Selective SiN/SiO2 etching by SF6/H2/Ar/He plasma

Abstract

This paper presents the experimental data about SiN and SiO2 etching by SF6/H2/Ar/He plasma discharge. It has been shown that SiN etch rate increases if add small amount of He (less than 5 sccm) into the discharge. The SiO2 etch rate does not depend on He content in the plasma discharge and is almost the constant. The possible role of helium appears in reactions with H2 species. Namely, He or metastable He∗ increases rate of H-atoms production. It is known from the previous publications that H-atoms enhance SiN etching. Thus, helium can help to selectively etch silicon nitride over silicon oxide.