DIELECTRIC PROPERTIES OF THIN FILM COMPOSITION SPREADS

Abstract

ABSTRACT Dielectrics have been extensively investigated in IC technology for capacitor and transistor applications. The discovery of good amorphous thin-film dielectric materials, with high dielectric constants, low dissipation factors and high breakdown fields for charge storage applications has been of great importance. To identify potential new dielectrics, the composition-spread technique and high throughput experimentation have been widely used to explore materials with excellent properties. In this study, the dielectric properties of amorphous composition-spread thin films were studied. The material systems studied in this work includes Bi-Ti-O, Bi-Ta-O, Bi-Zr-O, Bi-Nb-O and the single composition BaTiO3. Films were deposited by RF magnetron co-sputtering. The Bi-Ti-O composition spread was also annealed via laser spike annealing to explore phase formations, which were further analyzed with synchrotron x-ray diffraction. The dielectric properties of amorphous composition-spread thin films were characterized and discussed. In the composition range of 0.5<x<0.7, amorphous Bi-Ti-O exhibits unexpectedly excellent dielectric properties, with a high dielectric constant, r ~ 53, and a dissipation factor as low as tan  = 0.007. The corresponding maximum breakdown field reaches ~1.6 MV/cm, yielding a maximum stored charge per unit area of up to 8 μC/cm2. This indicates the potential of amorphous Bi-Ti-O as a high-performance thin film dielectric material that is compatible with high-performance integrated circuits. With relatively good frequency-independent dielectric constant, low dissipation factor and good maximum stored charge over a range of compositions, amorphous Bi-Ta-O, Bi-Zr-O and Bi-Nb-O might also be considered candidates for use as capacitor materials. However, these three material systems may not be as good as amorphous Bi-Ti-O. The diffraction analysis of LSA-annealed Bi-Ti-O reveals the formation of the metastable pyrochlore Bi2Ti2O7 and Bi2Ti4O11 phase. In the Bi-rich compositions, δ-Bi2O3 and β-Bi2O3 are stabilized with Ti content, while rutile-type TiO2 is found in Ti-rich compositions. The analysis of dielectric performance of BaTiO3 suggests possible ferroelectric behavior. However, the measurements were not strongly definitive and interpretations proposed are tentative.