Heteroepitaxial Growth of Ir/ZrN Layered Electrode on (100)Si Substrate for Ferroelectric Capacitor
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85 Mat. Res. Soc. Symp. Proc. Vol. 596 ©2000 Materials Research Society
epitaxally on the (100)ZrN film. In this paper, we show experimental results about the epitaxial growth of the ZrN film on the (100)Si substrate, the Ir film on the ZrN/Si structure and the PZT film on the Ir/ZrN/Si structure. Also, we describe the electrical properties of the epitaxial ZrN, Ir and PZT films and discuss these experimental results briefly. EXPERIMENTAL The deposition conditions for the ZrN, Ir and PZT films are shown in Table I. ZrN films were deposited on n-type (100)Si substrates by RF reactive sputtering with Ar + N 2 gas and a metallic Zr target. The sputtering was carried out after evacuation to a pressure less than 1x 10' Torr using a diffusion pump. The surface oxide layer was removed by a 1% HF solution just before loading the substrate into the deposition chamber. Prior to the deposition, the Zr metallic target was cleaned by sputtering for 15 min with Ar gas to remove the contaminated surface layer of the target. Ir and PZT films were deposited on the ZrN/Si structure by RF sputtering and on the Ir/ZrN/Si structure by RF reactive sputtering with Ar + 02 gas, respectively. In order to keep the Pb content of the film stoichiometric, 16 pieces of 10-mm-diameter PbO pellets were circularly placed on a 4-inch-diameter Pb1 1(Zr 0o 52Ti0.48)O3 disc target. The sample was heated by a PG/PBN heater (Advanced Ceramics) to temperatures of 500 and 750 0C. On the other hand, for 850 and 900'C, it was heated by flowing electric current in the Si substrate, which was attached to the tantalum electrode. The sample temperature was checked by an infrared pyrometer and a thermocouple. The crystallographic properties of the films were investigated by X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED). The depth profile of the chemical composition was analyzed by X-ray photoelectron spectroscopy (XPS). For measurement of the electrical properties of the PZT film, a top electrode of lrO 2 with 0.1-mmdiameter was formed on the PZT film at room temperature by using RF reactive sputtering and a lift-off technique. Prior to deposition of the IRO2, the sample was dipped into 61% HN0 3 solution in order to remove the surface decomposed layer[5,12]. The bottom electrode was the Ir film deposited on the ZrN, where the deposited PZT film on the Ir film was etched with dilute HF solution. After patterning the electrodes, the samples were post-annealed at 300'C in a flowing oxygen atmosphere for 5 min. Polarization-voltage (P-P) measurements were performed using Table Film Target Substrate Temperature Deposition Pressure Sputtering Gas RF Power Density Thickness
I.
Sputtering deposition conditions.
ZrN Zr Metal (4 inch-0) 500-9000C
Ir Ir Metal (4 inch- 0) 500-600°C
0.5 Pa Ar+ N2 (Ar/N 2=9/I) 0.32 W/cm 2 50 nm
4 Pa Ar 0.038 W/cm 2 20 nm
86
PZT Pbl. 1Zr0 .52Ti0.4803 (4 inch- ¢ ) +PbO Pellets(I0 mm- ¢ ) X 16 6000C 0.5 Pa (Ar/0 2=9/1) 0.64 W/cm2 300 nm
Ar+0
2
Sawyer-Tower circuit with a sine wave at 100 Hz. Leakage
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