Electromechanical Switches Fabricated by Electrophoretic Deposition of Single Wall Carbon Nanotube Films

University of Minnesota Ph.D. dissertation.August 2015. Major: Electrical/Computer Engineering. Advisor: Stephen Campbell. 1 computer file (PDF); xi, 110 pages.Power dissipation is a critical problem of CMOS devices especially for mobile applications. Many efforts have been made to solve the problem, but there are still major issues associated with scaling the device size. Micro electromechanical (MEMS) and nano electromechanical (NEMS) devices are one candidate to solve the problems because of their excellent standby leakage. However, the switches have a tradeoff between low operating power and high device speed. Suspended beams with low mass density and good mechanical properties provide a way to optimize the device. Carbon nanotubes (CNTs) have the low mass density and excellent mechanical properties to enable high performance MEMS/NEMS devices. However, the high temperature required for the direct synthesis for CNTs makes it difficult for them to be compatible with a substrate containing transistors. Therefore, continuous film deposition techniques are investigated with low temperature (< 300 C). Electrophoretic deposition (EPD) is a simple and versatile processing method to deposit carbon nanotubes on the substrate at room temperature. The movement of the charged CNTs in suspension occurs by an applied electric field. The deposited CNT film thickness can be controlled through the applied voltage and process time. We demonstrate the use of an EPD process to deposit various thicknesses of CNT films. Film thicknesses are studied as a function of, deposition time, electric field strength, and suspension concentration. The deposition mechanism of the EPD process for carbon nanotube layers was explained with experimental data. We determined the film mass density and electrical/optical properties of SWCNT films. Rutherford backscattering spectroscopy was used to determine the film mass density. Films created in this manner had a mass density that varies with thickness from 0.12 to 0.54 g/cm3 and a resistivity of 2.1410-3 Ω∙cm. For the mechanical property measurements, we describe a technique to fabricate free-standing thin films using modified Langmuir-Blodgett method. Then we extracted the Young’s modulus of the film from the load-displacement data from nanoindentation using the appropriate modeling. The Young’s modulus had a range of 4.72 to 5.67 GPa, independent of deposited thickness. We fabricated two-terminal fixed beam switches with SWCNT thin films using the EPD process. Device pull-in voltages under 1V were achieved by decreasing the air-gap. The pull-in voltages were compared with the calculated results using the device geometry and extracted Young’s modulus from nanoindentation. Generally good agreement was observed. Also, we found a range of 2.4 to 3.5 MHz resonant frequency. However, we encountered several problems with the device including a gradual turn-on, hysteresis between pull-in and pull-out voltage, changes in the pull-in voltages with repeated on-off cycling, and early failure due to moisture absorption during testing in the air. Mechanisms for these observations are postulated. Further work is needed to improve device performance and reliability

다기능 AFM을 통한 고유전율 박막의 고급 계측 및 3차원 리소그래피를 위한 벌지 제거 연구

학위논문 (박사)-- 서울대학교 대학원 : 융합과학기술대학원 융합과학부(나노융합전공), 2019. 2. 김연상.Scanning probe microscopy (SPM) is widely used to analyze the surface structures and properties of semiconductor and bio-molecular films. The merits of the SPM method are that it does not require any process for sample preparation and minimizes damages of the probing sample. Moreover, the growth of industries related to semiconductor and nano-bio devices has led to the development of nanotechnology. Many researchers now become aware of the importance of local variations, such as the local doping profiles of semiconductors, the work function of two-dimensional materials, the surface profiles of bio-molecular films, the diodic behavior of nanofluidic devices, the surface roughness of semiconductor thin films, and the distribution of local surface charge. Thus, the researchers are seeking appropriate SPM equipment to analyze the local variations. In recent years, atomic force microscopes have emerged that can perform various functions. Especially, low-noise atomic force microscopy can be used to measure linewidths of nanoscale next-generation semiconductors or inspection for ultra-thin films. Therefore, Korea Research Institute of Standards and Science has developed a low noise atomic force microscope considering the industrial application. As well as, it has been developed to perform sophisticated nano/micro patterns by adding the function of nano-indentation. The low-noise atomic force microscope avoids the installation of an internal stage due to the nature of the development background. Although it contributes significantly to the signal integrity of the low-noise atomic force microscope, it serves as a weakness to limit the scan area of the test sample. Therefore, it is essential to have an independent external stage to compensate the weakness. In this paper, we have developed the middle range moving stage for the measurements of the standard reference samples. The maximum travel length of the external 4-axis stage is 10 mm. For image scanning of a specific area of interest, the sample is positioned with micron accuracy through an external stage and then finely positioned using a PI XY piezo scanner. We confirmed that the position error of the developed stage can be ignored by the reproducibility experiment. Subsequently, the sidewall of the improved vertical parallel structure (IVPS) was measured. The repeatability and reproducibility (R&R) of the CD measurement was estimated using the CDR30-EBD tip. Finally, we found that the tip wear was minimized by measuring the TGX1 sample with the undercut structure. Thus, the development of independent external stages can be useful for many tasks that require large scanning areas. In the industrial semiconductor fabrication, the inspection of thin films is performed through optical equipment to check the uniformity of wafers. In the next-generation semiconductor industry, high-capacity and low-power devices with complex lithography patterns and ultra-thin insulating films are emerging. Therefore, in order to improve the yield of semiconductor devices, it is necessary to inspect not only the thickness of these thin films but also local variations. Indeed, the surface roughness of the semiconductor process may affect the formation of the ultrathin film, and even if the process of the ultra-thin films is optimized by the atomic layer deposition (ALD), the performance of the device may be degraded due to the roughened surface. Therefore, atomic force microscopy is the most suitable method for quantifying the properties of thin films and for analyzing the local surface structures. In this thesis, critical roughness (CR) was defined for the first time in a nanoscale by devising a roughness scaling process as a method for managing hafnium oxide film, which is a high-k insulating film of a MOS transistor. The surface roughness of the substrate was processed by a wet etching method, and an ALD process was used to obtain a hafnium oxide film. This is a study on the influence of the roughness of the lower layer on the roughness of the upper layer, and this definition makes it possible to present the criteria of the standard production in the in-line oxide film process. Moreover, we confirmed that the CR value defined in this study was effective by realizing the MIM diode structures with different roughness. Furthermore, new research methods were introduced through the indentation lithography. The first study suggests that nano- and micro-patterns can be formed on biofilms that is impracticable by electron beam lithography. The indentation method can be a means to compensate the weaknesses of electron beam lithography. The second study is to selectively remove the bulges generated during the indentation process. For many years, it was a quite important issue because the formation of the bulge was a major factor impeding the development of indentation technology. All in all, in this thesis, various research themes realized by the multi-functional AFM are presented. The new definition of the roughness contributed to the in-line process control. The patterned biofilm could be used as a standard sample of the TOF-SIMS imaging. The selective removal of the bulges suggested a new method for three-dimensional nanolithography. Therefore, this research is expected to be a cost effective technology in the industry and to be used in various research fields.스캐닝 프루브 현미경 (SPM)은 반도체 및 생체 분자 필름의 표면 구조 및 특성을 분석하는 데 널리 사용된다. SPM 방법의 장점은 시료 준비를 위한 어떠한 공정도 필요로 하지 않으며 조사 시료의 손상을 최소화한다는 것이다. 또한, 반도체 및 나노 바이오 디바이스와 관련된 산업의 성장은 나노 기술의 발전으로 이어지고 있다. 그래서 많은 연구자들은 반도체의 국소 도핑 프로파일, 반도체 박막의 표면 거칠기, 2 차원 재료의 일 함수, 국소 표면 전하 분포, 유기-바이오 분자 박막, 나노 유체 장치의 표면 등을 분석하기위해 SPM 장비를 활용하고 있다. 최근에는 표면 분석 기능뿐만 아니라 여러가지 기능을 수행할 수 있는 원자력 현미경들이 등장하고 있다. 그 중에서도 저소음 원자력 현미경은 나노 스케일의 차세대 반도체 선폭을 측정하거나 초박막의 표면 검사에 이용될 수 있다. 따라서 산업적인 응용을 고려하여 한국표준과학연구원에서는 저소음 원자력 현미경을 개발하였고, 나노 인덴테이션 기능을 추가하여 R&D 수준에서 수십 나노의 정교한 패턴을 형성할 수 있는 공정 방법을 개발하고 있다. 저소음 원자력 현미경은 개발 배경의 특성상 내부적인 시료 이동 스테이지의 설치를 지양한다. 이는 저소음 원자력 현미경의 수취 신호 안정성에 크게 기여하는 최선의 선택이긴 하지만, 검사 시료의 측정 영역을 축소시키는 약점으로 작용하고 있다. 따라서 이를 보완할 수 있는 독립적인 외부 스테이지는 필수적이라고 할 수 있기때문에, 이 논문에서는 중거리 이동 스테이지 개발을 통해 기준 시료의 임계 치수를 측정 할 수 있도록 개발하였다. 외부 4 축 스테이지의 최대 이동 길이는 10 mm이며, 특정 대상 영역의 이미지 스캐닝의 경우, 샘플을 외부 스테이지를 통해 마이크론 정확도의 위치 지정을 거친 후, PI XY piezo 스캐너를 이용하여 미세 위치 설정을 한다. 개발된 스테이지의 위치 에러는 재현성 실험을 통해 무시할 수 있음을 확인하였다. 이어서, 개선된 수직 평행 구조(IVPS)의 측벽을 측정하고 CD 측정의 반복성 및 재현성을 CDR30-EBD 팁을 사용하여 추정하였다. 마지막으로, 돌출 구조로 된 TGX1 샘플을 측정하여 팁 마모를 최소화 할 수 있음을 확인했다. 따라서 독립적인 외부 스테이지의 개발은 향후 넓은 영역을 스캔해야하는 여러가지 임무에 유용하게 적용될 수 있다. 산업의 in-line 시스템에서는 대면적 웨이퍼의 균일도를 검사하기 위해 광학적인 측정장비를 통해 박막 검사를 수행한다. 하지만 최근 차세대 반도체 산업에서는 고용량 및 저전력 디바이스의 출현으로 리소그래피 패턴이 점점 복잡해지고 절연체 박막의 두께는 수 나노 미터에서 서브 나노 미터 범위로 축소되고 있다. 따라서 가까운 미래의 in-line 공정에서는 반도체 장치의 생산 수율 향상을 위해서, 이들 박막의 두께뿐만 아니라 3차원 (3D) 표면 정보를 검사하는 것이 필요해지고 있다. 실제 반도체 공정을 거친 표면의 거칠기는 향후 초박막 공정에 영향을 미치기도 하며, 표면이 거친 상태에서는 원자층 증착법(atomic layer deposition, ALD)에 의해 초박막 공정이 최적화되어 있다하더라도 소자에 영향을 줄 수 있기 때문이다. 따라서 박막의 성질을 정량화하고 국소적 표면 구조를 분석하기위해서는 원자력 현미경이 가장 적합한 분석법이라고 할 수 있다. 이 논문에서는 MOS 트렌지스터의 high-k 절연막인 하프늄 산화막 공정관리를 위한 방안으로 roughness scaling method를 고안하여 나노 스케일에서 최초로 임계거칠기(critical roughness, CR)을 정의하였다. 기판의 표면거칠기는 습식 식각 방식으로 진행하였으며, 하프늄 산화막을 얻기 위해 ALD 공정을 이용하였다. 이는 하부 층의 거칠기가 상부 층의 거칠기에 주는 영향성에 대한 연구이며, 이 정의를 통해 in-line 산화막 공정상에서 생산관리의 기준을 제시할 수 있게 되었다. 그리고 초박막 거칠기에 따른 MIM 다이오드 구조를 실현함으로써 이 연구에서 정의된 CR값이 실효성을 가짐을 확인하였다. 마지막으로 이 논문에서는 다기능성 원자현미경을 이용하여 나노 인덴테이션 리소그래피 연구를 진행하였다. 그 첫번째 연구는 전자빔 리소그래피로는 제작할 수 없는 바이오 필름 상에 나노 및 마이크로 패턴을 형성함으로써 전자빔 리소그래피의 취약점을 보완할 수 공정 방법이 될 수 있음을 제시하는 것이며, 두번째 연구는 나노 인덴테이션의 근본적인 문제점인 벌지를 선택적으로 제거하는 연구이다. 우선 다기능성 원자현미경 활용의 첫번째 연구로는 바이오 필름상에 나노/마이크로 패턴을 형성하는 일이다. 이 패턴된 바이오 필름은 비행 시간 2 차 이온 질량 분석 (TOF-SIMS)의 화학적 성분 이미징 및 깊이 분석에 유용한 강력한 시료로 사용될 수 있다. TOF-SIMS 분석에서 Arn + 가스 클러스터 이온 소스 (GCIB)는 주로 표면 분석의 소스뿐만 아니라 낮은 손상 단면 및 분자 깊이 프로파일 링 실험을 위한 빠른 침식 속도를 갖는 침식 소스로서 널리 사용되었다. 그러나 SIMS 분석에서 3D depth profile에 대한 침식 메커니즘을 이해하려면 잘 정의 된 3D 유기 미세 패턴으로 보정해야 하는데, 이때 나노 인덴테이션 기술을 이용한다. 이 기법은 TOF-SIMS의 3D 화학적 성분 분석/이미징을위한 표준 바이오 시료로 사용될 것으로 기대한다. 두번째 인덴테이션 활용 연구는 탐침이 소프트 필름을 누를 때 발생하는 벌지를 선택적으로 제거하는 연구로써, PMMA 필름이 나노 패턴 형성층이 되도록 사용한다. 그동안 벌지는 인덴테이션 리소그래피의 발전을 저해하는 가장 큰 요인으로써 선택적인 제거가 어려운 것으로 알려져 있었다. 하지만 이 논문에서는 현상액을 이용한 간단한 방식으로 다단계의 벌지 없는 패터닝 방식을 최초로 소개함으로써 새로운 차원의 리소그래피 기법을 제안하고 있다. 또한 이 기법은 3차원 나노 패턴을 성공적으로 복제 몰드에 전사할 수 있으므로 공정 비용 절감 효과는 물론이고, 다양한 연구 분야에서 이를 활용할 수 있을 것으로 기대한다.Abstract ............................... iv List of Figures ....................... xiii List of Tables ........................ xxi Chapter 1 Introduction 1 1.1 Multifunctional atomic force microscopy 1 1.2 Background on development of external stage for low noise AFM 2 1.3 Industrial applications for low noise atomic force microscopy 4 1.3.1 Critical dimension 4 1.3.2 Emergence of ultrathin films 7 1.4 Applications of indentation lithography using low noise atomic force microscopy 8 1.4.1 Demand for biological applications 8 1.4.2 Various lithography techniques 13 1.4.3 Strengths and limitations of AFM indentation lithography 13 1.5. The aims of this study 15 1.6. Reference 16 Chapter 2 Development of external automation stage for LN-AFM 25 2.1 Configurations of LN-AFM 25 2.2 Development of independent external stage 29 2.2.1 Configurations of the external stage 29 2.2.2 Position adjustment method 34 2.2.3 Position accuracy test 38 2.3. Reference 45 Chapter 3 Industrial applications using the LN-AFM with the external stage 47 3.1 Industrial demands 47 3.2 Critical dimension measurements 49 3.2.1 Vector approach probing method 49 3.2.2 Advantages and limitations 50 3.2.3 CD measurement using vertical structure 50 3.2.4 Tip wear test 55 3.3 Critical roughness measurements 58 3.3.1 Fabrication of ultrathin film using atomic layer deposition 58 3.3.2 Reliability of surface roughness measurements 60 3.3.3 Interfacial effects using roughness scaling method 63 3.3.4 Definition of critical roughness 68 3.3.5 Effectiveness of the critical roughness 74 3.3.6 Inline applications for the morphology analysis of ultrathin hafnium oxide films 76 3.4. Reference 81 Chapter 4 Applications of indentation lithography 88 4.1 Patterned organic films for 3D depth profiles of TOF-SIMS imaging 88 4.1.1 Fabrication method of organic dual layer for 3D TOF-SIMS 88 4.1.2 Results for organic dual layer for 3D TOF-SIMS 90 4.1.3 Fabrication issues of patterned organic dual layer 92 4.1.4 3D depth profile of patterned organic dual layer 97 4.2 Bulge-free indentation technique 100 4.2.1 PMMA bulge removal using IPA/DI developer 100 4.2.2 Mechanism study on the selective bulge removal process 105 4.2.3 Optimal condition for bulge-free indentation 108 4.2.4 3D bulge-free nano-patterns 112 4.3. Reference 115 Chapter 5 Conclusion 119 5.1 Discussion and conclusion 119 5.2 Reference 124 국 문 초 록 126Docto

Properties and behaviour of Pb-free solders in flip-chip scale solder interconnections

Due to pending legislations and market pressure, lead-free solders will replace Sn–Pb solders in 2006. Among the lead-free solders being studied, eutectic Sn–Ag, Sn–Cu and Sn–Ag–Cu are promising candidates and Sn–3.8Ag–0.7Cu could be the most appropriate replacement due to its overall balance of properties. In order to garner more understanding of lead-free solders and their application in flip-chip scale packages, the properties of lead free solders, including the wettability, intermetallic compound (IMC) growth and distribution, mechanical properties, reliability and corrosion resistance, were studied and are presented in this thesis. [Continues.

Advanced modeling of planarization processes for integrated circuit fabrication

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 215-225).Planarization processes are a key enabling technology for continued performance and density improvements in integrated circuits (ICs). Dielectric material planarization is widely used in front-end-of-line (FEOL) processing for device isolation and in back-end-of-line (BEOL) processing for interconnection. This thesis studies the physical mechanisms and variations in the planarization using chemical mechanical polishing (CMP). The major achievement and contribution of this work is a systematic methodology to physically model and characterize the non-uniformities in the CMP process. To characterize polishing mechanisms at different length scales, physical CMP models are developed in three levels: wafer-level, die-level and particle-level. The wafer-level model investigates the CMP tool effects on wafer-level pressure non-uniformity. The die-level model is developed to study chip-scale non-uniformity induced by layout pattern density dependence and CMP pad properties. The particle-level model focuses on the contact mechanism between pad asperities and the wafer. Two model integration approaches are proposed to connect wafer-level and particle-level models to the die-level model, so that CMP system impacts on die-level uniformity and feature size dependence are considered. The models are applied to characterize and simulate CMP processes by fitting polishing experiment data and extracting physical model parameters. A series of physical measurement approaches are developed to characterize CMP pad properties and verify physical model assumptions. Pad asperity modulus and characteristic asperity height are measured by nanoindentation and microprofilometry, respectively. Pad aging effect is investigated by comparing physical measurement results at different pad usage stages. Results show that in-situ conditioning keeps pad surface properties consistent to perform polishing up to 16 hours, even in the face of substantial pad wear during extended polishing. The CMP mechanisms identified from modeling and physical characterization are applied to explore an alternative polishing process, referred to as pad-in-a-bottle (PIB). A critical challenge related to applied pressure using pad-in-a-bottle polishing is predicted.by Wei Fan.Ph.D

Reliability Analysis of Electrotechnical Devices

This is a book on the practical approaches of reliability to electrotechnical devices and systems. It includes the electromagnetic effect, radiation effect, environmental effect, and the impact of the manufacturing process on electronic materials, devices, and boards

SCANNING TUNNELING MICROSCOPY STUDIES OF GROWTH MEDIUM & TEMPERATURE DEPENDENT STRUCTURAL PHASES OF ALKANETHIOL SELF-ASSEMBLED MONOLAYERS, REACTIVE SELF-ASSEMBLED MONOLAYERS, & FLAT GOLD NANOPARTICLE/INDIUM TIN OXIDE SUBSTRATES AND A SCANNING SURFAC

Self-assembled monolayers (SAMs) of alkanethiolates on Au(111) represent promising platforms to study the molecular surfaces and interfaces for applications ranging from molecular electronics, nanophotonics to biology. Understanding the effect of growth conditions on SAMs particularly on their structural features is important from both fundamental and applied points of view. Knowledge of SAM structural features and structural phase transitions provides important insights into molecular packing for the control of the molecular self-assembly.We compared SAMs grown from different media, from 1 mM C10 solution in decalin, hexadecane and triethylene glycol and from C10 vapor. We present a molecularly-resolved scanning tunneling microscopy study showing the dependence of the SAM structure on the growth conditions. We have established conditions for making samples almost vacancy islands (VI) free with very large SAM domains of (2&amp;#8730;3 &#215; 3)rect. superstructure and (&amp;#8730;3 &#215; 4&amp;#8730;3)R30&#176; striped phase and investigated the orientation of low-index step edges of Au(111) for normal and striped-phase SAMs. We showed that the striped phase is stable to converting to (2&amp;#8730;3 &#215; 3)rect. below 40 &#176;C.We demonstrate that flat gold nanoparticles (FGNPs) supported on indium tin oxide glass (ITO) are excellent substrates for molecularly-resolved STM imaging of alkanethiol SAMs. Nanoparticles were characterized using STM, TEM, and SEM techniques. Surface treatment techniques, Ar/O2 and H2 plasma treatments, dry thermal annealing and exposures to UV/O3, were used to prepare the surfaces of FGNPs supported on ITO and Au/mica substrates for high-resolution STM imaging of alkanethiol SAMs.We developed a convergent approach to functionalize SAM surfaces. Ordered mixed monolayers comprised of alkanethiols and azidoalkanethiols islands are formed and subsequent IMesCulBr catalyzed [3+2] "click" cycloaddition reaction with substituted alkyne introduced dilute substituent onto the ordered surface.Mechanical stress is one of the major factors in current design and manufacture of very large scale integrated (VLSI) devices. Mechanical stress in deep sub-micron silicon technologies can drastically alter carrier mobility (e.g., approximately 25% dependent on device geometry). This affects the device performance. Current in-line production stress metrology is conducted only at a wafer monitor level. The available stress measurement techniques such as micro-Raman spectroscopy, nano beam diffraction (NBD), converging electron beam diffraction (CEBD) either do not have required resolution or they require complex data interpretation. We present a method for measuring mechanical stress in deep sub-micron silicon devices with high spatial resolution using scanning Kelvin probe force microscopy and scanning surface photovoltage (SSPVM) techniques

Factories of the Future

Engineering; Industrial engineering; Production engineerin

Microelectromechanical Systems and Devices

The advances of microelectromechanical systems (MEMS) and devices have been instrumental in the demonstration of new devices and applications, and even in the creation of new fields of research and development: bioMEMS, actuators, microfluidic devices, RF and optical MEMS. Experience indicates a need for MEMS book covering these materials as well as the most important process steps in bulk micro-machining and modeling. We are very pleased to present this book that contains 18 chapters, written by the experts in the field of MEMS. These chapters are groups into four broad sections of BioMEMS Devices, MEMS characterization and micromachining, RF and Optical MEMS, and MEMS based Actuators. The book starts with the emerging field of bioMEMS, including MEMS coil for retinal prostheses, DNA extraction by micro/bio-fluidics devices and acoustic biosensors. MEMS characterization, micromachining, macromodels, RF and Optical MEMS switches are discussed in next sections. The book concludes with the emphasis on MEMS based actuators

Journal of Telecommunications and Information Technology, 2009, nr 4

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