Processing and dielectric property evaluation of barium strontium titanate thin films prepared by a sol-gel technique [DRAM capacitors]

Barium strontium titanate (BST) thin films of the compositions Ba/sub x/Sr/sub 1-x/TiO/sub 3/ with x ranging from 0 to 1 were prepared by a sol-gel spin coating technique. BST solutions were optimized in terms of stability, film crystallization and film quality. Films were deposited on Si (100) and Pt/Ti/SiO/sub 2//Si (100) substrates and the corresponding microstructures were evaluated using techniques such as X-ray diffraction, SEM, FESEM, and TEM. The dielectric breakdown strength was also determined. Grain size was proven to be on the order of 50 nm and had a marked effect on the electrical properties of the films. A dielectric constant ranging from 200 to 625 was obtained for BST thin films with x=0.6 over a thickness range of 100 to 900 nm. The leakage current density of the films remained below 1.1 /spl mu/A/cm/sup 2/ for extended time periods when measured at an applied field of 75 kV/cm.