Effects of BCl3 addition in Cl-2/Ar plasma etching of (Ba,Sr)TiO3 thin films

(Ba,Sr)TiO3 (BST) thin films have attracted great interest as new dielectri c materials for capacitors in ultra-large-scale integrated dynamic random a ccess memories, such as 1 or 4 Gbit. In this study, inductively coupled BCl 3/Cl-2/Ar plasma was used to etch BST. The Cl-2/(Cl-2+Ar) ratio was fixed a t 0.2, and the BST thin films were etched by adding BCl3. The characteristi cs of the plasmas were estimated using optical emission spectroscopy. Optic al emission spectroscopy was used to measure the changes in the Cl and the B radical densities as functions of BCl3 percentage in the Cl-2/Ar mixture. The cross sections of the BST thin films and the residue remaining after e tching process were investigated by using scanning electron microscopy. The chemical reactions between BST and Cl-2 on the surface of BST films etched with different BCl3/Cl-2/Ar gas mixing ratios were investigated using X-ra y photoelectron spectroscopy.