13 research outputs found
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 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