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 57 nm/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.