The etching mechanism of (Ba,Sr)TiO3 films using Cl-2/Ar inductively coupled plasma

Abstract

(Ba,Sr)TiO3 thin film is a suitable material for the application in high density dynamic random access memories (DRAMs) because of the high relative dielectric constant and small variation in dielectric properties with frequency. An anisotropic etching of BST thin films is very important in ferroelectric devices to support a small feature size and pattern transfer. In this study, BST thin films were etched with Cl-2/Ar inductively coupled plasma (ICP). The etching characteristic of BST films was studied as a function of Cl-2/(Cl-2+Ar). BST films etched with different Cl-2/Ar gas mixing ratio were investigated using x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometer (SIMS). The surface reaction of the etched (Ba,Sr)TiO3 thin films was investigated with XPS. Pa is removed by chemical reaction such as BaCl2 and physical sputtering. Ar ion bombardment is more effective than chemical reaction between Sr and Cl to remove Sr. Ti is easily removed by chemical reaction such as TiCl4. The result of SIMS analysis compared with the results of XPS analysis were the same.