• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.377-380
• /
• 2001

The BST thin films to composite (Ba$\sub$x/Sr$\sub$l-x/)TiO$_3$ using sol-gel method were fabricated on Pt/Ti/SiO$_2$/Si substrate. The thin film capacitor to be ferroelectric materials was investigated by structural and electrical properties. BST solution was composited by moi ratio, and then spin-coated (from 3 times to 5 times coating on Pt/SiO$_2$/Si substrate. Thickness of BST ceramics thin films are about 2600∼2800[${\AA}$] in 3 times deposition. The property of leakage current was stable when the applied voltage was 3[V]. Leakage current of 3 times coated BST thin film was 10$\^$-9/∼10$\^$-11/[A] at 0∼3[V].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.03a
• /
• pp.21-21
• /
• 2010

(Ba,Sr)$TiO_3$ (BST) thin film with a perovskite structure has potential for the practical application in various functional devices such as nonvolatile-memory components, capacitor, gate insulator of thin-film transistors, and electro-optic devices for display. Normally, the BST thin films derived from sol-gel and sputtering are amorphous or partially crystalline when processed below $600^{\circ}C$. For the purpose of integrating BST thin film directly into a Si-based read-out integrated circuit (ROIC), it is necessary to process the BST film below $400^{\circ}C$. The microstructural and electrical properties of low-temperature crystallized BST film were studied. The BST thin films have been fabricated at $350^{\circ}C$ by UV-assisted rapidly thermal annealing (RTA). The BST films are in a single perovskite phase and have well-defined electrical properties such as high dielectric constant, low dielectric loss, low leakage current density, and high breakdown voltage. Photoexcitation of the organics contained in the sol-gel-derived films by high-intensity UV irradiation facilitates elimination of the organics and formation of the single-crystalline phase films at low temperatures. The amorphous BST thin film was transformed to a highly (h00)-oriented perovskite structure by high oxygen pressure processing (HOPP) at as low as $350^{\circ}C$. The dielectric properties of BST film were comparable to (or even better than) those of the conventionally processed BST films prepared by sputtering or post-annealing at temperature above $600^{\circ}C$. When external pressure was applied to the well-known contractive BST system during annealing, the nucleation energy barrier was reduced; correspondingly, the crystallization temperature decreased. The UV-assisted RTA and HOPP, as compatible with existing MOS technology, let the BST films be integrated into radio-frequency circuit and mixed-signal integrated circuit below the critical temperature of $400^{\circ}C$.

• Proceedings of the KIEE Conference
• /
• 1997.07d
• /
• pp.1491-1493
• /
• 1997

In this study, Sol-Gel derived $Ba_{0.7}Sr_{0.3}TiO_3$ (BST(70/30)) thin films were investigated. The stock solution of BST were fabricated and spin-coated on the Pt/Ti/$SiO_2$/Si and ITO/glass substrates. The coated specimen were dried at $300^{\circ}C$ and finally annealed at $650{\sim}750^{\circ}C$. To analyse crystallization condition and microstructural morphology for different substrates, XRD, and SEM analysis were processed. In the BST(70/30) composition. dielectric constant and loss characteristics measured at 1kHz were 173, 0.01% for Pt/Ti/$SiO_2$/Si substrates and 181, 0.019% for ITO/glass substrates, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.263-266
• /
• 2001

In this paper, we investigated dielectric properies for BST thin films that was deposited on MgO/Si substrates using RF magnetron sputtering. In here, MgO film was used to perform that a diffusion b arrier between the BST film and Si substrate and a buffer layer to assist the BST film growth. A d eposition condition for MgO films was RF Power of 50W, substrate temperature of room temperature and the working gas ratio of Ar:O$_2$ were varied from 90:10 to 60:47. Finally we manufactured the cap acitor of Al/BST/MgO/Si/Al structure to know electrical properties of this capacitor through I-V, C-V measurement. In the results, C-V aha racteristic curves was shown a ferroelectric property so we measured P-E. A remanent poliazation and coerceive electric field was present 2$\mu$C/cm$^2$ and -27kV/cm respectively at Ar:O$_2$=90:10. And a va clue of dielectric constant was 86 at Ar:02=90:10.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.6
• /
• pp.504-510
• /
• 2002

Recently, thin film capacitors of high dielectric constant and low leakage current are applied to integrated devices. In this study, (Ba, Sr)$TiO_3$ (BST) thin films for low cost were prepared by Sol-Gel method. BST solution was spin-coated on Pt/$SiO_2$/Si substrate at 4,000 rpm for 10 seconds. Coating process was repeated 3 times and then sintered at $700^{\circ}C$ for 30 minutes. Structural and electrical characteristics of each specimen were analyzed by TG-DTA, SEM, fractal phenomenon, voltage-current and dielectric factor. Thickness of BST ceramics thin films are about 2,600~2,800 ${\AA}$ at depositing 3 times. Dielectric constant of thin films was decreased in 1 kHz~1 MHz. Dielectric constant and loss to frequency were 250 and 0.02 in $(Ba_{0.7}Sr_{0.3})TiO_3$ (BST3). Leakage current of BST3 was $10^{-9}\sim10^{-11}$/ A under 3 V.

• Proceedings of the KIEE Conference
• /
• 1999.11a
• /
• pp.31-34
• /
• 1999

In the present study, we fabricated stoichiometric $(Ba_{1-x}Sr_x)TiO_3$ thin films at various substrate temperature and contents using of magnetron sputtering method on optimized Pt-based electrodes (Pt/TiN/$SiO_2$/Si). The substate temperature deposited at 200[ $^{\circ}C$], 400[$^{\circ}C$] and 600[$^{\circ}C$] and crystalline BST thin films show above 400[$^{\circ}C$]. Also, the composition of $(Ba_{1-x}Sr_x)TiO_3$ thin films deposited on Si wafer substrate at 400[$^{\circ}C$] were closed to stoichiometry($1.015{\sim}1.093$ in A/B ratio), but compositional deviation from a stoichiometry is larger as $SrCO_3$ is added. The drastic decrease of dielectric constant and increase of dielectric loss in $(Ba_{1-x}Sr_x)TiO_3$thin films is observed above 100[kHz]. V-I characteristics of $(Ba_{1-x}Sr_x)TiO_3$ thin films show the decrease of leakage current with the increase of $SrCO_3$ contents.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.14 no.3
• /
• pp.90-94
• /
• 2004

The variation of electrical properties of (Ba,Sr)$TiO_3$ [BST] thin films for Metal-Insulator-Semiconductor (MIS) capacitors was investigated. BST thin films were deposited on p-Si(100) substrates by the RF magnetron sputtering with temperature range of 500~$600^{\circ}C$. The dielectric properties of MIS capacitors consisting of AUBST/$SiO_2$/Si sandwich structure were measured for various conditions. We examined the characteristics of MIS capacitor with various oxygen pressure, substrate temperature and (Ba+Sr)/Ti ratio. It was found that the leakage current was reduced in MIS capacitor with high quality $SiO_2$ layer was grown on bare p-Si substrate by thermal oxidation. The BST MIS structure showed relatively high capacitance even though it is the combination of high-dielectric BST thin films and $SiO_2$ layer. The charge state densities of the MIS capacitors and Current-voltage characteristics of the MIS capacitor were investigated. By applying $SiO_2$ layer between BST thin films and Si substrate, low leakage current of $10^{-10}$ order was observed.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2002.11a
• /
• pp.370-374
• /
• 2002

This paper describes the design and fabrication of distributed analog phase shifter circuit. The phase shifter consist of coplanar waveguide(CPW) lines that are periodically loaded with voltage tunable (Ba,Sr)TiO$_3$ thin film interdigital(IDT) capacitors deposited by the pulsed laser deposition(PLD) on (001) MgO single crystals. The phase velocity on these IDT loaded CPW lines is a function of applied bias voltage, thus resulting in analog phase shifting circuits. The measured differential phase shift is 48$^{\circ}$ and the insertion loss decreases from -5㏈ to -3㏈ with increasing bias voltage from 0 to 40 V at 100㎐.

• Proceedings of the KIEE Conference
• /
• 1998.11c
• /
• pp.798-800
• /
• 1998

(Ba,Sr)$TiO_3$ thin films were etched with $Cl_2$/Ar gas mixing ratio in an inductively coupled plasma (ICP) by varying the etching parameter such as f power, do bias voltage, and chamber pressure. The etch rate was $560{\AA}/min$ under Cl_2/(Cl_2+Ar)$ gas mixing ratio of 0.2, rf power of 600 W, do bias voltage of 250 V, and chamber pressure of 5 mTorr, At this time, the selectivity of BST to Pt, $SiO_2$ was respectively 0.52, 0.43. The surface reaction of the etched (Ba,Sr)$TiO_3$ thin films was investigated with X-ray photoelectron spectroscopy (XPS).

• Journal of the Korean Ceramic Society
• /
• v.34 no.8
• /
• pp.803-810
• /
• 1997

Ba0.5Sr0.5TiO3 thin films were deposited by RF magnetron sputliring method in order to clarify the anneal condition and doping effect on loakage current Nb and Al were selected as electron donor and acceptor dopants respectively, in the BST films because they have been known to have nearly same ionic radii as Ti and thought to substitute Ti sites to influence the charge carrier and the acceptor state adjacent to the gram boundary. BST thin films prepared in-situ at elevated temperature showed selatively high leakage current density and low breakdown voltage. In order to achieve smooth surface and to improve electrical properties, BST thin films were deposited at room temperature and annealed at elevated temperature. Post-annealed BST thin films showed smoother surface morphology and lower leakage current density than in-situ prepared thin films. The leakage current density of Al doped thin films was measured to be around 10-8A/cm2, which is much lower than those of undoped and Nb doped BST films. The result clearly demonstrates that higher Schottky barrier and lower mobile charge carrier concentration achieved by annealing in the oxygen atmosphere and by Al doping are desirable for reducing leakage current density in BST thin films.