구리 무전해 도금의 반도체 구리 다마신 공정에의 적용을 위한 OCP 측정과 QCM을 통한 구리 무전해 도금 메커니즘 연구

학위논문 (박사)-- 서울대학교 대학원 : 화학생물공학부, 2013. 2. 김재정.Semiconductor process has been dramatically developed by introducing Cu damascene process, which enables the replacement of Al to Cu as interconnection material. The development continues to improve the performance of devices, and it is achieved by scaling up of chip integration so far. However, recently, the reduction of Cu line width according to the integration makes it difficult to deposit both diffusion barrier and seed layer uniformly inside of narrow trenches and vias using conventional physical vapor deposition. Thus, alternative deposition methods are suggested to solve the problem, such as atomic layer deposition and electroless deposition. Cu electroless deposition attracts a lot of attention for the use of the next generation metallization method because the direct deposition is possible on both the conventional diffusion barriers and the next generation diffusion barriers such as Ru-alloy or Co-ally. In this study, the electrochemical real-time observation method for the Cu electroless deposition was designed: both the open-circuit potential and mass change of an electrode were measured simultaneously during the deposition. Using the method, the Cu electroless deposition could be investigated in detail, such as the mechanism of Cu electroless deposition and the adsorption behaviors of organic additives. Based on the study, the electroless bottom-up filling of sub-60 nm trenches was finally achieved, confirming the possibility that the Cu electroless deposition could be used for the next generation metallization method. In the investigation of Cu electroless deposition, the effect of each component in the electroless bath on Cu surface was understood preferentially. It was observed that the Cu was continuously oxidized in the alkaline bath. However, when ethylenediaminetetraacetic acid, a well-known complexing agent, was in the solution together, it was found to participate in the removal of Cu oxides formed on the surface as well as the complexation of Cu ions in the solution. Formaldehyde, a reducing agent, was adsorbed onto the Cu surface and inhibited further Cu oxidation. Both components maintained low oxygen content on the Cu surface in the alkaline solution. During the Cu electroless deposition process, the induction period was observed at the initial stage of the deposition and it was related with the time that the formaldehyde was adsorbed and became activated on the surface, indicating that the oxidation of formaldehyde was the rate-determining step. The effect of Cu oxides on the electroless Cu film was also investigated. It was revealed that the formaldehyde rarely adsorbed on the oxidized Cu surface unless the ethylenediaminetetraacetic acid removed the oxide by the complexation. The same phenomenon was observed in the real electroless deposition. The pre-formed Cu oxide caused the rough surface of electrolessly deposited film, resulting from the irregular adsorption of formaldehyde. The effect of additive was investigated by injecting additives during the deposition. Additives were polyethylene glycol (PEG), 2,2-dipyridyl, and 3-N,N-dimethylaminodithiocarbamoyl-1-propanesulfonic acid (DPS). The addition of PEG during the deposition caused the reduction of the deposition rate as the PEG was gradually adsorbed on the surface. It was revealed that the adsorption of PEG blocked active sites for the formaldehyde adsorption, resulting in the suppression effect. The adsorption kinetics of PEG was strongly dependent on the diffusion coefficient of PEG, which was directly related to the molecular weight. It followed the adsorption-controlled kinetics when the diffusion coefficient was high, whereas that of PEG with low diffusion coefficient showed the diffusion-controlled kinetics. The strength of the suppression effect was also affected by the molecular weight of PEG: increasing the molecular weight enhanced the suppression effect. The adsorption behaviors of 2,2-dipyridyl and DPS were also studied. 2,2-dipyridyl was found to adsorb on the surface fast and reduce the deposition rate immediately. DPS was also adsorbed, accelerating or inhibiting the deposition according to its concentration. It was revealed that the suppression effect was enhanced when both 2,2-dipyridyl and DPS were added together. The electroless filling was then performed on sub-60 nm trenches by using the suppression enhancement. The simple concentration optimization of two additives achieved the bottom-up filling.Abstract i Contents iv List of Tables vii List of Figures viii Chapter I. Introduction 1 1.1. Metallization in ULSI technology 1 1.1.1. Cu damascene process 1 1.1.2. Cu deposition 4 1.1.3. Issues in present metallization process and Cu ELD 6 1.2. ELD 17 1.2.1. Basics of ELD 17 1.2.2. Mechanism of Cu ELD 20 1.2.3. Organic additives in Cu ELD bath 22 1.3. Observation of Cu ELD 31 1.3.1. Analysis tools for Cu ELD 31 1.3.2. Real-time observation of Cu ELD by OCP measurement with QCM 32 Chapter II. Experimental 35 2.1. Electrochemical analysis 35 2.1.1. OCP measurement with QCM 35 2.1.2. Coulometric reduction method 36 2.2. Film analysis 38 2.2.1. Preparation of Cu ELD films 38 2.2.2. Analysis tools 39 Chapter III. Investigation of Cu ELD mechanism 40 3.1. Role of each chemical component in Cu ELD bath 40 3.1.1. Adsorption of each chemical component and its effect on Cu surface 40 3.1.2. Cu ELD on Cu surface 46 3.2. Effect of Cu oxide on Cu ELD 58 3.2.1. Adsorption of HCHO on oxidized Cu surface 58 3.2.2. Cu ELD on oxidized Cu surface 60 3.3. Summary 70 Chapter IV. Effect of organic additives on Cu ELD 71 4.1. PEG 71 4.1.1. Adsorption behavior of PEG during Cu ELD 71 4.1.2. Surface morphology of electroless Cu film with PEG 79 4.1.3. Gap-filling with PEG 80 4.2. Combination of 2,2-dipyridyl and DPS 95 4.2.1. Adsorption behavior of 2,2-dipyridyl 95 4.2.2. Adsorption behavior of DPS 96 4.2.3. Synergetic effect of 2,2-dipyridyl and DPS 97 4.2.4. Gap-filling of sub-60 nm trenches 99 4.3. Summary 111 V. Conclusion 113 References 116 국문초록 125 Appendix I 128 Appendix II 158Docto

Prognosis of patients excluded by the definition of septic shock based on their lactate levels after initial fluid resuscitation: a prospective multi-center observational study

Background: Septic shock can be defined both by the presence of hyperlactatemia and need of vasopressors. Lactate levels should be measured after volume resuscitation (as per the Sepsis-3 definition). However, currently, no studies have evaluated patients who have been excluded by the new criteria for septic shock. The aim of this study was to determine the clinical characteristics and prognosis of these patients, based on their lactate levels after initial fluid resuscitation. Methods: This observational study was performed using a prospective, multi-center registry of septic shock, with the participation of 10 hospitals in the Korean Shock Society, between October 2015 and February 2017. We compared the 28-day mortality between patients who were excluded from the new definition (defined as lactate level <2 mmol/L after volume resuscitation) and those who were not (>= 2 mmol/L after volume resuscitation), from among a cohort of patients with refractory hypotension, and requiring the use of vasopressors. Other outcome variables such as in-hospital mortality, intensive care unit (ICU) stay (days), Sequential Organ Failure Assessment (SOFA) scores and Acute Physiology and Chronic Health Evaluation (APACHE) II scores were also analyzed. Results: Of 567 patients with refractory hypotension, requiring the use of vasopressors, 435 had elevated lactate levels, while 83 did not have elevated lactate levels (either initially or after volume resuscitation), and 49 (8.2%) had elevated lactate levels initially, which normalized after fluid resuscitation. Thus, these 49 patients were excluded by the new definition of septic shock. These patients, in whom perfusion was restored, demonstrated significantly lower age, platelet count, and initial and subsequent lactate levels (all p < 0.01). Similarly, significantly lower 28-day mortality was observed in these patients than in those who had not been excluded (8.2% vs 25.5%, p = 0.02). In-hospital mortality and the maximum SOFA score were also significantly lower in the excluded patients group (p = 0.03, both). Conclusions: It seems reasonable for septic shock to be defined by the lactate levels after volume resuscitation. However, owing to the small number of patients in whom lactate levels were improved, further study is warranted

Clinical outcome comparison of patients with septic shock defined by the new sepsis-3 criteria and by previous criteria

Background: We compared the clinical characteristics and outcomes between the new definition of sepsis-3 septic shock and the definition previously used from 1991 until recently. Methods: We conducted an observational study using a prospective, multi-center registry of septic shock from October 2015 to February 2017. Registry data were collected by 10 emergency departments (EDs) in tertiary hospitals that are members of the Korean Shock Society. Data on septic shock patients who met the previous septic shock definition were collected. The patients were divided into a sepsis-3 defined septic shock group, made up of those who met the new criteria for refractory hypotension with hyperlactatemia, and a group of those who met only the 1991 definition for septic shock. The primary outcome was 90-day mortality, and secondary outcomes were 28-day mortality and in-hospital mortality. Results: Of all 1,028 included patients, 574 (55.8%) met the septic shock criteria for sepsis-3, leaving 454 patients who met only the previous definition. Those who met the sepsis-3 criteria demonstrated higher comorbidity than those who met the previous definition (83.1% vs. 75.3%, P<0.01), but there was no difference in infection focus. The sequential organ failure assessment (SOFA) (initial/maximal), the acute physiology, and the chronic health evaluation II scores were significantly higher in for those who met the sepsis-3 criteria [6.5 +/- 3.1 vs. 5.0 +/- 2.9, 9.3 +/- 3.8 vs. 6.6 +/- 3.4, and 20.0 (15.0-26.0) vs. 15.0 (10.0-20.3), respectively; P<0.01]. The 90-day mortality was significantly higher in the sepsis-3 group (32.1% vs. 23.3%; P<0.01). In-hospital and 28-day mortality were also higher in the sepsis-3 group (26.8% vs. 17.1% and 25.1% vs. 16.5%, respectively; P<0.01). Conclusions: The new definition of septic shock successfully selected patients with greater severities and worse outcomes

Surface pretreatments for Cu electroless deposition and its monitoring by electrochemical method

학위논문(석사) --서울대학교 대학원 :화학생물공학부, 2009.2.Maste

Impacts of Changes in Intergovernmental Grants Policy on the Efficiency and Equity of Local Government Financial Management

본 연구는 정부 간 재정지원 제도의 변화가 지방정부의 효율성과 형평성에 미치는 영향을 분석하였다. 정책학, 행정학 및 경제학 연구에서 효율성과 형평성은 기본적으로 상충 관계로 받아들여짐에도 불구하고 정의 상관관계의 가능성에 대한 이론적 정책적 논의가 지속되고 있다. 본 연구에서는 미국 특별지방정부 중 하나인 학교구를 대상으로 뉴저지 주의 교육재정제도의 변화가 효율성과 형평성에 미치는 영향을 분석하여 양자 간의 관계에 대한 실증 분석 결과를 제공하고자 한다. 분석 결과, 뉴저지 주의 지방 간 재정지원 제도의 변화는 학교구의 효율성과 형평성에 모두 부정적인 영향을 미치는 것으로 나타났다. 이러한 결과는 재정지원 제도의 변화가 학교구의 공공선택론적, 관리적 유인의 변화를 유도하여 행태변화, 즉, 즉, 제산세율 조정, 예산 결정 및 재정 운영 등의 변화를 가져올 수 있다는 점을 시사하고 있다. This study attempts to analyze the impact of changes in the intergovernmental transfer system on local government equity and efficiency. Even though efficiency and equity have been regarded as trade-offs in the fields of public policy, public administration, and economics, the search for a possible positive relationship has continued. Taking advantage of the quasi-experimental research opportunity of New Jersey's educational finance reform, the impact of the institutional changes on equity and efficiency are analyzed. The results reveal that the institutional changes have detrimental impacts on both the equity and efficiency of school districts. It implies that the institutional changes are more likely to affect the public choice and managerial incentives of school districts and thereby induced changes in property tax rates, education budget reallocation, and financial management.이 논문은 2008년도 정부재원(교육과학기술부 인문사회연구역량강화사업비)으로 한국연구재단의 지원을 받아 연구되었음(NRF-2008-332-B00549 (I00967))