• Journal of the Korean Vacuum Society
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• v.4 no.S1
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• pp.138-144
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• 1995

It is commonly believed that high permittivity materials will be necessary for future high density Gbit DRAMs. In a first part, we explain the choice of SrTiO3 by ECR MOCVD for Gbit-scale DRAMs. In a second part, after describing the ECR MOCVD system and presenting the requirements SrTiO3 thin films should meet for use in Gbit-scale DRAMs, the physical and electrical properties of srTiO3 thi film prepared by ECR MOCVD are then studied. A stacked capacitor technology, suitable for use in 1 Gbit DRAM, and comprising high permittivity SrTiO3 thin films prepared by ECR MOCVD at $450^{\circ}C$ on electron beam and RIE patterned RuO2/TiN storage nodes is finally described.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.1
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• pp.38-42
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• 2001

Electric and dielectric(Ba,Sr)$TiO_3$[BST] thin films for emtal-Insulator-Semiconductor(MIS) capacitors have been studied. BST thin films wre deposted on p-Si(100) substrates bythe RF magnetron sputtering with tempratue range of 500~$600^{\circ}C$. The dielectric properties of MIS capacitors consisting of Al/BST/$SiO_2$/Si sandwich structure were evaluated ot redcue the leakage current density. The charge state densities of the MIS capacitors were determined by high frequency (1 MHz) C-V measurement. In order to reduce the leakage current in MIS capacitor, high quality $SiO_2$ layer was deposited on bare p-Si substrate. Depending on the oxygen pressure and substrate temperature both positive and negative polarities of effective oxide charge in the MIS capacitors were evaluated. It is considered that the density of electronic states, generated at the BST/$SiO_2$/p-Si interface due to the asymmetric structure within BST/$SiO_2$/Si structure, and the oxygen vacancy content has influence on the behavior of oxide charge.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03a
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• pp.21-21
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• 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 $400^{\circ}C$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.5
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• pp.696-702
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• 2002

The BST $({Bal-xSrxTiO_3})$ (50/50) thin film has been grown by RF magnetron reactive sputtering and its characteristics such as crystallization, surface roughness, and electrical properties have been investigated with varying the film thickness. The crystallization and surface roughness of BST thin film are investigated by using XRD and AFM, respectively. The BST thin film annealed at $800^{\circ}C$ for 2 min has pure perovskite structure and good surface roughness of 16.1$\AA$. As the film thickness increases from 80 nm to 240 nm, the dielectric constant at 10 KHz increases from 199 to 265 and the leakage current density at 250 ㎸/cm decreases from $0.779 {\mu}A/{cm^2} to 0.184 {\mu}A/{cm^2}$. In the case of 240 nm-thick BST thin film, the charge storage density and leakage current density at 5V are 50.5 fC/${{\mu}m^2} and 0.182 {\mu}A/{cm^2}$, respectively. The values indicate that the BST thin film is a very useful dielectric material for the DRAM capacitor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.236-236
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• 2008

(Bi,La)$Ti_3O_{12}$(BLT) thin film is one of the most attractive materials for ferroelectric random access memory (FRAM) applications due to its some excellent properties such as high fatigue endurance, low processing temperature, and large remanent polarization [1-2]. The authors firstly investigated and reported the damascene process of chemical mechanical polishing (CMP) for BLT thin film capacitor on behalf of plasma etching process for fabrication of FRAM [3]. CMP process could prepare the BLT capacitors with the superior process efficiency to the plasma etching process without the well-known problems such as plasma damages and sloped sidewall, which was enough to apply to the fabrication of FRAM [2]. BLT-CMP characteristics showed the typical oxide-CMP characteristics which were related in both pressure and velocity according to Preston's equation and Hernandez's power law [2-4]. Good surface roughness was also obtained for the densification of multilevel memory structure by CMP process [3]. The well prepared BLT capacitors fabricated by CMP process should have the sufficient ferroelectric properties for FRAM; therefore, in this study the electrical properties of the BLT capacitor fabricated by CMP process were analyzed with the process parameters. Especially, the effects of CMP pressure, which had mainly affected the removal rate of BLT thin films [2], on the electrical properties were investigated. In order to check the influences of the pressure in eMP process on the ferroelectric properties of BLT thin films, the electrical test of the BLT capacitors was performed. The polarization-voltage (P-V) characteristics show a decreased the remanent polarization (Pr) value when CMP process was performed with the high pressure. The shape of the hysteresis loop is close to typical loop of BLT thin films in case of the specimen after CMP process with the pressures of 4.9 kPa; however, the shape of the hysteresis loop is not saturated due to high leakage current caused by structural and/or chemical damages in case of the specimen after CMP process with the pressures of 29.4 kPa. The leakage current density obtained with positive bias is one order lower than that with negative bias in case of 29.4 kPa, which was one or two order higher than in case of 4.9 kPa. The high pressure condition was not suitable for the damascene process of BLT thin films due to the defects in electrical properties although the better efficiency of process. by higher removal rate of BLT thin films was obtained with the high pressure of 29.4 kPa in the previous study [2].

• Bulletin of the Korean Chemical Society
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• v.23 no.5
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• pp.741-744
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• 2002

Single phase of multicomponent oxide ZrTiO4 film could be prepared through surface sol-gel route simply by coating the mixture of 100 mM zirconium butoxide and titanium butoxide on $Pt/Ti/SiO_2Si(100)$ substrate, following pyro lysis at $450^{\circ}C$, and annealing it at 770 $^{\circ}C.$ The dielectric constant of the film was reduced as the film thickness decreased due to of the interfacial effects caused by layer/electrode and a few voids inside the multilayer. However, the dielectric property was independent of applied dc bias sweeps voltage (-2 to +2 V).The dielectric constant of bulk film, 31.9, estimated using series-connected capacitor model was independent of film thickness and frequency in the measurement range, but theoretical interfacial thickness, ti, was dependent on the frequency. It reached a saturated ti value, $6.9{\AA}$, at high frequency by extraction of some capacitance component formed at low frequency range. The dielectric constant of bulk ZrTiO4 pellet-shaped material was 33.7 and very stable with frequency promising as good applicable devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.404-407
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• 2003

Among the ferroeletric thin films that have been widely investigated for ferroelectric random access memory (FRAM) applications, the $SrBi_2Ta_2O_9$ (SBT) thin film is appropriate as a memory capacitor material due to its excellent fatigue endurance. SBT thin films were etched in high-density $Cl_2/Ar$ in inductively coupled plasma. The maximum etch rate of SBT film is $1834\;{\AA}/min$ under $Cl_2/(Cl_2+Ar)$ of 30 %, rf power of 700 W, dc-bias voltage of -250 V, chamber pressure of 11 mTorr and gas flow rate of 20 sccm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.402-405
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• 1999

The Study of this paper is to establish the optimum fabricating condition of specimens using Vapor Deposition Polymerization Method which belongs to a mode of preparation of functional organic thin films with dry process and to develop thin film type humidity sensor which has good humidity sensitive Characteristics. Scanning electron microscopy Atomic force microscopy were used to analyze the characteristics of thin film and the basic structure of the humidity sensor is a parallel capacitor which consists of three layers of Al/PI/Al. The characteristics of fabricated samples were measured under various conditions and obtained linear characteristics in the range of 20∼80%RH independent of temperature change and low hysteresis characteristics.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.5
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• pp.185-190
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• 2002

Capacitor material utilized in the downsizing passive devices and dynamic random access memory(DRAM) requires the physical and electrical properties at given area such as capacitor thickness reduction, relative dielectric constant increase, low leakage current and thermal stability. Common capacitor materials, $SiO_2$, $Si_3N_4$, $SiO_2$/$Si_3N_4$,TaN and et al., used until recently have reached their physical limits in their application to several hundred angstrom scale capacitor. $Ta_2O_{5}$ is known to be a good alternative to the existing materials for the capacitor application because of its high dielectric constant (25 ~35), low leakage current and high breakdown strength. Despite the numerous investigations of $Ta_2O_{5}$ material, there have little been established the clear understanding of the annealing effect on capacitance characteristic and conduction mechanism, design and fabrication for $Ta_2O_{5}$ film capacitor. This study presents the structure-property relationship of reactive-sputtered $Ta_2O_{5}$ MIM capacitor structure processed by annealing in a vacuum. X-ray diffraction patterns skewed the existence of amorphous phase in as-deposited condition and the formation of preferentially oriented-$Ta_2O_{5}$ in 670, $700^{\circ}C$ annealing. On 670, $700^{\circ}C$ annealing under the vacuum, the leakage current decrease and the enhanced temperature-capacitance characteristic stability. and the leakage current behavior is stable irrespective of applied electric field. The results states that keeping $Ta_2O_{5}$ annealed at vacuum gives rise to improvement of electrical characteristics in the capacitor by reducing oxygen-vacancy and the broken bond between Ta and O.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.570-573
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• 2002

Pb(Zr0.52Ti0.48)O3 (PZT) thin films were deposited on the Pt/Ti bottom electrode by rf magnetron sputtering method from target containing 5%, 25% and 50% Pb excess for applying ferroelectric random access memory (FRAM). PZT films were deposited at $300^{\circ}C$ and then they were crystallized by rapid thermal annealing (RTA) at $700^{\circ}C$. After RTA treatment, our results showed that all PZT films indicated perovskite polycrystalline structure with preferred orientation (110) and no pyrochlore phase was observed by X-ray diffraction (XRD) and by Scanning electron microscopy (SEM). A well-fabricated PZT film of excess Pb 25% capacitor showed a leakage current density in the order of $2.63{\times}10^{-7}A/cm^2$ at 100kV/cm, a remanent polarization of $3.385{\mu}C/cm^2$ and a coercive field of 41.32 kV/cm. The results showed that Pb excess of target affects to electrical properties of PZT thin film.