Chemical Dry Etching of Silicon by Discharge Flow of Ar/CF4 Gas Mixtures : Identification of Ar Active Species Responsible for the Formation of Etchant

Chemical dry etching of Si by Ar/CF$_4$ gas mixtures has been studied using a discharge-flow apparatus. Active species of Ar generated by a microwave discharge of Ar/CF$_4$ mixtures are ${\rm Ar}({}^3{\rm P}_{0,2})$, ${\rm Ar}^+({}^2{\rm P}_{1/2,3/2})$, and metastable ${\rm Ar}^{+*}$ ions. The responsible Ar active species for the formation of F atoms were examined by measuring the dependence of their relative concentrations on the Ar flow rate. The dependence of etch rate on the Ar flow rate was similar to that of ${\rm Ar}({}^3{\rm P}_{0,2}$. It was therefore concluded that the metastable ${\rm Ar}({}^3{\rm P}_{0,2}$ atoms are most significant active species for the generation of F atoms