Development of novel multi-selective slurry with mechanically driven etching for through silicon via chemical mechanical polishing

Abstract

As a new generation of semiconductor chips such as 3D integration has been developed, the circuit becomes diverse and fine with the composition of various materials. In this study, the novel multi-selective slurry was developed to control each material removal of SiO2, Si3N4, and Cu films respectively. The material removal rate (MRR) of SiO2 was chemically controlled using tetrabutylammonium fluoride (TBAF), in which the addition of 0.5 mM of TBAF increases the MRR of only SiO2 film by 16 times larger than pristine silica slurry without any side effect on the MRR of other materials. The MRR of the Si3N4 wafer was mostly influenced by mechanical abrasion owing to the solid contents. The MRR of the Cu wafer was adjusted by varying the amount of benzotriazole added as an inhibitor. Because each additive affected the material removal only for the target film, the MRR for various materials could be selectively adjusted. Finally, the dishing or protrusion of Cu pad in through-silicon via (TSV) could be controlled in a nanometer scale by using a fabricated multi-selective slurry. In addition, a completely flat surface was obtained when TSV wafer was polished by the selectivity of 1:1:1 on Si3N4, SiO2, and Cu films.