Effects of wet treatment conditions and pattern densities on interfacial bonding characteristics of Cu-Cu direct bonds

摘要

Effects of both wet chemical treatments and line pattern densities on the interfacial bonding characteristics of Cu-Cu pattern direct bonds were systematically investigated. The silicon oxide (SiO_2) on a parallel Cu lines patterned wafer could be removed effectively by using a solution of buffered oxide etch and sulfuric acid (BOE/H_2SO_4) to improve the bonding quality of Cu-Cu pattern direct bonds. The Cu surface after BOE/ H_2SO_4 wet pretreatment revealed the complete removal of both the residue particles and the surface oxide layer. After BOE/H_2SO_4 wet pretreatment, the interfacial adhesion energies of 0.06, 0.09, and 0.23 pattern densities were 7.9, 4.8, and 4.1 J/m~2, respectively, where the dielectric erosion due to chemical-mechanical polishing (CMP) process with increasing pattern density significantly affected the Cu-Cu pattern direct bonding quality. Therefore, CMP planarization performance is critical for reliable Cu pattern direct bonding.