Development and testing of a micromachined probe card.

This thesis is concerned with the design, fabrication and testing of micro scale probes. The probes were designed to act as temporary electrical connections to allow wafer level testing of integrated circuits. The work initially focused on the creation of free standing nickel cantilevers, angled up from the substrate with probe tips at the free end. These were fabricated using a novel method, combining pseudo grey scale lithography and thick photoresist sacrificial layers. Detailed analysis of the fabrication method, in particular the resist processing and lithography was undertaken and the limitations of the method explored.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Micro-fabrication of bio-MEMS based force sensor to measure the force response of living cells

Understanding how a living cell behaves has become a very important topic in today’s research field. Hence, different sensors and testing devices have been designed to test the mechanical properties of these living cells. This thesis presents a method of micro-fabricating a bio-MEMS based force sensor which is used to measure the force response of living cells. Initially, the basic concepts of MEMS have been discussed and the different micro-fabrication techniques used to manufacture various MEMS devices have been described. There have been many MEMS based devices manufactured and employed for testing many nano-materials and bio-materials. Each of the MEMS based devices described in this thesis use a novel concept of testing the specimens. The different specimens tested are nano-tubes, nano-wires, thin film membranes and biological living cells. Hence, these different devices used for material testing and cell mechanics have been explained. The micro-fabrication techniques used to fabricate this force sensor has been described and the experiments preformed to successfully characterize each step in the fabrication have been explained. The fabrication of this force sensor is based on the facilities available at Michigan Technological University. There are some interesting and uncommon concepts in MEMS which have been observed during this fabrication. These concepts in MEMS which have been observed are shown in multiple SEM images

Scanning thermal microscopy using nanofabricated probes

Novel atomic force microscope (AFM) probes with integrated thin film thermal sensors are presented. Silicon micromachining and high resolution electron beam lithography (EBL) have been used to make batch fabricated, functionalised AFM probes. The AFM tips, situated at the ends of Si3N4 cantilevers, are shaped either as truncated pyramids or sharp triangular asperites. The former gives good thermalisation of the sensor to the specimen for flat specimens whereas the latter gives improved access to highly topographic specimens. Tip radii for the different probes are 1 m and 50 nm respectively. A variety of metal structures have been deposited on the tips using EBL and lift-off to form Au/Pd thermocouples and Pd resistance thermometer/heaters. Sensor dimensions down to 35 nm have been demonstrated. In the case of the sharp triangular tips, holes were etched into parts of the cantilever in order to provide self alignment of the sensor to the tip. On the pyramidal tips it has been shown that multiple sensors can be made on a single tip with good definition and matching between sensors. A conventional AFM was constructed in order to test the micromachined thermal probes. During scans of a photothermal test specimen using improved access thermocouple probes, 80 nm period metal gratings were thermally resolved. This is equivalent to a thermal lateral resolution of 40 nm. Pyramidal tips with a resistance thermometer/heater, which were made for the microscopy and analysis of polymers, have been showed by others to produce high resolution thermal conductivity images. The probes have also been shown to be capable of locally heating a polymer specimen and thermomechanically measuring phase changes in small volumes of material. Also presented here is a study of scanning thermal microscopy of semiconductor structures using a commercial AFM. Included are scans of several specimens using both commercial andthe new micromachined probes. Subsurface images of voids buried under a SiO2 passivation layer were taken. It is shown that contrast caused by thermal conductivity differences in the specimen may be detected at a depth of over 200 nm

Design, Fabrication, Testing of CNT Based ISFET and Characterization of Nano/Bio Materials Using AFM

A combination of Carbon Nanotubes (CNTs) and Ion Selective Field Effect Transistor (ISFET) is designed and experimentally verified in order to develop the next generation ion concentration sensing system. Micro Electro-Mechanical System (MEMS) fabrication techniques, such as photolithography, diffusion, evaporation, lift-off, packaging, etc., are required in the fabrication of the CNT-ISFET structure on p-type silicon wafers. In addition, Atomic Force Microscopy (AFM) based surface nanomachining is investigated and used for creating nanochannels on silicon surfaces. Since AFM based nanomanipulation and nanomachining is highly controllable, nanochannels are precisely scratched in the area between the source and drain of the FET where the inversion layer is after the ISFET is activated. Thus, a bundle of CNTs are able to be aligned inside a single nanochannel by Dielectrophoresis (DEP) and the drain current is improved greatly due to CNTs` remarkable and unique electrical properties, for example, high current carrying capacity. ISFET structures with or without CNTs are fabricated and tested with different pH solutions. Besides the CNT-ISFET pH sensing system, this dissertation also presents novel AFM-based nanotechnology for learning the properties of chemical or biomedical samples in micro or nano level. Dimensional and mechanical property behaviors of Vertically Aligned Carbon Nanofibers (VACNFs) are studied after temperature and humidity treatment using AFM. Furthermore, mechanical property testing of biomedical samples, such as microbubbles and engineered soft tissues, using AFM based nanoindentation is introduced, and the methodology is of great directional value in the area

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

Adhesion and mechanical properties of PDMS-based materials probed with AFM: A review

This work was supported by Russian Science Foundation project grant 18-19-00645 "Adhesion of polymer-based soft materials: from liquid to solid-.Polydimethylsiloxane (PDMS) is the most widely used silicon-based organic polymer, and is particularly known for its unusual rheological properties. PDMS has found extensive usage in various fields ranging from microfluidics and flexible electronics to cosmetics and food industry. In certain applications, like e.g. dry adhesives or dry transfer of 2D materials, adhesive properties of PDMS play crucial role. In this review we focus on probing the mechanical and adhesive properties of PDMS by means of atomic force microscopy (AFM). Main advantages and limitations of AFM-based measurements in comparison to macroscopic tests are discussed.Russian Science Foundation 18-19-00645; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Mode I and Mode II Measurements For Stiction Failed Micro-Electro-Mechanical Systems

Among MicroElectroMechanical Systems (MEMS), the most common type of failure is stiction. Stiction is the unintended adhesion between two surfaces when they are in close proximity to each other. Various studies have been conducted in recent years to study stiction. Our research group has shown the in-service repair of the stiction failed MEMS devices is possible with structural vibrations. In order to further understand this phenomenon and better predict, theoretically, the onset of repair we have constructed an apparatus to determine the Mode I, II, and III interfacial adhesion energies of MEMS devices failed on a substrate. Though our method is general, we are specifically focused on devices created using the SUMMiT V process. An apparatus has been constructed that has 8 degrees-of-freedom between the MEMS device, the surface on which the device is failed, and a scanning interferometric microscope. Deflection profiles of stiction failed MEMS (micro-cantilevered beams 1000 microns long, 30 microns wide, and 2.3 microns thick) have their deflection profiles measured with nanometer resolution by a scanning interferometric microscope. Using the experimental apparatus that is constructed, we determine the Mode I and Mode II interfacial adhesion energies using two methodologies. The first method utilizes the peel test scheme to determine pure Mode-I and Mixed Mode (Mode I and II) interfacial adhesion energies. In order to determine the values for the interfacial adhesion energies a nonlinear model was developed for the deflection of a beam that accounts for its stretching. Energy methods are then utilized to determine interfacial adhesion energies. Using the same experimental apparatus Mode II interfacial adhesion energies are measured directly with a novel technique developed in this work. This experimental method for measuring the Mode II interfacial adhesion energies for stiction failed MEMS devices uses a microcantilever beam (1500 μm long, 30 μm wide and 2.3 μm thick) attached to MEMS actuator with fix-fix beam flexure. Deflection of the spring is measured with the vernier scale of the actuator. Then a nonlinear elastic model for the fix—fix beam flexure is used to determine the interfacial adhesion energy between the failed microcantilever beam and the surface. A theory is developed to measure the strain energy release rates with finite crack growth, which gives the upper bounds of interfacial adhesion energy for Mode II fracture problem. A separate theory is developed for infinitesimal crack growth, which gives the exact interfacial adhesion energy of the Mode II fracture problem. Because the surface roughness plays an important role in the adhesion of MEMS structures, the surfaces of all structures have been characterized with an Atomic Force Microscope (AFM)