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Analysis of Random Variations and Variation-Robust Advanced Device Structures
Nam, Hyohyun,Lee, Gyo Sub,Lee, Hyunjae,Park, In Jun,Shin, Changhwan The Institute of Electronics and Information Engin 2014 Journal of semiconductor technology and science Vol.14 No.1
In the past few decades, CMOS logic technologies and devices have been successfully developed with the steady miniaturization of the feature size. At the sub-30-nm CMOS technology nodes, one of the main hurdles for continuously and successfully scaling down CMOS devices is the parametric failure caused by random variations such as line edge roughness (LER), random dopant fluctuation (RDF), and work-function variation (WFV). The characteristics of each random variation source and its effect on advanced device structures such as multigate and ultra-thin-body devices (vs. conventional planar bulk MOSFET) are discussed in detail. Further, suggested are suppression methods for the LER-, RDF-, and WFV-induced threshold voltage (VTH) variations in advanced CMOS logic technologies including the double-patterning and double-etching (2P2E) technique and in advanced device structures including the fully depleted silicon-on-insulator (FD-SOI) MOSFET and FinFET/tri-gate MOSFET at the sub-30-nm nodes. The segmented-channel MOSFET (SegFET) and junctionless transistor (JLT) that can suppress the random variations and the SegFET-/JLT-based static random access memory (SRAM) cell that enhance the read and write margins at a time, though generally with a trade-off between the read and the write margins, are introduced.
Analysis of Random Variations and Variation-Robust Advanced Device Structures
Hyohyun Nam,Gyo Sub Lee,Hyunjae Lee,In Jun Park,Changhwan Shin 대한전자공학회 2014 Journal of semiconductor technology and science Vol.14 No.1
In the past few decades, CMOS logic technologies and devices have been successfully developed with the steady miniaturization of the feature size. At the sub-30-nm CMOS technology nodes, one of the main hurdles for continuously and successfully scaling down CMOS devices is the parametric failure caused by random variations such as line edge roughness (LER), random dopant fluctuation (RDF), and work-function variation (WFV). The characteristics of each random variation source and its effect on advanced device structures such as multigate and ultra-thin-body devices (vs. conventional planar bulk MOSFET) are discussed in detail. Further, suggested are suppression methods for the LER-, RDF-, and WFV-induced threshold voltage (VTH) variations in advanced CMOS logic technologies including the double-patterning and double-etching (2P2E) technique and in advanced device structures including the fully depleted siliconon-insulator (FD-SOI) MOSFET and FinFET/tri-gate MOSFET at the sub-30-nm nodes. The segmentedchannel MOSFET (SegFET) and junctionless transistor (JLT) that can suppress the random variations and the SegFET-/JLT-based static random access memory (SRAM) cell that enhance the read and write margins at a time, though generally with a trade-off between the read and the write margins, are introduced.
Lee, Gyo Sub,Shin, Changhwan The Institute of Electronics and Information Engin 2014 Journal of semiconductor technology and science Vol.14 No.1
In high-${\kappa}$/metal-gate (HK/MG) metal-oxide-semiconductor field-effect transistors (MOSFETs) at 45-nm and below, the metal-gate material consists of a number of grains with different grain orientations. Thus, Monte Carlo (MC) simulation of the threshold voltage ($V_{TH}$) variation caused by the workfunction variation (WFV) using a limited number of samples (i.e., approximately a few hundreds of samples) would be misleading. It is ideal to run the MC simulation using a statistically significant number of samples (>~$10^6$); however, it is expensive in terms of the computing requirement for reasonably estimating the WFV-induced $V_{TH}$ variation in the HK/MG MOSFETs. In this work, a simple matrix model is suggested to implement a computing-inexpensive approach to estimate the WFV-induced $V_{TH}$ variation. The suggested model has been verified by experimental data, and the amount of WFV-induced $V_{TH}$ variation, as well as the $V_{TH}$ lowering is revealed.
Worst Case Sampling Method to Estimate the Impact of Random Variation on Static Random Access Memory
Gyo Sub Lee,Changhwan Shin Institute of Electrical and Electronics Engineers 2015 IEEE transactions on electron devices Vol. No.
<P>We propose a worst case sampling method for quantitatively estimating the impact of random variation on static random access memory (SRAM) cells. This method enables us to predict the values of SRAM read/write metrics beyond the Six Sigma regime. First, we developed a compact model with a Monte Carlo simulation. The model includes both device modeling and sample size extension to predict and quickly estimate SRAM read/write metrics accurately. We verified the accuracy of the model by comparing the simulation results to previously published silicon data. Our results provide circuit designers with insight into the impact of random variations on SRAM cells. In particular, we demonstrate how SRAM cell operations can be protected from harsh random variations using word-line voltage margins as the key parameter.</P>
Gyo Sub Lee,Changhwan Shin 대한전자공학회 2014 Journal of semiconductor technology and science Vol.14 No.1
In high-κ/metal-gate (HK/MG) metaloxide-semiconductor field-effect transistors (MOSFETs) at 45-nm and below, the metal-gate material consists of a number of grains with different grain orientations. Thus, Monte Carlo (MC) simulation of the threshold voltage (VTH) variation caused by the workfunction variation (WFV) using a limited number of samples (i.e., approximately a few hundreds of samples) would be misleading. It is ideal to run the MC simulation using a statistically significant number of samples (> ~ 106); however, it is expensive in terms of the computing requirement for reasonably estimating the WFV-induced VTH variation in the HK/MG MOSFETs. In this work, a simple matrix model is suggested to implement a computing-inexpensive approach to estimate the WFV-induced VTH variation. The suggested model has been verified by experimental data, and the amount of WFV-induced VTH variation, as well as the VTH lowering is revealed.
Kang, Gyung-Don,Lee, Ki-Hoon,Do, Sun-Gil,Kim, Chung-Sub,Suh, Jun-Gyo,Oh, Yang-Seok,Nahm, Joong-Hee Korean Society of Sericultural Science 2001 International Journal of Industrial Entomology Vol.2 No.1
Silk fibroin (SF) derided from the domestic silk worm, bombyx mori, is the natural protein and widely used as bio-functional materials as well as apparels. We studied the livers protective effect of SF from alcohol-induced hepatotoxicity in the alcohol preference mouse. To increase more absorption of SF in experimental animals, molecular weight of SF was lowered by 2N of HCI aqueous solution at 10$0^{\circ}C$ for 48 hrs. SF was added to liquid diet with alcohol and fed to the alcohol preference mice for 4 weeks. To assess the liver function, the concentration of alanine aminotransferase (AlT), aspartate aminotransferase (AST) and cholesterol present in either blood or liver tissue were measured. As compared with non-SF treated groups the SF-treated showed significantly low concentrations of ALT, AST, cholesterol and triacylglycerol values, respectively. Histopathological examination revealed that the extent of hepatocyte injury in the SF-treated group was reduced when it was compared with non SF-treated group. These results suggest that SF may have liver protective effects against alcohol-induced hepatotoxicity.
Oh, Sangheon,Jo, Jaesung,Lee, Hyunjae,Lee, Gyo Sub,Park, Jung-Dong,Shin, Changhwan The Institute of Electronics and Information Engin 2015 Journal of semiconductor technology and science Vol.15 No.3
As semiconductor devices are being scaled down, random variation becomes a critical issue, especially in the case of static random access memory (SRAM). Thus, there is an urgent need for statistical methodologies to analyze the impact of random variations on the SRAM. In this paper, we propose a novel sampling method based on the concept of a confidence ellipse. Results show that the proposed method estimates the SRAM margin metrics in high-sigma regimes more efficiently than the standard Monte Carlo (MC) method.
방사된 이후 번식쌍을 형성한 따오기의 행동권에 따른 서식환경 특성
조봉교 ( Soo-dong Lee ),이수동 ( Bong-gyo Cho ),오충현 ( Chung-hyeon Oh ),진민화 ( Min-hwa Jin ),한영섭 ( Young-sub Han ),김성진 ( Seong-jin Kim ) 한국환경생태학회 2021 한국환경생태학회 학술대회지 Vol.2021 No.1
섭금류인 따오기는 국제자연보전연맹(IUCN) 적색목록(red data book)에 등재되어 있으며(BirdLife International 2000), 국내에서는 멸종위기야생생물Ⅱ 및 천연기념물 제198호로 지정되어 있다. 19세기 중반까지 한반도를 비롯하여 일본, 중국, 러시아 등에 널리 분포하였으나(Li and Li, 1998; Ding, 2004), 1930년대 이후 수렵과 농약 및 화학비료 사용, 서식지 파괴 등으로 한반도와 일본의 야생에서는 멸종된 것으로 밝혀졌다(한 2007; 강 등 2008). 중국에서도 멸종 직전이었으나 1981년 야생에 남아 있던 7개체를 토대로 인공증식과 서식지 복원을 통하여 2,000여 개체까지 증가하였다(Liu et al., 2014). 일본과 한국의 경우에도 야생에서 멸종한 후 중국에서 기증받아 재도입 개체군을 확립하여 위기에 처한 종을 보존하는 성공적인 모델로 간주되고 있다(Liu 2014). 우리나라에서는 1979년 판문점에서 1개체가 관찰된 이후 발견되지 않았으나, 2008년도에 따오기 한 쌍을 중국에서 들여온 후 2019년 5월에 1차, 2020년 5월에 2차 야생 방사를 실시하였다(우포따 오기과 2020). 이와 같이 멸종위기에 처한 생물종 복원은 전지구적인 과제인데 중국, 일본, 국내에서 따오기 증식 기술, 서식 환경에 대한 연구가 지속되고 있는데 방사한 개체의 번식과 관련해서도 행동권, 서식처 이용 패턴 등에 대해 꾸준한 연구가 필요하여 진행하였다. 본 연구는 우포따오기복원센터에서 1차(2019.5.22.), 2차(2020.5.28.)에 걸쳐 야생에 방사된 따오기 중 번식쌍을 이룬 개체의 생육환경을 파악하고자 진행하였다. 2번의 방사 개체 중 1차 때 방사한 개체가 번식쌍을 형성하여 2회의 둥지를 조성하였으나 유조를 키워내는 것은 실패하였다. 각각의 개체는 위성추적장치를 부착하여 9회/1일의 좌표를 수신하였고 QGIS를 활용하여 행동권, 이동현황, 이용 지역 서식환경 특성을 분석하였다. 번식 따오기는 1차 둥지(2020. 4. 3.~2020. 5. 1.)를 활용하여 산란하였으나 실패한 후 2차 둥지(2020. 5. 21.~ 2020. 6. 21.)를 시도한 것이 확인되었다. 1차 및 2차 둥지 조성 지역의 지형을 살펴보면, 해발고는 25~50m와 50~75m, 향은 남향과 북서향이었다. 쌍을 이뤄 번식하는 따오기는 산림 주연부에 둥지를 짓고 전면에 입지한 논, 밭, 경작지 또는 복원센터에서 먹이를 섭취하는 것으로 분석되었다. 결과적으로 따오기는 둥지의 입지를 먹이터와 안정적인 휴식터가 접하는 장소에 선정하는 것으로 판단되었다. 번식 개체의 이동은 쌍을 이루기 전에는 복원센터를 중심으로 주변을 돌아다녔으나 이후에는 둥지를 중심으로 또는 먹이를 구하기 위해 복원센터를 왕복하는 패턴이었다. 행동권을 분석한 결과 1차 둥지 시기에는 소나무림을 휴식처로, 마을 전면에 조성한 논, 밭, 묘지 등을 주요 먹이터로 활용하였다. 특이한 점은 약 2.5㎞ 떨어진 복원센터를 핵심적인 먹이터로 활용하였다. 2차 둥지는 1차 둥지 맞은편에 지었는데, 주변 산림을 휴식처로, 논, 밭, 묘지 등을 주요 먹이터로, 복원센터를 핵심적인 먹이터로 활용한 것은 1차 둥지 시기와 유사한 패턴이었다. 먹이가 부족하거나 휴식이 필요할 때는 여전히 최초 방사지를 이용하는 것으로 분석되었다. 다만, 1차 둥지 때와는 달리 2차 둥지 시기에는 둥지 주변에 지속적으로 머물었으며, 복원센터를 방문한 횟수도 줄어들었다. 2번의 둥지는 모두 소나무에 조성하였는데, 1차는 가지 끝에, 2차에서는 주간에 조성하여 후자의 안정성이 더 높았던 것을 확인할 수 있었다. 둥지의 재료는 가까운 곳에서 구할 수 있는 재료를 활용하였는데 소나무 가지와 솔잎의 비율이 가장 높았고 그 외에는 대추나무, 헛개나무 등 전정된 가지를 이용한 것으로 나타났다.