Tantalum-chromium alloy films as contact materials for a capacitor using Sr0.9Bi2.1Ta2O9 for ferroelectric memories

Tantalum-chromium (Ta-Cr) alloy films have been examined as contact materia ls for ferroelectric memories. Ta-Cr films were prepared by dual-sourer rad io frequency (rf)-magnetron sputtering and with a film composition that was varied by control of rf power applied to the targets. Three types of films were obtained by the controlling film composition. Films with no or low le vels of added Cr had high resistivity and a beta-Ta structure. Films with i ntermediate levels of added Cr had high resistivity and an amorphous struct ure. Films with high levels of pure Cr had low resistivity and a bcc-Cr str ucture. Amorphous Ta-69%Cr and crystalline Ta-74%Cr alloy films were highly stable despite changes in thermal and oxidation conditions, maintaining a constant resistivity even after annealing at 700 degrees C in an oxygen atm osphere. The high oxidation resistance of these films has been attributed t o the chromic scale surface barrier layer. (C) 2000 The Electrochemical Soc iety. S0013-4651(99)08-069-6. All rights reserved.