Bee. Kastenmeier et al., CHEMICAL DRY-ETCHING OF SILICON-NITRIDE AND SILICON DIOXIDE USING CF4O-2/N-2 GAS-MIXTURES/, Journal of vacuum science & technology. A. Vacuum, surfaces, and films, 14(5), 1996, pp. 2802-2813
Citations number
33
Categorie Soggetti
Physics, Applied","Materials Science, Coatings & Films
The chemical dry etching of silicon nitride (Si3N4) and silicon nitrid
e (SiO2) in a downstream plasma reactor using CF4, O-2, and N-2 has be
en investigated. A comparison of the Si3N4 and SiO2 etch rates with th
at of polycrystalline silicon shows that the etch rates of Si3N4 and S
iO2 are not limited by the amount of fluorine arriving on the surface
only. Adding N-2 in small amounts to a CF4/O-2 microwave discharge inc
reases the Si3N4 etch rate by a factor of 7, but leaves the SiO2 etch
rate unchanged. This enables etch rate ratios of Si3N4 over SiO2 of 10
and greater. The Si3N4 etch rate was investigated with respect to dep
endence of tube length, tube geometry, and lining materials. Argon act
inometry has shown that the production of F atoms in the plasma is not
influenced by the addition of N-2 to the discharge. Mass spectrometry
shows a strong correlation between the Si3N4 etch rate and the NO con
centration. X-ray photoelectron spectra of the silicon nitride samples
obtained immediately after the etching process show that F atoms are
the dominant foreign species in the reaction layer, and that N-2 addit
ion to the feed gas enhances the O atom incorporation. Based on these
data, we propose a mechanism for the etch rate enhancement of N-2 addi
tion to a CF4/O-2 discharge. (C) 1996 American Vacuum Society.