Electro-Ceramics Lab. Electrical Properties of SrBi 2 Ta 2 O 9 Thin Films Prepared by r.f. magnetron sputtering Electro-ceramics laboratory Department of Materials Engineering, Sangju National University, , Sangu, kyungbuk, Korea

Electro-Ceramics Lab. OUTLINE ▶ Introduction Why SrBi 2 Ta 2 O 9 thin Films ? ▶ Preparation of SBT thin films by PEMOCVD ▶ Formation of oxide interfacial phase at interface between SBT and Pt ▶ Electric Properties of SBT thin films ▶ Summary

Electro-Ceramics Lab. Ferroelectric thin Films(Especially, PZT) Degradation problems Fatigue Imprint Aging Solution for fatigue Conductive oxide electrode(LSCO, RuO 2, IrO 2 ) Doping(La, Nb) Ferroelectric SrBi 2 Ta 2 O 9 thin Films Bi-layer structure Low intrinsic defect Good ferroelectric switching characteristics Attractive materials for the nonvolatile memory devices Why SrBi 2 Ta 2 O 9 thin Films ? Introduction

Electro-Ceramics Lab. Experimental Conditions Deposition temperature RF power Distance between electrodes System pressure Bubbling temperature of Sr(hfa) 2 (tet) Ar gas flow rate of Sr source Bubbling temperature of Bi(C 6 H 5 ) 3 Ar gas flow rate of Bi source Bubbling temperature of Ta(C 2 H 5 O) 5 Ar gas flow rate of Ta source O 2 gas flow rate Deposition time Substrate o C 130 W 3 cm 2 torr 120 o C 80 sccm 150 o C 80 sccm 130 o C 15 sccm 200 sccm 80 min. MOCVD-Pt/SiO 2 /Si Pt/Ti/SiO 2 /Si SBT by PEMOCVD Deposition parameters

Electro-Ceramics Lab. XRD Analysis X-ray diffraction patterns of the SrBi 2 Ta 2 O 9 films deposited on (a) MOCVD-Pt/SiO 2 /Si and (b) Pt/Ti/SiO 2 /Si

Electro-Ceramics Lab. XRD Analysis X-ray diffraction patterns of the Bismuth films annealed at 800 ℃ in oxygen ambient after deposition on Pt/Ti/SiO 2 /Si at room temperature.

Electro-Ceramics Lab. TEM Analysis Cross-sectional TEM images of SBT films deposited on (a) Pt/SiO 2 /Si (b) Pt/Ti/SiO 2 /Si (a)(b) BTO Pt/Ti SiO 2

Electro-Ceramics Lab. #1 #2 #4 #5 500nm (A)(C) TiO Pt (B) AES Analysis (A),(B) SEM image and (C) AES spectra of Pt/Ti/SiO 2 /Si substrates before deposition of SBT thin films #3

Electro-Ceramics Lab. (a) SIMS depth profile and (b) RBS of the SBT films deposited on Pt/Ti/SiO 2 /Si SIMS and RBS Analysis Ta Sr Pt Ti Bi O Si (a) Sputt. Time (Sec) Counts / Sec Si Ti Ta Bi Pt Sr The composition of SBT/Pt interface(35nm thickness) O Ta-7.00 Bi-7.00 Pt Si Ti-8.00 Sr 0.8 Bi 2.0 Ta 2.0 O TheoreticalExperiment (b)

Electro-Ceramics Lab. RBS Analysis The Composition of SBT films deposited on Pt/Ti/SiO 2 /Si Channels Experimental Theoretical Si Ti Ta Bi Pt Sr The composition of SBT/Pt interface(35nm thickness) O Ta-7.00 Bi-7.00 Pt Si Ti-8.00 Sr 0.8 Bi 2.0 Ta 2.0 O 9

Electro-Ceramics Lab.   r and tan  vs. Temperature Temperature dependence on the dielectric constant and dissipation factor of SBT/Pt/Ti/SiO 2 /Si films at various frequencies

Electro-Ceramics Lab. Leakage Current Density (a) Current-time curve under dc field of 2 V and (b) I-V curve of SBT films with delay time of 1 sec

Electro-Ceramics Lab. Schottky Barrier height (a) The leakage current density (J) vs. applied voltage of SBT films deposited on Pt/Ti/SiO 2 /Si as a function of temperature and (b)log (J/T 2 ) vs. 1/T at the various applied voltages. ln [Δ(J/T 2 ) = q  B /k[Δ(1/T)] Schottky barrier height :  B = ~ 1.2 eV

Electro-Ceramics Lab. Schottky Barrier height (a) The leakage current density (J) vs. applied voltage of SBT films deposited on Pt/SiO 2 /Si as a function of temperature and (b) log ( J/T 2 ) vs. 1/T at the various applied voltages. ln [Δ(J/T 2 ) = q  B /k[Δ(1/T)] Schottky barrier height :  B = ~ 0.8 eV

Electro-Ceramics Lab. P-E Curves Hysteresis loops of SBT films prepared on (a) MOCVD-Pt/SiO 2 /Si and (b) Pt/Ti/SiO 2 /Si substrates

Electro-Ceramics Lab. Fatigue Characteristics Fatigue Characteristics of SBT films deposited on (a) MOCVD-Pt/SiO 2 /Si (b) Pt/Ti/SiO 2 /Si (a)(b)

Electro-Ceramics Lab. Summary ▶ SrBi 2 Ta 2 O 9 thin films were successfully prepared at 550 ℃ by Plasma -enhanced MOCVD. ▶ BTO(Bi 4 Ti 3 O 12 ) phase were formed at interface between SBT and Pt/Ti/SiO 2 /Si. ▶ BTO phase decreased the leakage current density of SBT thin films. ▶ Schottky barrier height of Pt/SBT/Pt capacitor  B = ~ 0.8 eV without Ti layer  B = ~ 1.2 eV with Ti buffer layer ▶ SBT thin films showed fatigue free characteristics up ~10 11 switching cycles