Tool characterization and optimization was performed on a Westech Model 372 Polisher. A Rhodes ESM-U pad with a #5 groove with PSA and two slurries: a Rodel Klebosol 1501-50 silica based slurry and a proprietary cerium oxide slurry were utilized. Initial polishing of blanket thermal oxide wafers on the Westech produced %WIWNU greater than 80% using the Klebosol slurry. Following tool calibrations and modifications to machine configurations, %WIWNU dropped to approximately 5%. Characterization studies were performed for Removal Rate vs. Platen RPM and for Removal Rate vs. Down Force. An increase in removal rate was determined with an increase in platen RPM while a linear relationship between removal rate and down force existed. Blanket nitride and low temperature oxide (LTO) wafers were polished using both silica and ceria slurries to determine removal rates. Oxide to Nitride Selectivity for the Klebosol slurry was 4:1 while the ceria slurry was 100 times more selective. STI structures were manufactured and polished. Trench dishing was studied using Alphastep measurements. Severe dishing was observed with the silica based slurry. The ceria slurry produced no dishing effects.
Selfridge, Robert A.
"CMP Process Development for Shallow Trench Isolation (STI),"
Journal of the Microelectronic Engineering Conference: Vol. 11
, Article 9.
Available at: http://scholarworks.rit.edu/ritamec/vol11/iss1/9