Development of a Copper Chemical Mechanical Polishing Slurry at Neutral pH Based on Ceria Slurry

Abstract

We investigated the applicability of ceria-based copper (Cu) chemical mechanical polishing slurry based on commercial ceria slurry, which contained the anionic dispersing agent. Through the zeta-potential and particle size measurements, the neutral pH condition was verified to be favorable to maintain the dispersion stability and glycine was selected as a main complexing agent. Cu polish rate tests with varying glycine concentrations and solid contents of ceria were performed and the possible reaction mechanisms were discussed. Variation in the concentration with a fixed amount of glycine affected the maximum polishing rate, whereas variation in the glycine concentration changed the concentration that resulted in the maximum polishing rate. The relationship between Cu oxide thickness and the polishing rate was investigated using coulometric reduction method analysis and X-ray photoelectron spectroscopy analysis. Surface improvement was successfully achieved with the addition of 5-aminotetrazole. According to these experiments, suggestions for ceria-based Cu slurry formulations that have high Cu removal rates and smooth polished surfaces are provided.