A Mechanistic Analysis of Oxidation-Induced Defects During Tungsten CMP: Interactions of Process, Material, and Environmental Factors

Abstract Tungsten has become widely employed as a contact metal in semiconductor devices due to its favorable material properties and process compatibility, with chemical mechanical polishing (CMP) being a crucial step in W contact formation. In this study, oxidation-induced bridge defects which occurred after tungsten CMP were characterized with optical metrology, electron microscopy, EDX, and electrical test measurements. To understand the mechanism of defect formation, the effect of CMP slurry composition, humidity, as well as dielectric material composition was investigated, leading to the elucidation of a mechanism involving a two-step corrosion of W accelerated by dielectric-induced galvanic corrosion. A multipronged strategy to address the root causes achieved the near elimination of the defects, illustrating the value of the mechanistic analysis.