Huntington씨 병이 의심되는 2례

이현섭,백성욱,김상욱 대한신경과학회 1988 대한신경과학회지 Vol.6 No.2

Mathematical Modeling of Material Removal Rate in Roll- Type Linear CMP (Roll-CMP) Process: Effect of Polishing Pad

이현섭 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.4

Recently, a roll-type linear chemical mechanical polishing (Roll-CMP) process was developed for fabricating large flexible substrates such as flexible printed circuit boards (FPCBs). The major difference between the Roll-CMP and the conventional CMP is the type of contact between the polishing pad and the substrate. Roll-CMP uses line contact for material removal of the Cu film on FPCBs. Many researchers have studied mathematical models to understand the conventional CMP process. In this paper, a mathematical model on the material removal rate (MRR) of Roll-CMP is proposed based on Hertzian contact theory and previously studied models on conventional CMP to understand the effect of the polishing pad. Two kinds of polishing pads were prepared to investigate their effect on the material removal of copper clad laminate (CCL). The increase in the average radius of pad asperities over the standard deviation of pad asperities increases MRR. The slurry loading capacity of the polishing pad impacts the MRR of Cu as well. The proposed model may offer a theoretical understanding for the Roll-CMP process.

Temperature Distribution in Polishing Pad during CMP Process: Effect of Retaining Ring

이현섭,구영창,정해도 한국정밀공학회 2012 International Journal of Precision Engineering and Vol.13 No.1

Heat generation is inevitable during the chemical mechanical planarization (CMP) process because the mechanical and chemical removal of material is carried out by using abrasives and chemicals in the CMP slurry. In this paper, results obtained from experiments performed on a membrane-type carrier having a retaining ring were used to study the temperature distribution in a polishing pad during the CMP process. To understand and predict the distribution of temperature rise, a kinematical analysis of the temperature distribution was performed by considering the frictional characteristics of the process. The results of this study can be used to predict the temperature distribution in a polishing pad, and such predictions can help in developing a more effective CMP process.

특허 데이터 및 토픽 모델링을 활용한 CCUS 기술동향 분석

이현섭,서원철,이운식 대한산업공학회 2022 대한산업공학회 춘계학술대회논문집 Vol.2022 No.6

화학기계적 연마(CMP) 공정에서의 트라이볼로지 연구 동향

이현섭 한국트라이볼로지학회 2018 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.34 No.3

Chemical mechanical polishing (CMP) is a hybrid processing method in which the surface of a wafer is planarized by chemical and mechanical material removal. Since mechanical material removal in CMP is caused by the rolling or sliding of abrasive particles, interfacial friction during processing greatly influences the CMP results. In this paper, the trend of tribology research on CMP process is discussed. First, various friction force monitoring methods are introduced, and three elements in the CMP tribo-system are defined based on the material removal mechanism of the CMP process. Tribological studies on the CMP process include studies of interfacial friction due to changes in consumables such as slurry and polishing pad, modeling of material removal rate using contact mechanics, and stick-slip friction and scratches. The real area of contact (RCA) between the polishing pad and wafer also has a significant influence on the polishing result in the CMP process, and many researchers have studied RCA control and prediction. Despite the fact that the CMP process is a hybrid process using chemical reactions and mechanical material removal, tribological studies to date have yet to clarify the effects of chemical reactions on interfacial friction. In addition, it is necessary to clarify the relationship between the interface friction phenomenon and physical surface defects in CMP, and the cause of their occurrence.

Evaluation of environmental impacts during chemical mechanical polishing (CMP) for sustainable manufacturing

이현섭,Sunjoon Park,정해도 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.2

Reducing energy consumption has become a critical issue in manufacturing. The semiconductor industry in particular is confronted with environmental regulations on pollution associated with electric energy, chemical, and ultrapure water (UPW) consumptions. This paper presents the results of an evaluation of the environmental impacts during chemical mechanical polishing (CMP), a key process for planarization of dielectrics and metal films in ultra-large-scale integrated circuits. The steps in the CMP process are idling, conditioning, wetting, wafer loading/unloading, head dropping, polishing, and rinsing. The electric energy, CMP slurry, and UPW consumptions associated with the process and their impacts on global warming are evaluated from an environmental standpoint. The estimates of electric energy, slurry, and UPW consumptions as well as the associated greenhouse gas emissions presented in this paper will provide a technical aid for reducing the environmental burden associated with electricity consumption during the CMP process.

Mechanical Aspects of the Chemical Mechanical Polishing Process: A Review

이현섭,이다솔,정해도 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.4

Chemical mechanical polishing (CMP) is an essential semiconductor manufacturing process because of its local and global planarization ability in fabricating highly integrated devices. The CMP process uses both chemical reaction and mechanical polishing simultaneously. The combination of chemical reaction and mechanical removal in CMP is so complex that understanding the material removal mechanism has been a challenge for researchers and engineers. The chemical reaction mechanism is determined by the chemical composition of the CMP slurry and the material property of the target material. However, the mechanical action is a complex result of various mechanical factors of the process parameters and consumables. The mechanical material removal is a cornerstone of understanding and predicting CMP results. This review focuses on the mechanical aspects in CMP in terms of the process parameters and consumables of the CMP process that directly influence the material removal characteristics.

NAND 플래시 메모리용 B+트리의 인덱스 버퍼를 위한 효율적인 고장회복 관리기법

이현섭,김보경,주영도,이동호 한국정보과학회 2011 데이타베이스 연구 Vol.27 No.3

최근 NAND 플래시 메모리는 빠른 속도와 저 전력 소비라는 특징 때문에 차세대 저장장치의 소재로써 주목 받고 있다. 따라서 오늘날 다양한 저장 장치의 저장 매체가 하드디스크에서 플래시 메모리 기반의 SSD(solid state disk)로 대체되고 있다. 그러나 SSD는 플래시 메모리의 쓰기 전 소거 구조(erase-before-write architecture)와 비대칭 읽기 쓰기 연산 속도의 특성을 가지고 있기 때문에, 같은 지역에 집중적인 쓰기 연산을 발생하는 B트리를 구축하는 것은 많은 비용을 야기 할 것이다. 따라서 B트리 구축의 비용을 줄이기 위해 색인 버퍼를 이용한 방법들이 제안되어 왔다. 그러나 이러한 방법들은 전원 차단 시 버퍼에 유지되어 있던 색인 데이터를 유실하기 때문에 고장 회복의 문제를 가지고 있다. 이러한 문제를 해결하기 위해 본 논문에서는 NAND 플래시 메모리용 B트리의 인덱스 버퍼를 위한 효율적인 고장회복 관리 기법을 소개한다. 본 논문에서 제안하는 기법은 루트노드의 데이터가 갱신될 때 마다 검사점(checkpoint)을 두고 버퍼의 모든 색인 데이터들을 SSD로 커밋(commit)하기 때문에 고장 시점으로부터 마지막 커밋 시점으로 복구할 수 있다. 또한 본 알고리즘에 그림자 페이징(shadow paging) 정책을 적용하여 커밋 연산을 할 때 제자리갱신(overwrite)연산의 횟수를 줄였다. 이 방법은 복구를 할 때 쓰기 연산의 횟수를 줄여주기 때문에 고장회복의 속도를 향상시킬 수 있다. 결과적으로 제안하는 알고리즘은 SSD상에서 B트리를 구축할 때 작은 오버헤드로 안정적인 B트리를 구축 할 수 있을 뿐만 아니라 고장 회복을 위한 복구 시간을 줄였다. 또한 다양한 실험을 통하여 본 기법이 기존에 제안되었던 기법보다 SSD 상에서 좋은 성능을 보이는 것을 증명한다. Recently, NAND flash memory has been remarked as a best medium of the next generation storage because of its fast speed and low power consumption. Therefore, in various computing systems, the HDD (hard disk drive) has been replaced by the SSD (NAND flash-based solid state disk). However, since the SSD inherits the limitations of NAND flash memory such as erase-before-write architecture and asymmetric read/write speeds, it may result in severe performance degradation when building a B-tree that causes intensive writes at the same location. To reduce the cost of a B-tree implementation, several methods exploiting the buffer have been proposed so far. However, they have the recovery problem because all index data in the buffer are eliminated when power-failure occurs. In this paper, we introduce an efficient recovery management scheme for an index buffer of B-tree based on NAND flash memory for solving the recovery problem. Since the proposed method flushes all index data in the buffer into the SSD and creates the checkpoint whenever updating the root node, it can always recover the index structure into the last commit time. Also, it adopts the shadow-paging strategy for reducing the number of overwrites when committing the node. This method may reduce the time of recovery because it can eliminate a number of writes during the recovery. Consequently, it can efficiently reduce not only the consumed time but also the time of recovery when constructing a B-tree on SSD. We also show that our proposed algorithm yields a good performance on the SSD by comparing it to the related technique through various experiments.

매칭 모듈을 이용한 이동 객체와 VR 영상의 동기화

이현섭,유은재,김진덕,Lee, Hyoun-Sup,You, Eun-Jae,Kim, Jin-deog 한국정보통신학회 2017 한국정보통신학회논문지 Vol.21 No.7

최근 Virtual Reality(VR)와 Augmented Reality(AR)가 ICT분야에서 관심분야로 떠오르고 있다. 가상에서 실제와 같은 현실감을 느끼고 그 매력에 많은 사람들이 찾고 있다. 하지만 VR 이미지와 이동 객체의 움직임이 정확하게 들어맞지 않아 멀미를 느끼는 문제점도 발생하고 있다. 이와 같은 문제점을 해소할 수 있는 방안으로 VR 시스템의 어트랙션 적용이 있다. 본 논문에서는 VR 영상과 이동하는 객체의 움직임을 동기화하여 지연시간을 최소화할 수 있는 모듈을 제안한다. 제안하는 모듈은 VR 기기를 통하여 사용자가 바라보는 방향과 가속도 센서를 이용하여 이동 거리를 산출한다. 이 논문에서 제안하는 모듈은 어트랙션의 움직임이 고정된 경로를 따라 움직인다는 점을 주목하여 정확한 이동거리를 계산할 수 있을 것으로 사료된다. Recently, VR and AR are emerging as an area of interest in ICT. In virtual reality to feel like a real, many people are looking for them because of its charm. However, the motion of the VR image and the moving object are not synchronized exactly, and a problem of feeling nausea is also occurring. The problem should be solved by the application of Attraction in the VR system. In this paper, we propose a module that minimizes delay time by synchronizing movement of VR image and moving object. The proposed module calculates the moving distance using the direction and the acceleration sensor that the user views through the VR device. The module proposed in this paper will pay attention to the fact that the movement of the attraction moves along a fixed path, so that the accurate travel distance can be calculated.

전해이온화 슬러리 CMP 에서 과산수소 함량 변화에 따른 전기화학적 특성 분석

이현섭,조예진,김용훈,남영현 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.5