Processing and Characterization of Ultra-thin Poly-crystalline Silicon for Memory and Logic Applications

Eunseon Yu,Youngmin Kim,Junsoo Lee,Yongbeom Cho,Won Jae Lee,Seongjae Cho 대한전자공학회 2018 Journal of semiconductor technology and science Vol.18 No.2

In this work, processing and characterization of ultra-thin poly-Si are performed for memory and logic applications. Ultra-thin poly-Si layers with different thicknesses were prepared on the deposited oxide by low-pressure chemical vapor deposition (LPCVD). Deposited poly-Si were doped through POCl3 gas-phase doping at 900 °C, in which 10-nm thickness was reduced. Afterward, postdeposition annealing (PDA) under different conditions were performed. Thicknesses of deposited poly-Si films were 20, 30, and 50 nm. The following PDA improves the crystallinity, which has been confirmed by high-resolution transmission electron microscopy (HR-TEM) with fast Fourier transform (FFT) imaging and sheet resistivity lowering. Also, superior crystalline film is observed in the thinner film and the bi-directionally arranged domains are obtained from the 40-nm poly-Si film.

한국 대학생 학생성공 측정도구 타당화: 서울 소재 4년제 H 대학 사례를 중심으로

홍은선(Eunseon Hong),조성범(Sungbum Cho),조문석(Munseok Cho) 이화여자대학교 교육과학연구소 2021 교육과학연구 Vol.52 No.1

본 연구는 Schreiner 외(2009)가 개발한 학생성공 측정도구인 ‘성장 지수(thriving quotient)’ 를 한국어로 번안하고 우리나라 4년제 대학생을 대상으로 타당화하여 한국 대학생의 학성성공 수준을 파악하는 데 목적이 있다. 이를 위해 서울 소재 4년제 H 대학의 재학생들을 대상으로 예비조사와 본조사 등 2차에 걸쳐 설문조사를 실시하여 요인구조를 검증하고 문항을 확정하였다. 예비조사를 통한 타당도 검증 결과, 9개 문항을 삭제하고 23개 문항으로 구성된 5개 요인구조 모형(능동적 학습 참여(EL: Engaged Leaning), 학업적 자기결정(AD: Academic Determination), 긍정적 인식(PP: Positive Perspective), 공동체적 시민의식(DC: Diverse Citizenship), 사회적 연결성(SC: Social Connectedness))이 적합한 것으로 나타났다. 확인적 요인분석 결과, 5개 요인구조 모형의 적합도가 높게 나타나 학생성공 척도의 구성이 타당함을 확인하였다. 준거타당도 검증을 위해 2020년 K-NSSE 데이터와 병합하여 ‘유의미한 학습경험’, ‘다양한 그룹과의 교류경험’, ‘자기주도학습’, ‘학업적 자기효능감’, ‘교우관계에 대한 만족도’ 변인과의 상관관계를 분석한 결과 유의미한 상관이 있음을 확인하였다. 이러한 연구 결과는 국내 대학 맥락에서 학생성공을 객관적으로 측정할 수 있는 도구를 타당화함으로써 국내에서 학생성공 개념을 구체화하고 관련 변인을 다각적으로 탐색하도록 한다는 데에서 의의가 있다. 마지막으로 연구결과를 토대로 현장에서의 활용방안과 후속 연구를 위한 제언을 제시하였다. The purpose of this study was to validate the Korean version of the Student Success (Thriving Quotient) Scale developed by Schreiner et al. (2009) and to determine the characteristics of student success of university students in Korea. The preliminary and main surveys were conducted to verify the factor structure and to confirm the questions. As a result of the validity and reliability test through the preliminary survey, a 5-factor model with 23 items was identified according to the factor structure of the original scale: EL (Engaged Leaning), AD (Academic Determination), PP (Positive Perspective), DC (Diverse Citizenship), and SC (Social Connectedness). As a result of a confirmatory factor analysis through the main survey, the fit indices of the five-factor structure model were high, and the construct validity of this scale was supported. Criterion-related validity has been verified by correlations between variables such as significant learning, experiences with diverse groups, self-directed learning, academic self-efficacy, and friendship satisfaction. These results are meaningful in concretizing the concept of student success in Korea and in exploring the variables related to student success in the context of Korean universities. Finally, based on the results of the study, suggestions for practice and further research were presented.

Kubelka-Munk 모델을 이용한 피부 분광반사율 연구

조아라 ( A Ra Cho ),김수지 ( Su Ji Kim ),이준배 ( Jun Bae Lee ),심건영 ( Geon Young Sim ),백민 ( Min Back ),조은슬 ( Eun Seul Cho ),장지희 ( Ji Hui Jang ),장은선 ( Eunseon Jang ),김연준 ( Youn Joon Kim ),유권종 ( Kweon Jong Yoo ) 대한화장품학회 2016 대한화장품학회지 Vol.42 No.1

빛은 피부에서 개개인마다 상이한 반사, 흡수 및 산란 등의 광학적 거동을 보여준다. 특히, 피부에서 빛의 반사는 분광반사율이라는 물리량 측정을 통해 개인의 피부 밝기지표로 널리 활용되어 왔다. 따라서 피부에서 빛의 반사 거동 연구는 개인 맞춤형 화장품, 특히 메이크업 제품 개발에 있어 좀 더 효율적인 처방 개선에 기여하거나 새로운 평가법에 활용될 수 있다. 본 연구에서는 Kubelka-Munk 모델을 이용하여 개인의 피부 특성에 따른 빛의 분광반사율 거동에 대해 다각적인 분석을 수행하였다. 또한, 상기 모델과 기존에 알려진 문헌 정보를 이용하여 개인의 피부 분광반사율에 영향을 줄 수 있는 피부 두께 및 헤모글로빈 등의 다양한 파라미터들에 대한 기여도 분석을 수행하였다. 이를 통해, 일반적인 여성의 피부에서의 분광반사율 이론치를 계산하였고, 분광반사율 실측을 통해 이론치와 실측치 간의 유사성을 확인하였다. Kubelka-Munk 모델을 이용한 피부 분광반사율 연구는 향후 새로운 개인 맞춤형 메이크업 화장품 개발에 유용하게 이용될 수 있을 것으로 사료된다. Light shows various optical behaviors such as reflection, absorption, and scattering on skin for individuals. In particular, reflection of light from the skin has been widely used as the brightness index of the skin of individuals through the measurement of the physical quantity of spectral reflectance. Therefore, the study of light behavior on skin would be useful for the preparation of new evaluation method in the development stage of make-up products. In this study, multi-dimensional analysis for spectral reflectance behavior of light on individual skin was performed using Kubelka-Munk model. Also, we analyzed the contribution of skin parameters such as skin thickness and hemoglobin, which could affect the spectral reflectance, using above model and literature information. Base on this, we calculated the theoretical reflectance of normal women for visual light, which showed good agreement with the measured reflectance. Our study of light propagation in skin based on Kubelka-Munk model provides useful insight for the development of personalized cosmetic in the near future.

SiGe Heterojunction FinFET Towards Tera-Hertz Applications

Yu, Eunseon,Lee, Won-Jun,Jung, Jongwan,Cho, Seongjae 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol. No.

<P>In this work, a novel structure FinFET having an ultra-thin SiGe shell channel forming a heterojunction with Si core is proposed and characterized, with an emphasis on high-speed operation capability in the tera-hertz (THz) regime, by 3-dimensional (3-D) device simulation. The proposed device is operated in the p-type enhancement mode and the ultra-thin SiGe channel confines the mobile holes very effectively by the help of the valence band offset (VBO) between SiGe channel and Si core. The simulations with multiple drift and diffusion models and quantum mechanical models for higher accuracy allow to predict the minimum channel thickness and Ge content of 2 nm and 40%, respectively, for suppressing the hole leakage outflowing over the VBO. Also, scalability was checked down to 5 nm for achieving the upcoming logic technology nodes. Cut-off frequency (f (T) ) and maximum oscillation frequency (f (max)) are obtained to be 240 GHz and 1.04 THz at a low drive voltage as -0.7 V, respectively.</P>

Characterization and Optimization of Inverted-T FinFET Under Nanoscale Dimensions

Yu, Eunseon,Heo, Keun,Cho, Seongjae Institute of Electrical and Electronics Engineers 2018 IEEE transactions on electron devices Vol.65 No.8

<P>In this paper, a p-type inverted-T FinFET (IT FinFET) has been optimally structured. Focus is made on analyzing the inferior characteristics reported from the previously fabricated IT FinFETs, and obtaining better performances through a novel structure. IT FinFET has a higher layout efficiency and can thus provide larger drain current ( <TEX>${I}_{D}$</TEX>) under the same dimension as that of a silicon-on-insulator (SOI) FinFET by securing the extended channels of ultrathin body (UTB) on the field region. We closely observe the leverages of fin width ( <TEX>${W}_{\textsf {fin}}$</TEX>), UTB height ( <TEX>${H}_{\textsf {UTB}}$</TEX>), and gate length ( <TEX>${L}_{g}$</TEX>) on the operation characteristics using a 3-D technology computer-aided design simulation with quantum-mechanical models. <TEX>${W}_{\textsf {fin}}$</TEX> below 10 nm is evaluated to be suitable for strong gate controllability. We first examine a critical <TEX>${H}_{\textsf {UTB}}$</TEX>, beyond which a higher drive current is not obtained even with a greater channel width than that of FinFET. When <TEX>${H}_{\textsf {UTB}} = \textsf {3}$</TEX> and 10 nm, IT FinFET yields 13.3% and 142% of saturation current improvement compared with SOI FinFET under the same footprint. At extremely scaled <TEX>${L}_{g}$</TEX>, although the immunity against short-channel effects is slightly weaker than that of SOI FinFET, optimally designed IT FinFET can produce a higher current and demonstrates shorter intrinsic delay times.</P>

Ultrathin SiGe Shell Channel p-Type FinFET on Bulk Si for Sub-10-nm Technology Nodes

Yu, Eunseon,Lee, Won-Jun,Jung, Jongwan,Cho, Seongjae Institute of Electrical and Electronics Engineers 2018 IEEE transactions on electron devices Vol.65 No.4

<P>In this paper, we propose an ultrathin SiGe shell channel p-type FinFET for sub-10-nm technology nodes. Owing to the large valence band offset (VBO or <TEX>$\Delta {E}_{v}$</TEX>) between SiGe shell and Si fin, a hole quantum well is configured in the high-mobility SiGe region as the major conduction path. The proposed device is optimally designed and characterized in dc and ac. Here, high- <TEX>$\kappa$</TEX>/metal gate is adopted for strong gate controllability and the high degree of freedom in threshold voltage ( <TEX>${V}_{{\text {th}}}$</TEX>) adjustment. For a high reliability, modeling of the mobility ( <TEX>$\mu$</TEX>) and saturation velocity ( <TEX>${v}_{{\text {sat}}}$</TEX>) is carried out for different Ge fractions ( <TEX>${x}$</TEX>). The E<SUB>g</SUB> and VBO are also determined for different <TEX>${x}$</TEX> from empirical data. With the set of modeled values and various quantum-mechanical models, the proposed device has been simulated through rigorous 3-D technology computer-aided design simulation. The designed device shows a high scalability reaching down to L<SUB>g</SUB> = 5 nm. At L<SUB>g</SUB> of 5 nm with a driving voltage (V<SUB>DD</SUB>) of −0.5 V, a current gain cutoff frequency (f<SUB>T</SUB>) = 368.88 GHz, dynamic power = 0.055 fJ/ <TEX>$\mu \text{m}$</TEX>, and an intrinsic delay <TEX>$(\tau) = 0.37$</TEX> ps are achieved. This is confirmed by the potential low-power and high-speed operations with a strong gate controllability.</P>

A Band-Engineered One-Transistor DRAM With Improved Data Retention and Power Efficiency

Yu, Eunseon,Cho, Seongjae,Shin, Hyungsoon,Park, Byung-Gook IEEE 2019 IEEE electron device letters Vol.40 No.4

<P>In this letter, a one-transistor (1T) dynamic random-access memory (DRAM) with SiGe quantum well (QW) is proposed, and its performance is validated through the technology computer-aided design (TCAD) simulation. At the write operation, band-to-band tunneling is used and 1 V or lower programming voltage is realized by inserting the SiGe QW beside the drain. This QW also functions as the storage node, which enhances not only the current sensing margin but also the retention time ( <TEX>$\tau _{{\text {ret}}}$</TEX>) compared with those of all-Si device. At an extremely scaled cell size and sub-10-ns write/erase operations, the proposed device shows 0.2-s-long <TEX>$\tau _{{\text {ret}}}$</TEX> and current ratio > 10<SUP>4</SUP>. It has been verified that a single cycle of 1T DRAM operations consumes only 93.8 fJ.</P>

Decellularized Lymph Node as an Immunomodulatory Platform for Macrophage Polarization and Tissue Repair

Yi Sun CHOI,Eunseon JEONG,Jung Seung LEE,Su Kyeom KIM,Sung-Hyun JO,Yun-Gon KIM,Hak-Joon SUNG,Yoonhee JIN,Seung-Woo CHO 한국생물공학회 2022 한국생물공학회 학술대회 Vol.2022 No.4

Immunomodulatory Extracellular Matrix for Macrophage Polarization and Tissue Regeneration

Yi Sun CHOI,Eunseon JEONG,Jung Seung LEE,Su Kyeom KIM,Sung-Hyun JO,Yun-Gon KIM,Hak-Joon SUNG,Yoonhee JIN,Seung-Woo CHO 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10

Immunomodulation in the local tissue microenvironment plays an important role in macrophage polarization that includes its phenotypic expression and pro-healing function. Here, we demonstrate that a lymph node extracellular matrix (LNEM) derived from porcine lymph node tissues can sufficiently mimic natural lymph node tissue and provide optimal biochemical and biophysical cues for immunomodulation in both two-dimensional (2D) coating system and three-dimensional (3D) hydrogel system. The LNEM with intricate extracellular matrix environment leads to strengthened immunomodulatory effects and a 3D hydrogel system proves to be more effective than 2D coating system. The 3D LNEM induces macrophage elongation and enhances M2-type marker expression. Also, the secretion of anti-inflammatory cytokines are increased and phagocytic function is enhanced in macrophages cultured in 3D LNEM. Finally, the implantation of an LNEM hydrogel in a mouse volumetric muscle loss model facilitates the recruitment of host macrophages to the site of injury and enhances macrophage polarization towards the M2 phenotype, which is ideal for tissue regeneration. Therefore, our findings suggest that 3D immune system-mimicking biomaterials can stimulate M2 macrophage phenotype polarization and give rise to highly functional macrophages, making it a useful platform for tissue modeling and wound healing.

Efficient determination of combined hardening parameters for structural steel materials

Sang Whan Han,Jungho Hyun,EunSeon Cho,Kihak Lee 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.42 No.5

Structural materials can experience large plastic deformation under extreme cyclic loading that is caused by events like earthquakes. To evaluate the seismic safety of a structure, accurate numerical material models should be used. For a steel structure, the cyclic strain hardening behavior of structural steel should be correctly modeled. In this study, a combined hardening model, consisting of one isotropic hardening model and three nonlinear kinematic hardening models, was used. To determine the values of the combined hardening model parameters efficiently and accurately, the improved opposition-based particle swarm optimization (iOPSO) model was adopted. Low-cycle fatigue tests were conducted for three steel grades commonly used in Korea and their modeling parameters were determined using iOPSO, which was first developed in Korea. To avoid expensive and complex low cycle fatigue (LCF) tests for determining the combined hardening model parameter values for structural steel, empirical equations were proposed for each of the combined hardening model parameters based on the LCF test data of 21 steel grades collected from this study. In these equations, only the properties obtained from the monotonic tensile tests are required as input variables.