AVS 46th International Symposium
    Plasma Science and Technology Division Thursday Sessions
       Session PS1-ThA

Paper PS1-ThA5
The Angular Dependence of SiO@sub 2@, Si@sub 3@N@sub 4@, and Poly-Silicon Etching Rates in Inductively Coupled Fluorocarbon Plasmas

Thursday, October 28, 1999, 3:20 pm, Room 612

Session: High Fidelity Pattern Transfer
Presenter: C. Hedlund, Uppsala University, Sweden
Authors: C. Hedlund, Uppsala University, Sweden
F. Engelmark, Uppsala University, Sweden
H.-O. Blom, Uppsala University, Sweden
M. Schaepkens, State University of New York at Albany
G.S. Oehrlein, State University of New York at Albany
Correspondent: Click to Email
Modern plasma etching processes, like self aligned contact (SAC) etching and the damascene and dual damascene dielectric etching, put new demands on the patterning processes. In the fabrication of self-aligned contacts, for instance, the silicon dioxide etching process has to stop on the curved silicon nitride spacer surface. At this curved surface a reduced SiO@sub 2@ to Si@sub 3@N@sub 4@ selectivity commonly is observed. In order to investigate the behavior of the angular dependence of the etch rate and the surface chemistry we prepared structures with a precise angle between the structure surface and the normal of the wafer surface by highly selective wet chemical etching of crystalline silicon. These micro machined structures consisting of either V-grooves or free standing rectangular mesas are ten times smaller than the plasma sheath, resulting in a ion flux normal to the wafer surface. The angular dependence of SiO@sub 2@, Si@sub 3@N@sub 4@, and Poly-Silicon etch rates have been studied in inductively coupled fluorocarbon plasmas. Our data indicate that the reason for the lower selectivity at inclined Si@sub 3@N@sub 4@ and poly-silicon surfaces is the angular dependence of the fluorocarbon film deposition and etching rates. At selective SiO@sub 2@ to Si@sub 3@N@sub 4@ conditions a relatively thin fluorocarbon film is formed on curved surfaces and corners as compared to planar surfaces. The surface chemistry and film thicknesses have been investigated with spectroscopic ellipsometry and. X-ray electron spetroscopy (XPS). The results will be presented along with SEM micrographs of etched structures.