Dry etching of $(Ba,Sr)TiO3$ thin films using an inductively coupled plasma

In this work, we investigated etching characteristics and mechanism of BST thin films using $Cl2∕Ar,CF4∕Cl2∕Ar$⁠, and $BCl3∕Cl2∕Ar$ gas mixtures using an inductively coupled plasma (ICP) system. A chemically assisted physical etch of BST was experimentally confirmed by ICP under various gas mixtures. The etch rate of the BST thin films had a maximum value at 20% $BCl3$ and 10% $CF4$ gas concentration, and decreased with further addition of $BCl3$ or $CF4$ gas. The maximum etch rate of the BST thin films was $57nm∕min$ at 30% $Cl2∕(Cl2+Ar)$⁠. The maximum etch rate may be explained by the simultaneously concurrence of physical sputtering and chemical reaction. The characteristics of the plasma were analyzed using an optical emission spectroscopy (OES) and a Langmuir probe.