AVS 47th International Symposium
    Surface Engineering Tuesday Sessions
       Session SE-TuA

Paper SE-TuA7
Cleaning, Etching and Oxidation of W films for Microelectronics Applications

Tuesday, October 3, 2000, 4:00 pm, Room 201

Session: Surface Engineering: Surface Preparation to Postcoating Surface Finishing
Presenter: E.J. Mitchell, Southwest Texas State University
Authors: P. Cao, University of Houston
M.-S. Lim, University of Houston
S.S. Perry, University of Houston
E.J. Mitchell, Southwest Texas State University
D.C. Koeck, Southwest Texas State University
H.C. Galloway, Southwest Texas State University
Correspondent: Click to Email
During the fabrication of integrated circuits with tungsten plugs, the tungsten surface undergoes chemical mechanical planarization (CMP). It is important to characterize the effects of any pre- or post-processing cleaning steps on the tungsten surface. To investigate this, we have examined tungsten films prepared by chemical vapor deposition (CVD) to carefully characterize how they respond to common cleaning and etching procedures. Topography changes were examined by atomic force microscopy and surface chemistry was characterized by X-ray photoelectron spectroscopy (XPS). Cleaning and etching procedures investigated in this study include solutions of KNO@sub 3@ and H@sub 2@O@sub 2@, KOH, a buffered solution of KIO@sub 3@ and NaOH as well as the RCA SC-1 clean. The relative ability of these cleaning treatments to remove residual hydrocarbons from the W surface has been evaluated. In addition, the influence of these treatments on the native tungsten oxide layer has been measured as well. The XPS results show a general increase in the oxidation state in W for most solutions, specifically entailing an increase in W@super 6+@ and a corresponding decrease in W@super 4+@. These results are relevant to both material removal during the CMP process and the effectiveness of cleaning procedures. A correlation of the results shows that weakly oxidizing solutions are not as effective in removing organic contaminants as strongly oxidizing solutions.