• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.106-106
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• 2000

반도체 소자가 미세화 됨에 따라 게이트 유전막으로 사용되는 SiO2의 박막화가 요구되나, boron penetration에 의한 Vt shift, 게이트 누설전류, 다결정 실리콘 게이트의 depletion effect 그리고 quantum mechanical effect 때문에 ~20 급에서 한계를 나타내고 있다. 이에 0.1$\mu\textrm{m}$이상의 design rule을 갖는 logic이나 memory 소자에서 요구되어지는 ~10 급 게이트 산화막은 SiO2(K=3.9)를 대신하여 고유전율을 갖는 재료의 채택이 필수 불가결하게 되었다. 고유전 박막 재료를 사용하면, 두께를 두껍게 해도 동일한 inversion 특성이 유지되고 carrier tunneling 이 덜하여 등가 산화막의 두께를 줄일 수 있다. 이러한 고유전박막 재료중 가장 활발히 연구되고 있는 재료는 Ta2O5, Al2O3, STO 그리고 BST 등이 있으나 Ta2O5, STO, BST 등은 실리콘 기판과 직접 반응을 한다는 문제를 가지고 있으며, Al2O3는 유전율이 낮의 재료가 최근 주목받고 있다. 본 실험에서는 ZrO2, HfO2 또는 그 silicates 등의 재료가 최근 주목 받고 있다. 본 실험에서는 ZrO2 박막의 증착조건에 따른 물리적, 전기적 특성 변화에 대하여 연구하였다. RCA 방식으로 세정한 P-type (100) 실리콘 기판위에 reactive DC sputtering 방법으로 압력 5mtorr, power 100~400W, 기판온도는 100-50$0^{\circ}C$로 변화시켜 ZrO2 박막을 증착한 후 산소와 아르곤 분위기에서 400-80$0^{\circ}C$, 10-120min으로 열처리하였다. 증착직후의 시편들과 열처리한 ZrO2 박막의 미세구조와 전기적 특성 변화를 관찰하였다. 우선 굴절율(RI)를 이용해 ZrO2 박막의 밀도를 예측하여 power와 기판온도에 따라 이론값 2.0-2.2 에 근접한 구조를 얻은 후 XRD, XPS, AFM, 그리고 TEM을 사용하여 ZrO2 박막의 chemical bonding, surface roughness 그리고 interfacial layer의 특성을 관찰하였다. 그리고 C-V, I-V measurement를 이용해 capacitance, 유전율, 누설전류 등의 전기적 특성을 관찰해 최적 조건을 설정하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.94-98
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• 2000

Polycrystalline SBTN ferroelectric thin films were prepared by sol-gel method with various Nb mole ratios on Pt/ $SiO_2$/Si (100) substrates. The films were annealed at different temperatures and characterized in terms of phase and microstructure. Relatively a well saturated hysteresis pattern was obtained at x =0.2 in S $r_{0.8}$B $i_{2.3}$(T $a_{1-x}$ N $b_{x}$)$_2$ $O_{9+}$$\alpha$/ thin films. At an applied voltage of 5V, the dielectric constant ($\varepsilon$$_{r}$) and dissipation factor (tan $\delta$) of typical S $r_{0.8}$B $i_{2.3}$(T $a_{1-x}$ N $b_{x}$)$_2$ $O_{9+}$$\alpha$/ thin film (x=0.2) were about 236.2 and 0.034. Measured remanent polarization (2Pr) and coercive field (Ec) were 4.28C/c $m_2$, and 38.88kv/cm respectively. No fatigue was observed up to 6$\times$10$_{10}$ switching cycles at 5V and the normalized polarization reduced by a factor of only 4%.%. 4%.%. 4%.%.%.%.%.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.276-276
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• 2014

High-performance, fully-transparent, and top-gated oxide thin-film transistor (TFT) was successfully fabricated with Ta2O5 high-k gate dielectric on a glass substrate. Through a self-passivation with the gate dielectric and top electrode, the top-gated oxide TFT was not affected from H2O and O2 causing the electrical instability. Heat-treated InSnO (ITO) was used as the top and source/drain electrode with a low resistance and a transparent property in visible region. A InGaZnO (IGZO) thin-film was used as a active channel with a broad optical bandgap of 3.72 eV and transparent property. In addition, using a X-ray diffraction, amorphous phase of IGZO thin-film was observed until it was heat-treated at 500 oC. The fabricated device was demonstrated that an applied electric field efficiently controlled electron transfer in the IGZO active channel using the Ta2O5 gate dielectric. With the transparent ITO electrodes and IGZO active channel, the fabricated oxide TFT on a glass substrate showed optical transparency and high carrier mobility. These results expected that the top-gated oxide TFT with the high-k gate dielectric accelerates the realization of presence of fully-transparent electronics.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.181-184
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• 1993

Microwave characteristics of the system (Zr, Sn)$TiO_4$, ceramics within composition range X between 0.2 and 0.35 were investigated at 8GHz. For the improvement properties of (Zr, Sn)$TiO_4$, system, $Ta_2O_5$ and $WO_3$ addition in the range of 0.5 to 2.0wt% were investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.122.1-122.1
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• 2015

The dependence of electronic properties and local structure of tantalum oxide thin film on oxygen deficiency have been investigated by means of X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and X-ray absorption spectroscopy (XAS). The XPS results showed that the oxygen flow rate change results in the appearance of features in the Ta 4f at the binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV whose peaks are attributed to Ta1+, Ta2+, Ta3+, Ta4+, and Ta5+, respectively. The presence of nonstoichiometric state from tantalum oxide (TaOx) thin films could be generated by the oxygen vacancies. The REELS spectra suggested the decrease of band gap for tantalum oxide thin films with increasing oxygen deficiency. In addition, XAS spectra manifested both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the decrease of oxygen deficiency.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.145-145
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• 1997

Recent progress of electric technology requires new piezoelectric crystals having superior properties such as zero temperature coefficients and large electromechanical coupling factors. We have developed a series of new leading chandidates, La$_3$Ga5SiO14(langasite, LGS), La3Nb0.5Ga5.5O14(LNG), La3Ta0.5O14(LTG), to satisfy those requirements. High quality LGS, LNG and LTG single crystals, with dimensions of 2 inches in diameter, were successfully grown by the Czochralski method at a pulling rate of 1mm/h. Since no variation of chemical composition was observed when whole melt in a crucible was crystallized, congruency of these compositions was confirmed. Physical constants such as elastic constants, dielectric constants and piezoelectric constants were measured. Filters and oscillators made of grown LGS, LNG and LTG single crystals showed superior properties such as three times wider passband than that of quartz, low insertion loss and easy processing, Langasite family crystals were shown to be superior materials to other known materials such as quartz, LiTaO$_3$, $\alpha$-AlPO$_4$ and Li$_2$B$_4$O7.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.1
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• pp.7-15
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• 2004

The ferroelectric SBT thin films as a material of capacitors for non-volatile FRAMs have some problems that its remanent polarization value is relatively low and the crystallization temperature is quite high abovc 80$0^{\circ}C$. Therefore, in this paper, SBTN solution with S $r_{0.9}$B $i_{2.1}$T $a_{1.8}$N $b_{0.2}$$O_{9}$ composition was synthesized by sol-gel method. Sr(O $C_2$ $H_{5}$)$_2$, Bi(TMHD)$_3$, Ta(O $C_2$ $H_{5}$)$_{5}$and Nb(O $C_2$ $H_{5}$)$_{5}$ were used as precursors, which were dissolved in 2-methoxyethanol. SBTN thin films with 200 nm thickness were deposited on Pt/Ti $O_2$/ $SiO_2$/Si substrates by spin-coating. UV-irradiation in a power of 200 W for 10 min and rapid thermal annealing in a 5-Torr-oxygen ambient at 76$0^{\circ}C$ for 60 sec were used to promote crystallization. The films were well crystallized and fine-grained after annealing at $650^{\circ}C$ in oxygen ambient. The electrical characteristics of 2Pr=11.94 $\mu$C/$\textrm{cm}^2$, Ps＋/Pr＋=0.54 at the applied voltage of 5 V were obtained for a 200-nm-thick SBTN films. This results show that 2Pr values of the UV irradiated and rapid thermal annealed SBTN thin films at the applied voltage of 5 V were about 57% higher than those of no additional processed SBTN thin films. thin films.lms.s.s.

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.806-811
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• 2003

Ultrafine TaC powders were synthesised by spray drying using tantalum oxalate solution. The spray dried powders were spherical shape and less than 30 $\mu\textrm{m}$ in size. The powders calcined at 500 and X$700^{\circ}C$ showed amorphous structures and $Ta_2$$O_{5}$ phase was obtained by calcining at $700^{\circ}C$. The particle size and shape remains constant after calcination. The calcined spherical powders were composed of an agglomerate of primary particles under 50 nm in size. The complete formation of TaC could be achieved by heat treatment at $1050^{\circ}C$ for 6 hrs. The observed size of TaC powders by TEM was less than 200 nm.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.254-254
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• 2012

The purposed of this work was to determine surface charateristics of anodized Ti-30Nb-xTa alloys with Ta content. Samples were prepared by arc melting, followed by followed by homogenization for 12 hr at $1000^{\circ}C$ in argon atmosphere. The electrolyte for anodization treatment was prepared by mixing 465ml $H_2O$ with 35M $H_3PO_4$ and anodized at 180V to 220V. The microstructures of the alloys were examined by X-ray diffractometer (XRD) and optical microscopy (OM). Surface characteristics of anodized Ti-30Nb-xTa alloys was investigated by potentiodynamic test and potentiostatic in 0.9% Nacl solution at $36.5{\pm}1^{\circ}C$. It was observed that the changed ${\alpha}$ phase to ${\beta}$ phase with Ta content.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.87-91
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• 2004

We have investigated the effects of W-N/Pt bottom electrode on the ferroelectric degradation of $Sr_{0.8}Bi_{2.4}Ta_2O_9(SBT)/Pt$ due to hydrogen annealing at $350^{\circ}C$ in $N_2$ gas atmosphere containing $5{\%}\;H_2$ gas for 1hr. As a result, inserting the W-N thin films between SBT and Pt, this W-N thin film prevents hydrogen molecules to be chemisorbed at the Pt electrode surface of at the electrode/ferroelectric interface during hydrogen annealing. These hydrogen atoms can diffuse into the SBT and react with the oxide causing the oxygen deficiency in the SBT film, which will result in the ferroelectric degradation. Experimental results show that W-N thin film is a good diffusion barrier during the hydrogen annealing.