Porous SiOCH, SiCH and SiO2 etching in high density fluorocarbon plasma with a pulsed bias

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SPECTROSCOPY OF X2Y4(D2h)X_{2}Y_{4} (D_{2h}) MOLECULES: TENSORIAL FORMALISM ADAPTED TO THE O(3)⊃D2hO(3) \supset D_{2h} CHAIN, HAMILTONIAN AND TRANSITION MOMENT OPERATORS. APPLICATION TO THE ν12\nu_{12} and ν2\nu_{2} BANDS OF C2H4C_{2}H_{4}.

$^{a}$W. Raballand, M. Rotger, V. Boudon and M. Lo\""{e}te, J. Mol. Spectrosc., accepted (2003). $^{b}$J.-P. Champion, M. Lo\""{e}te and G. Pierre, in ""Spectroscopy of the Earth's Atmosphere and Interstellar Medium"" (K. N. Rao and A. Weber, Eds.) pp. 339-422, Academic Press, Inc., San Diego (1992). $^{c}$M. Rotger, V. Boudon and M. Lo\""{e}te, J. Mol. Spectrosc., 200, 123-130, (2000). $^{d}$M. Rotger, V. Boudon and M. Lo\""{e}te, J. Mol. Spectrosc., 200, 131-137, (2000). $^{e}$M. Rotger, V. Boudon and M. Lo\""{e}te, J. Mol. Spectrosc., 216, 297-307, (2002). $^{f}$B. G. Sartakov, J. Oomens, J. Reuss and A. Fayt, J. Mol. Spectrosc., 185, 31-47 (1997).Author Institution: Laboratoire de Physique de I'Universit\'{e} de BourgogneA tensorial formalism adapted to the case of $X_{2}Y_{4}$ asymmetric $molecules^{a}$ with $D_{2h}$ symmetry has been developed in the same way as in the previous works on $XY_{4} (T_{b})$ and $XY_{6} (O_{h})$ spherical $tops^{b}, XY_{5}Z (C_{4v})$ symmetric $tops^{c,d}$ or $XY_{2}Z_{2} (C_{2v})$ asymmetric $tops^{e}$. We use the $O(3) \supset D_{2h}$ group chain. The method is similar to that already outlined by Sartakov $et al.^{f}$. All the coupling coefficients and formulas for the computation of matrix elements are given for this chain. Such relations are then expressed in the $D_{2h}$ group itself. We also present a development of the Hamiltonian, dipole moment, and polarizability operators for this type of molecules. Expressions of the matrix elements are derived for these operators. Two preliminary applications are presented. One concerns the infrared active $\nu_{12}$ band of the $C_{2}H_{4}$ molecule and the other the Raman active $\nu_{2}$ band

Etching of low-k materials in high density fluorocarbon plasma

Low dielectric constant materials (low-k) are used as interlevel dielectrics in integrated circuits. This paper concerns the etching process of these materials in high density plasma with the aim to provide some insights concerning the etch mechanisms. Materials studied are methylsilsesquioxane (MSQ) polymers, either dense (SiOC) or containing 40% of porosity (porous SiOC). Amorphous hydrogenated silicon carbide (SiC) material, used as hard mask and/or etch stop layer, is also investigated. Etch is performed in an inductively coupled reactor using fluorocarbon gases, which have proven to be very successful in the etch of conventional SiO2. First, etching with hexafluoroethane (C2F$_{6})$ is performed. Although etch rates are high, etch selectivities with respect to SiC are weak. So, oxygen, argon, and hydrogen are added to C2F6 with the aim of improving selectivities. The best selectivity is obtained for the C2F6/H2 (10%–90%) mixture. To understand etch rate and selectivity variations, plasma analyses by optical emission spectroscopy are correlated to surface analysis using X-Ray Photoelectron Spectroscopy (XPS). In general, atomic fluorine concentration in the plasma explains the etch rate, while the presence of a fluorocarbon layer on the surface is well correlated to the selectivity. To ensure that the etch process does not affect materials properties, and particularly their dielectric constant, bulk analysis by Fourier Transformed Infra-Red spectroscopy and images by Scanning Electron Microscopy have also been carried out

STARK EFFECT IN X2_2Y4_4 MOLECULES: APPLICATION TO ETHYLENE

{W. Raballand, M. Rotger, V. Boudon and M. Loete, {\em J. Mol. Spectrosc.{Ch. Wenger, W. Raballand, M. Rotger and V. Boudon, {\em J. Quant. Spectrosc. Radiat. Transfer{V. Boudon, J.-P. Champion, T. Gabard, M. Loete, F. Michelot, G. Pierre, M. Rotger, Ch. Wenger and M. Rey, {\em J. Mol. Spectrosc.Author Institution: Laboratoire de Physique de l'Uni\-versite de Bourgogne,; UMR CNRS 5027, 9, av. Alain Savary, B.P. 47870, F-21078 Dijon Cedex, France; Max-Planck-Institut fur Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mulheim an der Ruhr, GermanyWe present a development of the dipole moment and polarizability operators of X$_2$Y$_4$ molecules, using a tensorial formalism} {\bf 217}, 239-248, (2003)}$^,$}, accepted, (2005).} analogous to the one developed for tetrahedral and octahedral molecules} {\bf 228}, 620-634, (2004).}. These operators are involved in the calculation of the intensities of rovibrational transitions as well as in the calculation of the Stark effect. Expressions for the matrix elements are derived. A model for the study of the Stark effect in isolated bands of such molecules is proposed and has been used to predict the Stark spectra of the $\nu_{12}$ band of ethylene. Values of the polarizability coefficients have been calculated using {\em ab initio} methods