Tantalum-chromium alloy films as contact materials for a capacitor using Sr{sub 0.9}Bi{sub 2.1}Ta{sub 2}O{sub 9} for ferroelectric memories

Tantalum-chromium (Ta-Cr) alloy films have been examined as contact materials for ferroelectric memories. Ta-Cr films were prepared by dual-source radio 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 levels of added Cr had high resistivity and a {beta}-Ta structure. Films with intermediate levels of added Cr had high resistivity and an amorphous structure. Films with high levels of pure Cr had low resistivity and a bcc-Cr structure. 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 C in an oxygen atmosphere. The high oxidation resistance of these films has been attributed to the chromic scale surface barrier layer.