| AVS 54th International Symposium | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS1-ThM |
| Session: | Plasma-Surface Interactions II |
| Presenter: | R.J. Belen, University of California Santa Barbara |
| Authors: | R.J. Belen, University of California Santa Barbara S. Gomez, University of California Santa Barbara M. Kiehlbauch, Lam Research Corporation E.S. Aydil, University of Minnesota |
| Correspondent: | Click to Email |
In sputtering and ion-assisted etching processes, the material removal rate is quantified through the use of the sputtering yield, which depends on the energy and the incidence angle of the ions bombarding the surface. The sputtering or ion-assisted etching yield is defined as the number of surface atoms removed per ion impinging on the surface. The most widely used expression for the sputtering yield assumes that it is a product of separable functions of the ion energy and incidence angle and is proportional to the square root of the ion energy and f(φ), a function that attempts to capture the dependence of the yield on the ion incidence angle, φ, measured with respect to the surface normal. We demonstrate a technique to measure the dependence of the etching yield on the ion incidence angle by examining cross-sectional scanning electron micrographs (SEM) of features etched under realistic plasma conditions in an arbitrary plasma reactor. The idea for the technique described herein is based on the observation that ions bombarding the surface of a semi-circular shaped feature impinge on various points along the feature at different angles that span the range from normal incidence, , φ, = 0°, to grazing incidence, , φ, = 90°. Thus, the technique is based on measuring the etch rate as a function of position along the walls of features that initially have nearly semi-circular cross sections. These initial feature shapes can be easily obtained by wet or isotropic plasma etching of holes patterned through a mask. The etch rate as a function of distance along the feature profile provides the etching yield as a function of the ion incidence angle. The etch rates are measured by comparing digitized SEM cross-sections of the features before and after plasma etching in gas mixtures of interest. We have applied this technique to measure the ion incidence angle dependence of the Si etching yield in HBr, Cl2, SF6 and NF3 plasmas and binary mixtures of SF6 and NF3 with O2. Advantages and limitations of this method will be discussed.