AVS 52nd International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS-MoP

Paper PS-MoP22
Influence of the Positive Ion Composition on the Ion-Assisted Chemical Etch Rate of SrTiO@sub 3@ Thin Films in Ar/SF@sub 6@ Plasmas

Monday, October 31, 2005, 5:00 pm, Room Exhibit Hall C&D

Session: Plasma Science and Technology Poster Session
Presenter: J. Margot, Universite de Montreal, Canada
Authors: O. Langlois, Universite de Montreal, Canada
L. Stafford, Universite de Montreal, Canada
J. Margot, Universite de Montreal, Canada
M. Gaidi, INRS-Energie, Materiaux et Telecommunications, Canada
M. Chaker, INRS-Energie, Materiaux et Telecommunications, Canada
Correspondent: Click to Email
The control of the etch rate is one of the critical issues related to the patterning of functional thin films relevant for applications in electronic, opto-electronic and optical integrated devices. This etch rate is known to be strongly influenced by the reactive neutral and total positive ion density, by the positive ion energy, and by the surface temperature. For plasmas sustained in molecular gases such as BCl@sub 3@, CF@sub 4@, C@sub 4@F@sub 8@, and SF@sub 6@, more than one positive ion species can be present simultaneously in the plasma. It is therefore likely that in addition to the previous parameters, the relative concentration of each positive ion species somewhat impacts the etch rate. In this work, we investigate the influence of the positive ion composition on the ion-assisted chemical etch rate of strontium-titanate-oxide (SrTiO@sub 3@) thin films in Ar/SF@sub 6@ plasmas, using a parametric approach. In this context, we characterize the influence of the operating parameters (e.g. gas pressure and absorbed power) on the positive ion density of each charged species by using plasma sampling mass spectrometry and Langmuir probes. It is found that as either the gas pressure increases or the absorbed power decreases, the relative concentration of molecular positive ion species such as SF@sub 3@@super +@ and SF@sub 5@@super +@ strongly increase. Based on these results, it is possible to define an effective positive ion mass M that describes the overall positive ion composition of the plasma. The SrTiO@sub 3@ etch yield Y (i.e. the number of atoms desorbed from the surface per incident ion) is shown to be a decreasing function of the effective ion mass M, in excellent agreement with the predictions of a simple ion-assisted chemical etching model.