Deposition and characterization of ZrO 2 thin films on silicon substrate by MOCVD
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ZrO 2 thin films were deposited at 1 atm on Si substrates by oxidation-assisted thermal decomposition of zirconium-trifluoroacetylacetonate in the temperature range of 300-615 °C. Above a deposition temperature of 400 °C, the deposited thin films have a columnar grain structure, where each grain is perpendicular to the substrate surface with a c-axis preferred crystallographic orientation, and have poor electrical characteristics as a dielectric thin film. But the thin film deposited at 350 °C has a fine equiaxed microcrystalline structure and has superior electrical characteristics of a breakdown field of 1 MV/cm and a relative dielectric constant of 27.
I. INTRODUCTION The study of deposition of various metal oxide thin films such as TiO 2 , 12 Ta2O5,3'4 ZrO 2 , 5 ' 6 Y 2 O 3 , 7 A12O3,8 and high-temperature superconducting materials9'10 on Si single crystal and other substrates by CVD is actively being pursued. In particular, the use of metal-organic materials as starting precursor materials makes it possible to deposit the various oxide thin films at a relatively low temperature by CVD. Therefore, the application of high dielectric constant thin films such as TiO2, ZrO 2 , and Ta 2 O 5 deposited by MOCVD to microelectronics will introduce ultrahigh density integrated circuit and new-type electronic devices. ZrO 2 is an insulating material with a large relative dielectric constant of about 18, a wide band gap of 5.1 eV, and excellent chemical inertness.5 ZrO 2 thin film has potential use as a storage capacitor in the DRAM cell. ZrO 2 is also an interesting material as an insulating layer in silicon-on-insulator (SOI) devices because pure or stabilized ZrO 2 can be closely matched in lattice constant to silicon. Deposition of ZrO 2 thin films was first attempted by Tauber et al.5 using high-temperature hallide CVD. Balog et al.6 deposited ZrO 2 thin film on Si and other substrates using zirconium-trifluoroacetylacetonate (Zr-TFA) and O 2 as source materials at a low temperature (300-900 °C), and showed the possibility of ZrO 2 thin film being used as a dielectric material for microelectronics. Recently Liau and Weppner11 proposed the usefulness of stabilized zirconia thin film as an oxygen sensor. The deposition methods of ZrO 2 thin films include high-temperature chloride CVD,5 low-temperature MOCVD, 6 reactive ion-beam sputtering from metal and oxide targets,12 reactive r.f. sputtering from a metal target,13'14 and electron beam evaporation.15 The MOCVD using /3— diketonate precursor is one of the J. Mater. Res., Vol. 8, No. 6, Jun 1993 http://journals.cambridge.org
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most suitable processes for the deposition of ZrO 2 thin films for microelectronics because the chloride CVD requires a high substrate temperature. The electron beam evaporation can produce epitaxial ZrO 2 thin films on Si, but in this method a high substrate temperature (800-1000 °C) is required. The r.f. diode sputtering from a metal target under oxidation atmosphere can produce good quality ZrO 2 thin films on quartz su
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