Reduction of large particles in ceria slurry by aging and selective sedimentation and its effect on shallow trench isolation chemical mechanical planarization

Abstract

The effect of aging and selective sedimentation of ceria slurry on the slurry characteristics, such as the particle size distribution, the large-particle count, and the dispersion stability, and on the number of defects on the wafer surface during the shallow trench isolation (STI) chemical mechanical planarization (CMP) process was investigated. The aging time and temperature were considered as important variables giving great influence on the slurry characteristics and STI-CMP. By applying aging and selective sedimentation, the number of large particles produced by either strong agglomeration or soft flocculation in ceria slurry was successfully reduced, and the dispersion stability of the ceria particles was also improved. A CMP evaluation demonstrated that the number of defects on the wafer surface was significantly reduced, while maintaining the reasonable oxide removal rate and oxide-nitride selectivity.