The Leakage Current Properties Of BST Multilayered-film Capacitors Prepared By The Sol-gel Method

Barium strontium titanate (BST) film has been investigated extensively for the application in the high density dynamic random access memories (DRAMs). One of the most crucial electrical parameters of these films has been the leakage current level of DRAM cells. Once data has been written in DRAM, charges stored in each capacitor must maintain more than the refresh time so that the information stored in each DRAM cell can be read out correctly. Therefore, leakage current must be kept sufficiently low such that the capacitor does not discharge before it is refreshed.In this paper, multilayered Pt/BST/Pt thin film capacitors were fabricated by the sol-gel process. Both the reverse and forward leakage currents of the Pt/BST/Pt capacitors were reduced several orders of magnitude by employing this multilayered structure with top and bottom layers annealed at low temperatures during the sol-gel deposition of BST films. The observed results could be confirmed by scanning electron microscopy and XRD patterns. And, by varying the concentration of the organic solution of the top amorphous layer, the effective dielectric constants of the capacitors can also be controlled. In addition, we improved the leakage currents and the dielectric properties of BST thin films deposited on Pt/Ti/SiO2/Si substrates with LaNiO3 buffer layers. The similarities in crystal structures and lattice constants between theLaNiO3 and BST films offer the benefits of better lattice matching and structural compatibilities,and the potential for improved dielectric and leakage current properties. The BST films deposited on the LaNiO3/ Pt/ Ti/ SiO2/Si substrates exhibited highly orientation, which can be confirmed by XRD patterns. Low leakage currents, high dielectric constant and low dielectric loss were obtained.