AVS 52nd International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS-ThM

Paper PS-ThM10
Investigation of the Etching Characteristics of SrTiO@sub 3@ Films in Halogenated High-Density Plasmas

Thursday, November 3, 2005, 11:20 am, Room 304

Session: Plasma-Surface Interactions II
Presenter: L. Stafford, Universite de Montreal, Canada
Authors: L. Stafford, Universite de Montreal, Canada
O. Langlois, Universite de Montreal, Canada
M. Gaidi, INRS-Energie, Materiaux et Telecommunications, Canada
J. Margot, Universite de Montreal, Canada
M. Chaker, INRS-Energie, Materiaux et Telecommunications, Canada
J. Saussac, Universite de Montreal, Canada
Correspondent: Click to Email
SrTiO@sub 3@ (STO) films have recently received much attention because of their potential applications into waveguides for optical integrated systems. Up till now, relevant issues related to the development of an efficient patterning process for STO remain however to be solved. This is vital since the performances of the device critically depend upon the STO etching characteristics, particularly upon the roughness of the etched profiles. In this context, we investigate in this work the etching characteristics of STO films using a low-pressure high-density plasma operated in halogenated gas mixtures. We found that the addition of Cl@sub 2@ and SF@sub 6@ to the Ar plasma significantly reduces the etch rate. A correlation between the etch rate data and the plasma characteristics obtained from Langmuir probes and actinometry, indicates that this decrease results in part from the lower positive ion density in Ar/Cl@sub 2@ and Ar/SF@sub 6@ plasmas. Using a recently developed surface reaction model for ion-assisted chemical etching,@footnote 1@ we demonstrate that in both Ar/Cl@sub 2@ and Ar/SF@sub 6@ plasmas, (i) the etch rate is ion-flux limited (i.e. independent of the reactive neutral density) and that (ii) chlorine and fluorine reactive neutral species act as inhibitors in the etching process of STO. A characterization of the post-etched surface by X-Ray Photoelectron Spectroscopy (XRPS) and Secondary Ion Mass Spectrometry (SIMS) measurements indicates that inhibition results from the formation of a thin SrCl@sub x@ or SrF@sub x@ layer, which impedes the formation and/or the desorption of TiCl@sub x@ or TiF@sub x@ volatile products. Finally, based on XRPS and SIMS measurements, we propose a two-layer model for the representation of the surface in the course of etching. @FootnoteText@ @footnote 1@ L. Stafford, J. Margot, M. Chaker, & S.J. Pearton, "Energy dependence of ion-assisted chemical etch rates in reactive plasmas", submitted to Appl. Phys. Lett. 21/12/2004.