AVS 49th International Symposium
    Plasma Science Monday Sessions
       Session PS1-MoA

Paper PS1-MoA8
Ferroelectric Etching Characteristics in Ar/Cl@sub 2@ and in Ar/SF@sub 6@ Mixtures

Monday, November 4, 2002, 4:20 pm, Room C-103

Session: Dielectric Etch I
Presenter: L. Stafford, Universite de Montreal, Canada
Authors: L. Stafford, Universite de Montreal, Canada
J. Margot, Universite de Montreal, Canada
M. Chaker, INRS-Energie et Materiaux, Canada
Correspondent: Click to Email
Ferroelectric materials such as barium-strontium-titanate (BST) and strontium-bismuth-tantalate (SBT) are promising for many applications, including high-k DRAMs, FeRAMs and microwave components in the millimeter wavelength range. In order to integrate these materials to various devices, the development of reliable and efficient patterning processes is a crucial issue. In this context, it was recently shown that excellent etching characteristics for BST and SBT could be achieved using a pure argon high-density plasma, provided it is operated in the very low-pressure regime (i.e. 1 mTorr or less).@footnote 1@ However, scientific literature indicates that the use of reactive fluorinated or chlorinated plasmas may still improve the process. For this reason, we have investigated the etching of BST using Cl@sub 2@-Ar mixtures. The emphasis is put on the influence of the experimental conditions (total gas pressure and Cl@sub 2@ percentage in Ar) on the etch rate and on the selectivity over HPR-504 photoresist. The etching results are correlated to the plasma characteristics, including positive ion density, ion energy and reactive neutral atom concentration as obtained from various plasma diagnostics (Langmuir probes, mass spectrometry on ions and neutrals, and actinometry). Our results show that the etch rate is directly proportional to the positive ion density, whatever the experimental conditions yielding that density. This indicates that in the range of pressures investigated, the etching mechanism is dominated by sputtering. Thus, considering the fact that for given experimental conditions, the ion density in chlorine is significantly lower than in argon, the use of argon thus appears more advantageous than Cl@sub 2@ to achieve high etch rates together with a good selectivity. These results will also be compared to those obtained in Ar/SF@sub 6@. @FootnoteText@ @footnote 1@ L. Stafford et al., J. Vac. Sci. Technol. A, 20(2), pp. 530-535 (2002).