Study on surface reaction of (Ba,Sr)TiO3 thin films by high density plasmaetching

Ferroelectric devices are extremely useful for dynamic random access memori es applications because of their high dielectric constant. Using ferroelect ric device structure, manufacturing cell capacitance df highly integrated m emory device is possible. The small feature size requires anisotropic etchi ng. Since the research of (Ba, Sr)TiO3 thin film etching is:seriously lacki ng, we Studied the surface reaction of (Ba, Sr)TiO3 thin films by using hig h. density plasma etching. In this study, (Ba, Sr)TiO3 thin films were etch ed with Cl-2/Ar gas combination in an inductively coupled plasma. This was done by varying the etching parameters. Such as radio frequency power, dire ct current bias, and chamber pressure. The maximum etch rate of the BST fil ms was 560 Angstrom/min under Cl-2/(Cl-2+Ar) of 0.2, 600 W/250 V, and 5 mTo rr. The selectivity of BST to Pt and SiO2 was 0.52, 0.43, respectively. The surface reaction of the etched (Ba, Sr)TiO3 thin films was investigated wi th x-ray photoelectron spectroscopy (XPS) using narrow scan spectra. Ba 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 r emove Sr. Ti is removed by chemical reaction such as TiCl4 with ease. The r esults of secondary ion mass spectrometer analysis;were compared with the r esults of XPS analysis and the results were the same. (C) 1999 American Vac uum Society. [S0734-2101(99)19804-X].