Chemical and microstructural characterization of rf-sputtered BaTiO_3 nano-capacitors with Ni electrodes

摘要

Chemical and microstructural evaluation techniques have been used to characterize sputter deposited 100-150 nm thick BaTiO_3 nano-capacitors with 30 nm thick Ni electrodes fabricated on Si/SiO_2 wafers. More than 99% of devices had resistance > 20 MΩ. Electrodes were found to have a roughness, R_a, of about 0.66 ± 0.04 nm, and the BaTiO_3 had a R_a value of 1.3 ± 0.12 nm. Characterization of the BaTiO_3 film chemistry with X-ray Photoelectron Spectroscopy (XPS) showed the films had excess oxygen and Ba:Ti ratios ranging from 0.78 to 1.1, depending on sputtering conditions. X-ray diffraction showed a broad peak between approximately 20° and 35° 2θ, indicating the films were either amorphous or contained grain sizes less than 5 nm. Focused ion beam images confirmed the presence of smooth, conformal films, with no visible signs of macro-defects such as pin-holes, cracks, or pores. High resolution transmission electron microscopy (TEM) and electron diffraction patterns confirmed the presence of a nearly amorphous film with limited short range order. No correlation was found between the chemical and microstructural studies with the dielectric permittivity (280-1000), loss (0.02-0.09), and/or resistivity (8.7 × 10~(10)-1.5 × 10~(12) Ωcm) values.