AVS 46th International Symposium
    Manufacturing Science and Technology Group Tuesday Sessions
       Session MS-TuA

Paper MS-TuA3
Surface Science of Tungsten CMP Removal

Tuesday, October 26, 1999, 2:40 pm, Room 611

Session: Interconnect and Integration
Presenter: D.J. Stein, Sandia National Laboratories
Authors: D.J. Stein, Sandia National Laboratories
D.L. Hetherington, Sandia National Laboratories
J.L. Cecchi, University of New Mexico
Correspondent: Click to Email
Chemical mechanical polishing (CMP) is the predominant method for planarization and metal damascene processing during manufacture of submicron integrated circuits (IC). Tungsten CMP is used to remove excess tungsten after non-selective chemical vapor deposition in contacts and vias. We have investigated possible mechanisms of tungsten removal under typical IC manufacturing conditions. Previous models for tungsten CMP tungsten suggested that the dominant removal mechanism was the formation of a blanket oxide which was removed by mechanical abrasion.@footnote 1@ We used an electrochemical cell that allowed measurements of the tungsten oxidation rate and the removal rate. We found that the oxidation rate was between 0.01 and 0.1 of the tungsten removal rate, indicating that blanket oxidation does not play a significant role in tungsten removal.@footnote 2@ To elucidate the mechanisms responsible for tungsten removal, we undertook a number of additional investigations, including AFM and TEM imaging, correlations of the polish rate and process temperature dependence with the slurry constituent concentrations, and in-situ measurement of the friction and adhesion between the slurry colloid and the tungsten surface.@footnote 3,4@ We interpret our data with a heuristic model.@footnote 5@ It is shown that the empirical form of the heuristic model fits all of the data obtained. The mechanism also agrees with the limiting cases that were investigated. This mechanism captures the observed relationship between polish rate, pressure, velocity, and slurry chemistry. @FootnoteText@ @footnote 1@F. B. Kaufman et al., J. Electrochem. Soc. 138, 3460, 1991. @footnote 2@D. Stein et al., J. Electrochem. Soc. 145, 3190, 1998. @footnote 3@D. Stein et al., J. Electrochem. Soc. 146, 376, 1999. @footnote 4@D. Stein et al., submitted to J. Mater. Res. @footnote 5@D. Stein et al., accepted for publication in J. Electrochem. Soc.