AVS 45th International Symposium
    Plasma Science and Technology Division Wednesday Sessions
       Session PS-WeA

Paper PS-WeA4
The Ion-assisted Etching and Profile Development of Silicon in Molecular and Atomic Chlorine: Experiment, Modeling, and Simulation

Wednesday, November 4, 1998, 3:00 pm, Room 318/319/320

Session: Plasma-Surface Interactions I
Presenter: J.A. Levinson, Stanford University
Authors: J.A. Levinson, Stanford University
E.S.G. Shaqfeh, Stanford University
M. Balooch, Lawrence Livermore National Laboratory
A.V. Hamza, Lawrence Livermore National Laboratory
Correspondent: Click to Email
We report on an ion beam etching study designed to characterize the important kinetic and transport processes involved in the ion-assisted etching of silicon in both molecular and atomic chlorine. Monoenergetic argon ions were directed normal to a silicon wafer that was simultaneously exposed to a neutral molecular and/or atomic chlorine beam. Dissociation of the beam was induced by thermally heating the graphite tip of the effusive source via electron impact. Beam composition was characterized using a quadrupole mass spectrometer. Unpatterned polysilicon wafers were etched to determine the ion-induced etching yields as a function of ion energy, ion to neutral flux ratio, and neutral flux composition. A physically-based kinetic model was developed to represent the yield data. Feature etching experiments using patterned silicon wafers were also performed under ion-limited and neutral-limited conditions of varying neutral composition. Resulting profiles were examined for aspect-ratio dependent etching lag as caused by neutral starvation and/or atomic to molecular chlorine recombination. Computer simulations of the etching process and profile development were performed using the kinetic model and a line-of-sight re-emission model for the chlorine transport. The dependence of the yield on the ion angle of incidence was also incorporated into the simulation and was found to have a significant impact on profile evolution as a function of the ion to neutral flux ratio. Atomic to molecular chlorine recombination effects were explored as a function of the surface recombination coefficient. Predictions of the simulations were compared to experimentally-derived profiles.