• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.239-240
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• 2008

As semiconductor devices are scaled down for better performance and more functionality, the Cu-based interconnects suffer from the increase of the resistivity of the Cu wires. The resistivity increase, which is attributed to the electron scattering from grain boundaries and interfaces, needs to be addressed in order to further scale down semiconductor devices [1]. The increase in the resistivity of the interconnect can be alleviated by increasing the grain size of electroplating (EP)-Cu or by modifying the Cu surface [1]. Another possible solution is to maximize the portion of the EP-Cu volume in the vias or damascene structures with the conformal diffusion barrier and seed layer by optimizing their deposition processes during Cu interconnect fabrication, which are currently ionized physical vapor deposition (IPVD)-based Ta/TaN bilayer and IPVD-Cu, respectively. The use of in-situ etching, during IPVD of the barrier or the seed layer, has been effective in enlarging the trench volume where the Cu is filled, resulting in improved reliability and performance of the Cu-based interconnect. However, the application of IPVD technology is expected to be limited eventually because of poor sidewall step coverage and the narrow top part of the damascene structures. Recently, Ru has been suggested as a diffusion barrier that is compatible with the direct plating of Cu [2-3]. A single-layer diffusion barrier for the direct plating of Cu is desirable to optimize the resistance of the Cu interconnects because it eliminates the Cu-seed layer. However, previous studies have shown that the Ru by itself is not a suitable diffusion barrier for Cu metallization [4-6]. Thus, the diffusion barrier performance of the Ru film should be improved in order for it to be successfully incorporated as a seed layer/barrier layer for the direct plating of Cu. The improvement of its barrier performance, by modifying the Ru microstructure from columnar to amorphous (by incorporating the N into Ru during PVD), has been previously reported [7]. Another approach for improving the barrier performance of the Ru film is to use Ru as a just seed layer and combine it with superior materials to function as a diffusion barrier against the Cu. A RulTaN bilayer prepared by PVD has recently been suggested as a seed layer/diffusion barrier for Cu. This bilayer was stable between the Cu and Si after annealing at $700^{\circ}C$ for I min [8]. Although these reports dealt with the possible applications of Ru for Cu metallization, cases where the Ru film was prepared by atomic layer deposition (ALD) have not been identified. These are important because of ALD's excellent conformality. In this study, a bilayer diffusion barrier of Ru/TaCN prepared by ALD was investigated. As the addition of the third element into the transition metal nitride disrupts the crystal lattice and leads to the formation of a stable ternary amorphous material, as indicated by Nicolet [9], ALD-TaCN is expected to improve the diffusion barrier performance of the ALD-Ru against Cu. Ru was deposited by a sequential supply of bis(ethylcyclopentadienyl)ruthenium [Ru$(EtCp)_2$] and $NH_3$plasma and TaCN by a sequential supply of $(NEt_2)_3Ta=Nbu^t$ (tert-butylimido-trisdiethylamido-tantalum, TBTDET) and $H_2$ plasma. Sheet resistance measurements, X-ray diffractometry (XRD), and Auger electron spectroscopy (AES) analysis showed that the bilayer diffusion barriers of ALD-Ru (12 nm)/ALD-TaCN (2 nm) and ALD-Ru (4nm)/ALD-TaCN (2 nm) prevented the Cu diffusion up to annealing temperatures of 600 and $550^{\circ}C$ for 30 min, respectively. This is found to be due to the excellent diffusion barrier performance of the ALD-TaCN film against the Cu, due to it having an amorphous structure. A 5-nm-thick ALD-TaCN film was even stable up to annealing at $650^{\circ}C$ between Cu and Si. Transmission electron microscopy (TEM) investigation combined with energy dispersive spectroscopy (EDS) analysis revealed that the ALD-Ru/ALD-TaCN diffusion barrier failed by the Cu diffusion through the bilayer into the Si substrate. This is due to the ALD-TaCN interlayer preventing the interfacial reaction between the Ru and Si.

• 한국과학교육학회지
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• 제31권1호
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• pp.78-98
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• 2011

이 연구의 목적은 자료해석에 영향을 미치는 학습자 요인으로 인지양식에 주목하고 학습자의 인지양식에 따른 자료해석의 특성을 알아보고자 하는 것이다. 연구대상으로 통합탐구가 가능한 형식적 조작기에 접어드는 초등학교 6학년을 선택하였으며 인지양식 검사를 통해 전체적 인지양식과 분석적 인지양식으로 집단을 분류한 후 과학적 자료해석 과제를 투입하여 이들의 자료해석 활동을 촬영하고, 사후 면담을 실시하여 프로토콜을 생성하였으며, 피험자들이 작성한 자료해석 활동지도 분석에 사용하였다. 연구에 따른 결과를 보면, 첫째, 자료해석에서 학습자들은 자료해석의 초기 상태에서 중간 상태를 거쳐 목표 상태에 이르는 동안 다양한 조작자를 활용한다. 본 연구를 통해서는 자료 확인, 변인 인식, 불확실한 자료의 처리, 수학적 조작, 표지의 사용, 사전지식의 이용, 관계 분석, 패턴 분석, 예상이 분석되었다. 인지 양식에 따라 자료해석의 초기 상태에서 자료를 확인하는 양상에 차이가 있다. 둘째, 초등학생의 인지양식에 따라 자료해석의 방향성과 선호하는 자료의 형태가 특징적으로 나타났다. 전체적 인지양식의 학습자는 일반적인 원리나 과학적 문제에 대한 답을 도출한 후 자료를 통해 세부적인 정보를 분석하는 하향식 접근과 연역적 기술의 특성을 보이며, 분석적 인지양식의 학습자들은 자료의 전체적인 양상에 집중하기보다 제시된 자료의 연속적인 세부 항목과 절차에 따라 정보를 일차적으로 분석하여 기술해 나가는 일차적이고 연대기적 구조를 가진다. 또한 이러한 방식으로 분석해 낸 세부 정보를 바탕으로 귀납적인 방법으로 과학적 문제에 대한 답을 얻는 상향식 접근 방법을 주로 사용한다. 따라서 다양한 교수학습 상황에서 효과적인 학습을 위해서는 학습자들의 인지양식에 대한 이해를 바탕으로 이를 효과적으로 지원하는 교수 설계 전략을 고안하기 위해 노력해야 할 필요가 있다.