Etching mechanism of (Ba, Sr)TiO3 films in high density Cl2/BCl3/Ar plasma

(Ba, Sr)TiO 3 (BST) thin films have attracted great interest as new dielectric materials of capacitors for ultralarge-scale integrated dynamic random access memories such as 1 or 4 Gbit. In this study, inductively coupled BCl3/ Cl2/Ar plasmas was used to etch BST. The Cl2/(Cl2+Ar) was fixed at 0.2, and the BST thin films were etched by adding BCl3. The characteristics of the plasmas were estimated using optical emission spectroscopy (OES). The change of Cl, B radical density was measured by OES as a function of BCl3 percentage in Cl2/Ar. The cross section of BST thin films and residue remaining after the etch was investigated by scanning electron microscopy. The chemical reactions between BST and Cl2 and the surface of BST films etched with different BCl3/Cl2/Ar gas mixing ratios were investigated using x-ray photoelectron spectroscopy.