cu-Cu 패턴 접합 특성평가

Three-dimensional integrated circuit (3D IC) technology has become increasingly important due to the demand for high system performance and functionality. We have evaluated the effect of Buffered oxide etch (BOE) on the interfacial bonding strength of Cu-Cu pattern direct bonding. X-ray photoelectron spectroscopy (XPS) analysis of Cu surface revealed that Cu surface oxide layer was partially removed by BOE 2min. Two 8-inch Cu pattern wafers were bonded at 400℃ via the thermo-compression method. The interfacial adhesion energy of Cu-Cu bonding was quantitatively measured by the four-point bending method. After BOE 2min wet etching, the measured interfacial adhesion energies of pattern density for 0.06, 0.09, and 0.23 were 4.52 J/m2, 5.06 J/m2 and 3.42 J/m2, respectively, which were lower than 5 J/m2. Therefore, the effective removal of Cu surface oxide is critical to have reliable bonding quality of Cu pattern direct bonds.