• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.734-737
• /
• 2004

The metal-ferroelectric-semiconductor (MFS) structure is widely studied for nondestructive readout (NDRO) memory devices, but conventional MFS structure has a critical problem. It is difficult to obtain ferroelectric films like PZT on Si substrate without interdiffusion of impurities such as Pb, Ti and other elements. In order to solve these problems, the metal-ferroelectric-insulator-semiconductor (MFIS) structure has been proposed with a buffer layer of high dielectric constant such as MgO, $Y_2O_3$, and $CeO_2$. In this study, the etching characteristics (etch rate, selectivity) of MgO thin films were etched using $Cl_2/Ar$ plasma. The maximum etch rate of 85 nm/min for MgO thin films was obtained at $Cl_2$(30%)/Ar(70%) gas mixing ratio. Also, the etch rate was measured by varying the etching parameters such as ICP rf power, dc-bias voltage, and chamber pressure. Plasma diagnostics was performed by Langmuir probe (LP) and optical emission spectroscopy (OES).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.47-50
• /
• 2000

This paper investigated structural and electrical properties of $Y_2$ $O_3$ as a buffer layer of single transistor FRAM (ferroelectric RAM). $Y_2$ $O_3$ buffer layers were deposited at a low substrate temperature below 40$0^{\circ}C$ and then RTA (rapid thermal anneal) treated. Investigated parameters are substrate temperature, $O_2$ partial pressure, post-annealing temperature, and suppression of interfacial $SiO_2$ layer generation. For a well-fabricated sample, we achieved that leakage current density ( $J_{leak}$) in the order of 10$^{-7}$ A/$\textrm{cm}^2$, breakdown electric field ( $E_{br}$ ) about 2 MV/cm for $Y_2$ $O_3$ film. Capacitance versus voltage analysis illustrated dielectric constants of 7.47. We successfully achieved an interface state density of $Y_2$ $O_3$/Si as low as 8.72x1010 c $m^{-2}$ e $V^{-1}$ . The low interface states were obtained from very low lattice mismatch less than 1.75%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.5
• /
• pp.388-392
• /
• 2002

In this work, the etching of $CeO_2$ thin films has been performed in an inductively coupled $Ar/CF_4/Cl_2$ plasma. The highest etch rate of the $CeO_2$ thin film ws 250 ${\AA}/min$ and the selectivity of CeO$_2$to SBT was 0.4 at a 10% additive $Cl_2$ into Ar/($Ar+CF_4$)gas mixing ratio of 0.8. From result of X-ray photoelectron spectroscopy (XPS) analysis, there are Ce-Cl and Ce-F bonding by chemical reaction between Cl, F and Ce. During the etching of $CeO_2$ thin films in $Ar/CF_4/Cl_2$ plama, Ce-Cl and Ce-F bond is formed, and these prodcuts can be removed by the physical bombardment of Ar ions. The 10% additive $Cl_2$ into the Ar/($Ar+CF_4$)gas mixing ratio of 0.8 could enhance the reaction between Cl, F and Ce.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.11a
• /
• pp.25-28
• /
• 2000

In this study, $Y_2$O$_3$ thin films were etched with inductively coupled plasma (ICP). The etch rate of $Y_2$O$_3$, and the selectivity of $Y_2$O$_3$ to YMnO$_3$ were investigated by varying Cl$_2$/(Cl$_2$+Ar) gas mixing ratio. The maximum etch rate of $Y_2$O$_3$, and the selectivity Of $Y_2$O$_3$ to YMnO$_3$ were 302/min, and 2.4 at Cl$_2$/(Cl$_2$+Ar) gas mixing ratio of 0.2 repectively. In x-ray photoelectron spectroscopy (XPS) analysis, $Y_2$O$_3$ thin film was dominantly etched by Ar ion bombardment, and was assisted by chemical reaction of Cl radical. These results were confirmed by secondary ion mass spectroscopy(SIMS) analysis. YCI, and YCl$_3$ existed at 126.03 a.m.u, and 192.3 a.m.u, respectively

• The Journal of Asian Finance, Economics and Business
• /
• v.8 no.5
• /
• pp.807-815
• /
• 2021

Microfinance is seen as a tool for poverty elimination by providing various services characterized as financial and non-financial to minority groups in the society to be included in the mainstream financial system. This paper seeks to examine the effect of microfinance institutions' (MFIs) financial and non-financial services on women's entrepreneurship and empowerment in Jordan as a developing country. To gain a deeper understanding of the effectiveness of microfinance services, the study is undertaken to address the question of what kinds of services are available and whether the MFI services are in line with the actual needs of women entrepreneurs to improve their performance. Hence, a qualitative approach was adopted in this study using semi-structured interview questions to collect data from twenty-four women entrepreneurs in Jordan. The results showed that, as regards financial services, the most important needs of women entrepreneurs include providing adequate financing with necessary financial facilities such as reducing interest, reducing monthly installments, and extending the grace period, while non-financial services should include holding specialized courses, accessing a counseling center, providing incentives and psychological support, marketing support, and monitoring and evaluation. This study concluded that factors associated with MFI play a crucial role to uplift women entrepreneurs and eliminate gender inequality.

• Electrical & Electronic Materials
• /
• v.16 no.9
• /
• pp.64.1-64
• /
• 2003

A metal-ferroelectric [SrBi$_2$Ta$_2$O$\_$9/ (SBT)-high-k-insulator(PrOx)-semiconductor(Si) structure has been fabricated and evaluated as a key part of metal-ferroelectric-insulator-semiconductor-field-effect-transistor MFIS-FET memory, aiming to improve the memory retention characteristics by increasing the dielectric constant in the insulator layer and suppressing the depolarization field in the SBT layer. A 20-nm PrOx film grown on Si(100) showed both a high of about 12 and a low leakage current density of less than 1${\times}$ 10e-8 A/$\textrm{cm}^2$ at 105 MV/cm. A 400-nm SBT film prepared on PrOx/Si shows a preferentially oriented (105) crystalline structure, grain size of about 130 nm and subface roughness of 3.2 nm. A capacitance-voltage hysteresis is confirmed on the Pt/SBT/PrOx/Si diode with a memory window of 0.3V at a sweep voltage width of 12 V. The memory retention time was about 1 104s, comparable to the conventional Pt/SBT/SiO$\_$x/N$\_$y/(SiO$\_$N/)/Si. The gradual change of the capacitance indicates that some memory degradation mechanism is different from that in the Pt/SBT/SiON/Si structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.9
• /
• pp.695-699
• /
• 2001

Cerium dioxide (CeO$_2$) was used as the intermediate layer between the ferroelectric thin film and Si substrate in a metal-ferroelectric-semiconductor field effect transistor (MFSFET), to improve the interface property by preventing the interdiffusion of the ferroelectric material and the Si substrate. In this study, CeO$_2$ thin films were etched with a CF$_4$/Ar gas combination in inductively coupled plasma (ICP). The maximum etch rate of CeO$_2$ thin films was 270$\AA$/min under CF$_4$/(CF$_4$+Ar) of 0.2, 600 W/-200V, 15 mTorr, and $25^{\circ}C$. The selectivities of CeO$_2$ to PR and SBT were 0.21, 0.25, respectively. The surface reaction in the etching of CeO$_2$ thin films was investigated with x-ray photoelectron spectroscopy (XPS). There is a chemical reaction between Ce and F. Compounds such as Ce-F$_{x}$ remains on the surface of CeO$_2$ thin films. Those products can be removed by Ar ion bombardment. The results of secondary ion mass spectrometry (SIMS) were consistent with those of XPS. Scanning electron microscopy (SEM) was used to examine etched profiles of CeO$_2$ thin films. The etch profile of over-etched CeO$_2$ films with the 0.5${\mu}{\textrm}{m}$ line was approximately 65$^{\circ}$.>.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.38 no.12
• /
• pp.8-13
• /
• 2001

Cerium oxide ($CeO_2$) thin film has been proposed as a buffer layer between the ferroelectric thin film and the Si substrate in Metal-Ferroelectric-Insulator-Silicon (MFIS) structures for ferroelectric random access memory (FRAM) applications. In this study, $CeO_2$ thin films were etched with $Cl_2$/Ar gas mixture in an inductively coupled plasma (ICP). Etch properties were measured for different gas mixing ratio of $Cl_2$($Cl_2$+Ar) while the other process conditions were fixed at RF power (600 W), dc bias voltage (-200 V), and chamber pressure (15 mTorr). The highest etch rate of $CeO_2$ thin film was 230 ${\AA}$/min and the selectivity of $CeO_2$ to $YMnO_3$ was 1.83 at $Cl_2$($Cl_2$+Ar gas mixing ratio of 0.2. The surface reaction of the etched $CeO_2$ thin films was investigated using x-ray photoelectron spectroscopy (XPS) analysis. There is a Ce-Cl bonding by chemical reaction between Ce and Cl. The results of secondary ion mass spectrometer (SIMS) analysis were compared with the results of XPS analysis and the Ce-Cl bonding was monitored at 176.15 (a.m.u). These results confirm that Ce atoms of $CeO_2$ thin films react with chlorine and a compound such as CeCl remains on the surface of etched $CeO_2$ thin films. These products can be removed by Ar ion bombardment.

• Pediatric Infection and Vaccine
• /
• v.19 no.1
• /
• pp.1-11
• /
• 2012

Purpose : Although influenza is regarded as one of the major causes of morbidity and mortality in children with cancer, the actual vaccine coverage remains poor. We conducted evaluation of immunogenicity and safety of influenza vaccine in children with cancer. Methods : In this study, 25 children with cancer who received influenza vaccine (SK influenza IX vaccine$^{(R)}$) at the Korea Cancer Center Hospital between October and December 2009 were analyzed. Blood samples of patients were collected twice (at the beginning of this study and at 30th day after vaccination) and their antibody titers were measured using the hemagglutination-inhibition (HI) assay. Immunogenicity of the influenza vaccine was assessed by seroprotection rate on days 0 and 30, seroconversion rate on day 30, and mean fold increase (MFI) of geometric mean titer (GMT) of HI between days 0 and 30. Results : Any of the subjects in our study did not experienced serious adverse events after influenza vaccination. Seroprotection rates were 68% for H1N1, 40% for H3N2, and 36% for B. Seroconversion rates were 12% for H1N1, 16% for H3N2, and 20% for B. MFIs were 0.9 for H1N1, 1.2 for H3N2, and 1.8 for B. Conclusion : In the study, we found a limited protective immune response to influenza vaccine, among subjects with cancer. However, some subjects showed seroconversion, and there were no severe adverse events among all subjects, supporting the recommendation of annual influenza vaccination in children with cancer.

• Journal of the Microelectronics and Packaging Society
• /
• v.9 no.4
• /
• pp.11-16
• /
• 2002

In this study, the dry etching characteristics of $SrBi_2Ta_2O_9$ (SBT) thin films were investigated by using ICP-RIE (inductively coupled plasma-reactive ion etching). The etching damage and degradation were analyzed with XPS (X-ray photoelectron spectroscopy) and C-V (Capacitance-Voltage) measurement. The etching rate increased with increasing the ICP power and the capacitively coupled plasma (CCP) power. The etch rate of 900$\AA$/min was obtained with 700 W of ICP power and 200 W of CCP power. The main problem of dry etching is the degradation of the ferroelectric material. The damage-free etching characteristics were obtained with the $Ar/C1_2/CHF_3$ gas mixture of 20/14/2 when the ICP power and CCP power were biased at 700 W and 200 W, respectively. The experimental results show that the dry etching process with ICP-RIE is applicable to the fabrication of the single transistor type ferroelectric memory device.