• Journal of IKEEE
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• v.28 no.1
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• pp.110-115
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• 2024

This paper analyzed the V_th (Threshold Voltage) variations in 3D NAND Flash memory with tapered O/N/O (Oxide/Nitride/Oxide) structure and O/N/F (Oxide/Nitride/Ferroelectric) structure, where the blocking oxide is replaced by ferroelectric material. With a tapering angle of 0°, the O/N/F structure exhibits lower resistance compared to the O/N/O structure, resulting in reduced V_th variations in both the upper and lower regions of the WL (Word Line). Tapered 3D NAND Flash memory shows a decrease in channel area and an increase in channel resistance as it moves from the upper to the lower WL. Consequently, as the tapering angle increases, the V_th decreases in the upper WL and increases in the lower WL. The tapered O/N/F structure, influenced by V_fe proportional to the channel radius, leads to a greater reduction in V_th in the upper WL compared to the O/N/O structure. Additionally, the lower WL in the O/N/F structure experiences a greater increase in V_th compared to the O/N/O structure, resulting in larger V_th variations with increasing tapering angles.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.1
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• pp.1-14
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• 2001

Current status and prospects of FET-type FeRAMs (ferroelectric random access memories) are reviewed. First, it is described that the most important issue for realizing FET-type FeRAMs is to improve the data retention characteristics of ferroelectric-gate FETs. Then, necessary conditions to prolong the retention time are discussed from viewpoints of materials, device structure, and circuit configuration. Finally, recent experimental results related to the FET-type memories are introduced, which include optimization of a buffer layer that is inserted between the ferroelectric film and a Si substrate, development of a new ferroelectric film with a small remnant polarization value, proposal and fabrication of a 1T2C-type memory cell with good retention characteristics, and so on.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.10
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• pp.865-870
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• 2003

The MFIS (Metal-Ferroelectric-Insulator-Semiconductor) capacitors were fabricated using a metalorganic decomposition method. Thin layers of CeO$_2$ were deposited as a buffer layer on Si substrate and BLT thin films were used as a ferroelectric layer. The electrical and structural properties of the MFIS structure were investigated. X -ray diffraction was used to determine the phase of the BLT thin films and the quality of the CeO$_2$ layer. The morphology of films and the interface structures of the BLT and the CeO$_2$ layers were investigated by scanning electron microscopy. The width of the memory window in the C-V curves for the MFIS structure is 2.82 V. The experimental results show that the BLT-based MFIS structure is suitable for non-volatile memory FETs with large memory window.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.403-405
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• 2000

This paper describes a single transistor type ferroelectric field effect transistor (1Tr FeFET) memory cell scheme, which select one unit memory cell and program/read it. The well voltage can be controlled by isolating the common row well lines. Through applying bias voltage to Gate and Well, respectively, we implement If FeFET memory cell scheme in which interference problem is not generated and the selection of each memory cell is possible. The results of HSPICE simulations showed the successful operations of the proposed cell scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.9
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• pp.1717-1723
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• 2007

In this study , quasi-MFISFET (Metal-Ferroelectric-Insulator-Semiconductor FET) devices are fabricated using PLZT(10/30/70), PLT(10), PZT(30/70) thin film and their drain current properties are investigated. It is found that the drain current of quasi-MFISFET is directly influenced by the polarization strength of ferroelectric thin fan. Also, when the gate voltages are ${\pm}5\;and\;{\pm}10V$, the memory windows are 0.5 and 1.3V, respectively. It means that the memory window is changed with the variation of coercive voltage generated by the voltage applied on ferroelectric thin film. The electric field and the leakage current with time delay of PLZT(10/30/70) thin lam are measured to investigate the retention property of MFISFET device. Some material parameters such as current density constant, $J_{ETO}$, electric field dependent factor K and time dependent factor m are obtained. The variation of charge density with time is quantitatively analyzed by using the material parameters.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.180-180
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• 2003

FRAM (Ferroelectric Random Access Memory)은 DRAM(Dynamic Random Access Memory)in 커패시터 재료을 상유전체 물질에서 강유전체 물질로 대체하여 전원 공급이 차단되어도 정보를 기억할 수 있고, 데이터의 고속처리가 가능하고 저소비전력과 집적화가 뛰어난 차세대 메모리 소자이다. 본 연구에서는 n-Well/P-Si(100) 기판위에 $Y_2$O$_3$ 박막을 중간층 (buffer layer)으로 사용하여 (Bi,La) Ti$_3$O$_{12}$ (BLT) 강유전체 박막을 졸-겔 방법으로 형성하여 MFM(I)S(Metal Ferroelectric Metal (Insulation) Silicon) 구조의 커패시터 및 전계효과형 트랜지스터(Field Effect Transistor) 소자를 제작하였다. 제작된 소자에 대해 형상학적, 전기적 특성을 조사, 분석하였다.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.237-237
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• 2006

P(VDF/TrFE(72/28) ultrathin films were used in the fabrication of Metal-Ferroelectric polymer-Metal (MFM) single bit device with special emphasis on uniform film surface, faster dipole switching time under applied external field and longer memory retention time. AFM and FTIR-GIRAS were complementary in analyzing surface crystalline morphology and the resultant change in chain orientation with varying thermal history. DC-EFM technique was used to 'write-read-erase' the data on the memory bit in a much faster time than P-E studies. The results obtained from this study will enable us to have a good understanding of the ferroelectric and piezoelectric behavior of P(VDF/TrFE)(72/28) thin films suitable for high density data storage applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.9
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• pp.725-728
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• 2000

Ferroelectric thin film capacitors with high dielectric constant are important for the application of memory devices. In this work, We have systematically investigated the variation of grain sizes depending on the process condition of two-step process. Both in-situ annealing and ex-annealing have been compared depending on the annealing time. C-V measurement, ferroelectric properties, leakage current, XRD and SEM were performed to investigate the electircal properties and microstructural properties of Pb(La, Ti)O$_3$ films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.3
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• pp.200-205
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• 2000

This paper describes the structure modeling and operation characteristics of MFMIS(metal-ferroelectric-metal-insulator-semiconductor) device using the Tsuprem4 which is a semiconductor device tool by Avanti. MFMIS device is being studied for nonvolatile memory application at various semiconductor laboratory but it is difficult to fabricate and analyze MFMIS devices using the semiconductor simulation tool: Tsuprem4, medici and etc. So the new library and new materials parameters for adjusting ferroelectric material and platinum electrodes in the tools are studied. In this paper structural model and operation characteristics of MFMIS devices are measured, which can be easily adopted to analysis of MFMIS device for nonvolatile memory device application.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.861-864
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• 2000

Ferroelectric thin film capacitors with high dielectric constant are important for the application of memory devices. In this work, thin films of PLT(28)(Pb$\sub$0.72/La$\sub$0.28/Ti$\sub$0.93/O$_3$) were fabricated on Pt/Ti/SiO$_2$/Si substrates in-situ annealing and ex-situ annealing have been compared depending on the annealing time. We have systematically investigated the variation of grain sizes depending on the condition of post-annealing and the variation of deposition rate. C-V measurement, ferroelectric properties, leakage current and SEM were performed to investigate the electrical properties and the microstructural properties of Pb(La,Ti)O$_3$.