Removal of Nanoceria Abrasive Particles by Using Diluted SC1 and Non-Ionic Surfactant

Abstract

Nanoceria abrasives have received intensive attention in the process of shallow trench isolation (STI) polishing since it can result in less scratch. However, the nanoceria particles are very difficult to remove after chemical mechanical polishing. In this study, it is found that by adding AEO-20, a nonionic surfactant with appropriate concentration in the SC1 (H2O2: NH4OH: H2O = 1: 1: 5 v/v/v) and SC1 solution with diluted ratio up to 10, the nanoceria abrasive particles on the contaminated SiO2 wafers can be completely removed. Multiple measurement results show that the SC1 can react with Ce3+ and form Ce4+ in the ceria slurry, and the Ce3+ will slightly react with AEO-20 while Ce4+ will not. It is concluded that AEO-20 will adsorb on the nanoceria particles and will not change the repulsive force between ceria and SiO2. The adsorbed surfactant will lift the particles off the SiO2 surface while the slight reaction between AEO-20 and Ce3+ will accelerate the lift-off process.