Etching of GeSe₂ chalcogenide glass and its pulsed laser deposited thin films in SF₆, SF₆/Ar and SF₆/O₂ plasmas

Excited species, reactive neutral species and positive ions, produced during the etching of Ge, Se and GeSe₂ targets in inductively coupled plasmas, were identified by means of mass spectrometry (MS) and optical emission spectroscopy. The surface of etched Ge₃₉Se₆₁ thin films were analyzed thanks to in situ x-ray photoelectron spectroscopy (XPS) and compared with those of Ge and Se etched samples. In 100% SF₆, the successive adsorption of fluorine atoms forms SeF_x (x = 2, 4, 6) and GeF_x (x = 2, 4) stable and volatile products, generating a surface with few residues as interpreted with in situ XPS. The identification of SSe$F_x^{+}$ (x = 2, 3, 7) ions confirms that sulfur atoms play a role during the etching of Se-containing materials. A 0D kinetic model predicted the evolution of reactive neutral fluxes, ion fluxes and plasma parameters (T _e and n _e) in SF₆/Ar plasmas. It was found that the SeF₆ and GeF₄ concentrations, through Se$F_5^{+}$ and Ge$F_3^{+}$ MS signals, were related to the fluorine atom flux. In SF₆/O₂, the simultaneous effect of fluorine and oxygen adsorption induces (Se)_x–Ge–R _4−x environments (R = F, O) at the surface of the Ge₃₉Se₆₁ thin films. (paper)