The dielectric properties of (Ba 0.5 Sr 0.5 )TiO 3 films diffused with PbO-Bi 2 O 3 -B 2 O 3 layer
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0902-T10-07.1
The dielectric properties of (Ba0.5Sr0.5)TiO3 films diffused with PbO-Bi2O3-B2O3 layer
Jin Cheol Kim,
Jun Rok Oh
R&D Division, Samsung Electro-Mechanics.
The mixture of PbO-Bi2O3-B2O3 (PBB) were formed on the Ba0.5Sr0.5TiO3 (BST) film and the effects of PBB phase on the dielectric properties of the BST film were investigated. The amorphous PBB layer was deposited on the BST film using rf magnetron sputtering and diffused into the film by heat treatment. The PBB phase in BST film was identified by energy dispersive spectrometer (EDS). Dielectric properties of BST film were significantly improved after the diffusion of PBB. The leakage current density of BST film decreased from 3.24×10-5 A/cm2 to 9.45×10-8 A/cm2 at 1.5 V and the dielectric constant increased from 238 to 533. These results show that the diffusion of insulating metal oxide into the ferroelectric thin film can improve the dielectric properties of the film.
. Introduction High permittivity dielectric films with low leakage current are of great importance for a
variety of integrated devices, such as thin film multi-layer ceramic capacitor(MLCC) and storage capacitors in dynamic random access memory(DRAM).1,2 However, for the application to the real devices, ferroelectric thin films should have low leakage current and high dielectric constant. It was known that these dielectric properities of the ferroelectric thin film are influenced by the microstructure of the film.3 Especially, leakage current significantly increased in the film with columnar grain structure due to the grain boundaries parallel to the thickness of the film.4 To avoid columnar grain structure, BST film was post-annealed after deposition at low temperature, however dielectric constant of this BST film decreased.4 Therefore, the investigation on the new process which can increase both dielectric constant and resistivity of ferroelectric thin film is required. According to the previous works on the grain boundary barrier layer(GBBL) capacitor, metal
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oxide diffused into the ceramics changed the grain boundaries into the insulating layers and thus increased the resistivity and dielectric constant of the ceramics.5 Therefore, if the grain boundaries of the ferroelectric thin film are insulated by the metal oxide, the dielectric properties of the film are expected to be improved. The purpose of this investigation is to increase the resistivity and dielectric constant of the ferroelectric thin film through the formation of the insulating metal oxide layer in the grain boundary of the film. In this work, PBB was diffused into BST film to insulate the grain boundaries of the film and dielectric properties of BST film diffused with PBB were compared with BST film.
. Experimental Procedures BST films of about 50 nm thickness was deposited on the Pt/SiO2/Si substrates at 650 by rf magnetron sputtering and subsequently annealed at 750
for 30 min in N2. The
sputtering was carried out in 55%Ar-45%O2 atmosphere with total pressure of 5 mTorr. After that
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