Interaction of F atoms with SiOCH ultra-low-k films: I. Fluorination and damageстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 9 июня 2015 г.
Аннотация:The interaction of F atoms with porous SiOCH low-k films at a temperature of ~ 14 °C is
studied both experimentally and theoretically. Samples of different ultra-low-k SiOCH films
with a k-value from 1.8 to 2.5 and porosity from 51 to 24% were exposed to F atoms in the
far downstream of an SF6 inductively coupled plasma discharge. The changes occurring
in composition and chemical bonds were studied as a function of exposing F dose using
various techniques such as Fourier transform infrared spectroscopy, x-ray photoelectron
spectroscopy, energy-dispersive x-ray spectroscopy and spectroscopic ellipsometry. It is
shown that fluorination of the pore walls with incorporation of F into surface complexes is
the fastest process of SiOCH modification occurring without an activation barrier. The higher
porosity and the higher pore connectivity promote deeper F penetration and fluorination into
the material. The slower next stage of low-k SiOCH modification is H atom abstraction by
F atoms from –CH3 groups with the formation of –CFxHy surface species. The combined
random walk and kinetics model was developed to analyze the mechanism of the observed
modification. Two mutually dependent parts of the model describe F atom penetration into the
porous film simultaneously with stepwise H replacement in −CH3 groups. The model results
in evolution of chemical modification inside the SiOCH films depending on the F atom dose. It
is shown that the modification depth at F atom impact can be rather large, tens of nanometers
at high porosity, even at low F doses, quite obtainable on etching SiOCH low-k interconnects
in fluorine-based plasmas.