Plasma etching dynamics of CaxBa1−xNb2O6 (CBN) material

Abstract

► We study the plasma etching of the Ca x Ba 1− x Nb 2 O 6 in various gases for varying pressures and substrate temperatures. ► Etching at higher pressure increases the redeposition rate and therefore, surface inhibition decreases the etching yield. ► Etching with chlorine is purely physical between −75 and 375 °C in all the conditions. ► Etching with fluorinated gas is inhibited below 150 °C by adsorption of fluor species. ► Desorption of these fluorinated species occurs at higher temperature, removing the surface inhibition. This work reports an extensive study on the etching of Calcium Barium Niobate (CBN, a novel electro-optical material), using high density plasma processes. Different plasma chemistries (inert, chlorine and fluorine plasmas) are used to etch Ca 0.28 Ba 0.76 Nb 2 O 6 (CBN-28) thin films at pressures going from 1 to 10 mTorr, bias voltages going from 0 to 600 V and substrate temperatures ranging from −75 to 375 °C. For all the conditions investigated, the experimental data are compared with a simple sputtering model and completed with TOF-SIMS measurements of some of the samples processed. This study shows that there is no chemical enhancement or inhibition in the case of chlorinated plasma (Cl 2 ) regardless of the ion energy or the substrate temperature. In the case of an SF 6 -Ar plasma, it is shown that the observed increase of the etch yield above 150 °C results from a reduced inhibition as the temperature increases, this inhibition being caused by F and F 2 species adsorption at the surface of the material.