Study on the effect of residual ceria slurry on chemical mechanical planarization (CMP)

Abstract

The effect of residual ceria slurry on a pad was investigated to improve the cleaning efficiency while maintaining the removal rate of chemical mechanical planarization (CMP). This combined process consists of two sequential steps: polishing with slurry, then polishing with residual slurry and cleaning with deionized water (DIW). Ceria slurry injected in the first step is used for polishing, while the rest of the ceria slurry remains in the groove or escapes out of the pad. When DIW is injected in the second step, the ceria slurry nanoparticles remaining on the pad participate in polishing, and DIW cleans the wafer surface, preventing contamination. The most efficient ceria injection time uses this two-step process, and the cleaning efficiency for this optimized time was confirmed. With optimal process conditions, particle area ratio decreased from 9.035% to 0.839%, indicating increased cleaning efficiency. This study suggests the time needed for the slurry to attain efficient polishing and demonstrates a method for shortening the ceria process time by simultaneously polishing and cleaning during the CMP process.