Characterization of Circulated Chemical-Mechanical Polishing Slurry Particles Using Two Analysis Methods
Mark R. Litchy and Donald C. Grant
CT Associates, Inc., 10777 Hampshire Ave. S., Bloomington, MN 55438
Kristi Nicholes and Rakesh K. Singh
BOC Edwards, Chemical Management Division, 322 Lake Hazeltine Dr., Chaska, MN 55318
This study investigated changes in particle size distributions (PSDs) of two chemical-mechanical polishing (CMP) slurries circulated in a simulated distribution loop. The slurries contained submicron (0.02- 0.20 ?m) silica or alumina particles at concentrations greater than 1014/ml. They also contained relatively small concentrations of large particles (105– 109/ml, ? 0.5 ?m), which can adversely affect microfabrication CMP processes. Understanding and eliminating sources of large particles is essential for designing successful CMP processes and slurry handling equipment.
Samples of large particles from as-received and circulated slurry were analyzed to determine particle concentration, size, shape and elemental composition using Scanning Electron Microscopy/Energy- Dispersive X-Ray (SEM/EDX) spectroscopy and optical particle counting (OPC). Although the SEM and OPC techniques did not agree in terms of absolute concentrations, the relative changes in the PSDs after circulation were similar. Large particle concentrations in the silica slurry increased after circulation, while little change was observed in the alumina slurry. The supermicron particles in all slurry samples appeared to be agglomerates of submicron particles.
CTA publication #42: in Proceedings of ECS International Semiconductor Technology Conference 2000, Shanghai, China, May 2001