AVS 50th International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS-MoM

Paper PS-MoM5
Loading Effect Study on Cl@sub 2@+HBr Plasma Etching of Polysilicon

Monday, November 3, 2003, 9:40 am, Room 315

Session: Critical Dimension Etching
Presenter: W. Jin, Massachusetts Institute of Technology
Authors: W. Jin, Massachusetts Institute of Technology
H.H. Sawin, Massachusetts Institute of Technology
Correspondent: Click to Email
The effect of etching product buildup, i.e. loading effect, in an inductively coupled plasma etcher for polysilicon etching with Cl@sub 2@+HBr chemistry is studied. In addition to the depletion of reactants, etching products can be fragmented upon collision with energetic electrons into various Si-containing species, with subsequent deposition on the substrate and chamber walls. The role of Si-containing species on the plasma-surface interaction has to be included in the surface kinetic model database for the simulation of etching process. This work uses real plasma beam/QCM to measure the etching yield under different ion bombardment energy and temperatures, and adds SiCl@sub 4@ in Cl@sub 2@/HBr feed gas to mimic the effect of Si-loading observed in a real ICP etcher. The study indicates that the Si-loading can reduce the etching yield significantly, due to the ion-enhanced deposition of Si-containing species on the substrate. The effect of etching yield reduction is more pronounced at lower Si-loading. The plasma beam composition was measured with a mass spectrometer as a function of feed gas composition and Si-loading. The reduction of etching yield at different Si-loading can be explained by the relative concentration of Si, SiCl and SiCl@sub 2@ species at different Si-loading. The surface composition was measured with X-ray photoelectron spectroscopy after etching. The surface composition does not show significant change with Si-loading. A surface kinetics model was developed to relate the etching yield to the beam composition, ion energy and substrate temperature. The insensitivity of surface composition to the Si-loading can also be explained by this model.