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This paper focuses mainly on the development of dry etching for structures of high aspect ratios, which will offer the potential to manufacture micro-sensors, micro-engines, micro-turbines, micro-actuators, and electronic circuits onto a... more
This paper focuses mainly on the development of dry etching for structures of high aspect ratios, which will offer the potential to manufacture micro-sensors, micro-engines, micro-turbines, micro-actuators, and electronic circuits onto a single IC silicon chip. This technology is based on the highly anisotropic and selective dry etching of Simonocrystals. The suitability of reactive ion etching for the fabrication of micro electro mechanical systems (MEMS) has been evaluated by characterising the change of lateral dimensions vs. depth in etching deep structures in silicon. Fluorine, chlorine -and bromine-containing gases have provided the basis for this investigation. A conventional planar RIE (Reactive Ion Etching) reactor has been used, in some cases with magnetic field enhancement or with the ICP (Inductive Coupled Plasma) Source and low substrate temperatures. For reactive ion etching based on Cl2 or Cl2/HBr plasma, a slightly “positive” (top wider than bottom) slope is achieved when structures are etched with a depth of several 10 pm, whereas a “negative” slope is obtained when etching with an SF6/CCl2F2 based plasma. Pattern transfer with vertical walls is obtained for reactive ion etching based on SF6 (with O2 added) when maintaining the substrate at Iow temperature (in range ≈-100–). Further optimization of plasma chemistries and reactive ion etching procedures should result in runout depths of the order of 0.1 µm/100 gm in Si as well as in organic materials. Etching processes are demonstrated in the realisation in Si microturbine. Axles or stators (nonmoving parts) are etched into the original Si-wafer. The movable parts (rotors, beams, etc.) are prepared from electrochemically etched Si-membranes with defined thicknesses. Then all movable parts are created lithographically on the SiNxOy surface. This is followed by dry etching the mono-crystalline Si-membrane down to the SiNxOy sacrificial layer on the back side of the membrane by an RIE-process. The wafer with the movable parts is flipped onto the wafer with the already etched axle and then positioned and centred. The SiNxOy sacrificial layer is then dissolved by a chemical wet or vapour etch process. Subsequent bonding with a Pyrex glass wafer seals the parts. The topic of lithography (masked ion beam lithography, MIBL), which delivers high resolution and large focus depths as well as e-beam lithography with tunnel-tips, is also addressed in this paper.
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This work presents the detailed description of the formation process of the silicon microreactors and micromechanical structures which will dominate the near future. The description is based mainly on the author’s experience and includes... more
This work presents the detailed description of the formation process of the silicon microreactors and micromechanical structures which will dominate the near future. The description is based mainly on the author’s experience and includes a description of the dry etching of silicon by means of different halogen plasmas. The well established methods of microsystem technology allow the cheap and fast production of silicon based microtools in large numbers via batch processing.
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ABSTRACT The atomic force microscope (AFM) is a very sensitive instrument to examine the topography of surfaces and their properties. The sensitivity of the AFM depends on the choice of the detector system, which is used to observe the... more
ABSTRACT The atomic force microscope (AFM) is a very sensitive instrument to examine the topography of surfaces and their properties. The sensitivity of the AFM depends on the choice of the detector system, which is used to observe the cantilever deflection. A cantilever with integrated Wheatstone piezoresistive bridge as a deflection sensor was used in experiments. We describe noise properties of the piezoresistive Wheatstone bridge cantilever and show examples of topography measurements in contact and noncontact mode.
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The paper presents an application of the Wheatstone piezoresistive bridge in advanced AFM investigations. We have utilized this cantilever in investigations of the contact and noncontact modes, and in investigations of lateral forces and... more
The paper presents an application of the Wheatstone piezoresistive bridge in advanced AFM investigations. We have utilized this cantilever in investigations of the contact and noncontact modes, and in investigations of lateral forces and modulation load force microscopy. In the case of non-homogeneous surfaces, investigations of various surface parameters and topography observations are very important. Such surfaces are used in most industrial applications, and investigations of their properties at the nanometre scale is of great interest.
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In this paper we discuss the capabilities of micromachined piezoresistive silicon cantilevers regarding their application for surface metrology [1]. Measurements were performed using contact-mode Atomic Force Microscopy (AFM) and... more
In this paper we discuss the capabilities of micromachined piezoresistive silicon cantilevers regarding their application for surface metrology [1]. Measurements were performed using contact-mode Atomic Force Microscopy (AFM) and contact-resonance mode, respectively [2]. The contact-mode AFM measurements were carried out inside a Scanning Electron Microscope (SEM) vacuum chamber enabling correlative scanning probe and electron microscopy.
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In this work, we report progress on developing a multipurpose scanning probe cantilever applying gallium nitride nanowires as the probe tip. Gallium nitride nanowires possess high potential as probes due to their straight profile, tunable... more
In this work, we report progress on developing a multipurpose scanning probe cantilever applying gallium nitride nanowires as the probe tip. Gallium nitride nanowires possess high potential as probes due to their straight profile, tunable electrical and optical properties, high Young’s Modulus, durability, and high-yield fabrication process. Their wide bandgap enables them to be pumped to emit ultraviolet pulses which can be used for optical imaging and spectroscopy. They can be doped during growth to be electrically conductive, and their sharp tips obtained during epitaxial growth enable confinement of a high electric field at tip–sample interface. Their sharp tips are obtained during fabrication by their epitaxial growth which eliminates the need for postprocess sharpening that is typically required for standard STM tips. We present results of using gallium nitride nanowires for scanning tunnel microscopy applications of atomic-resolution imaging and lithography, and atomic force microscopy applications of imaging and lithography in vacuum and atmospheric environments.
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The field of optical lithography is subject to intense research and has gained enormous improvement. However, the effort necessary for creating structures at the size of 20 nm and below is considerable using conventional technologies.... more
The field of optical lithography is subject to intense research and has gained enormous improvement. However, the effort necessary for creating structures at the size of 20 nm and below is considerable using conventional technologies. This effort and the resulting financial requirements can only be tackled by few global companies and thus a paradigm change for the semiconductor industry is conceivable: custom design and solutions for specific applications will dominate future development (Fritze in: Panning EM, Liddle JA (eds) Novel patterning technologies. International society for optics and photonics. SPIE, Bellingham, 2021. 10.1117/12.2593229). For this reason, new aspects arise for future lithography, which is why enormous effort has been directed to the development of alternative fabrication technologies. Yet, the technologies emerging from this process, which are promising for coping with the current resolution and accuracy challenges, are only demonstrated as a proof-of-conc...
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Although the field of optical lithography is highly investigated and numerous improvements are made, structure sizes smaller than 20 nm can only be achieved by considerable effort when using conventional technology. To cover the upcoming... more
Although the field of optical lithography is highly investigated and numerous improvements are made, structure sizes smaller than 20 nm can only be achieved by considerable effort when using conventional technology. To cover the upcoming tasks in future lithography, enormous exertion is put into the development of alternative fabrication technologies in particular for micro- and nanotechnologies that are capable of measuring and patterning at the atomic scale in growing operating areas of several hundred square millimetres. Many new technologies resulted in this process, and are promising to overcome the current limitations1, 2, but most of them are demonstrated in small areas of several square micrometers only, using state-of-the-art piezo stages or the like. At the Technische Universitat Ilmenau, the NanoFabrication Machine 100 (NFM-100) was developed, which serves as an important experimental platform for basic research in the field of scale-spanning AFM tip-based and laser-based nanomeasuring and nanofabrication for simultaneous subnanometre measuring and structuring on surfaces up to O100 mm. This machine can be equipped with several probing systems like AFM, laser focus probes and 3D-micro probes as well as tools for different nanofabrication technologies like tip-based technologies, optical technologies and mechanical two-dimensional technologies in a large working range with subnanometre reproducibility and uncertainty. In this paper, the specifics and advantages of the NFM-100 will be described as well as nanofabrication technologies that are currently worked on e.g. advanced scanning proximal probe lithography based on Fowler-Nordheim-electron-field emission, direct laser writing and UV-nanoimprint lithography.
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The development of next nodes of nano-electronic devices requires mask-less techniques for fast prototyping and analysis of ultimately down-scaled devices or for fabrication of templates for nanoimprint based high-volume manufacturing.... more
The development of next nodes of nano-electronic devices requires mask-less techniques for fast prototyping and analysis of ultimately down-scaled devices or for fabrication of templates for nanoimprint based high-volume manufacturing. Moreover, the atomic force microscopy (AFM) of large surfaces with acceptable speed becomes an issue with the introduction of large-sized wafers. The authors have designed an AFM system which is capable of field-emission scanning probe lithography on 150 mm wafers providing superior stitching accuracy better than 3 nm. The system is also providing noncontact, high-resolution 3D imaging employing active probes (i.e., piezoresistive self-sensing and thermo-mechanically self-actuated probes) and capable to operate with an array of four cantilevers. A high-precision X-Y-θ stage with 10 nm positioning accuracy and with 360° rotation capability enables the highest placement precision and cost effective large scanning field imaging.
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Single-digit nanometer lithography is a basic requirement for beyond CMOS devices. To address this lithography challenge, a variety of different lithographic methods were developed. Here, the authors present the possibility of field... more
Single-digit nanometer lithography is a basic requirement for beyond CMOS devices. To address this lithography challenge, a variety of different lithographic methods were developed. Here, the authors present the possibility of field emission scanning probe lithography (FE-SPL) with a diamond tip in order to enhance the lifetime of the used tip. A superior mechanical hardness and a good electron emission stability even after a total of 48 h of lithographic patterning by FE-SPL were proven, and features with half pitches down to 15 nm have been fabricated.
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Electrical operation of room-temperature (RT) single dopant atom quantum dot (QD) transistors, based on phosphorous atoms isolated within nanoscale SiO2 tunnel barriers, is presented. In contrast to single dopant transistors in silicon,... more
Electrical operation of room-temperature (RT) single dopant atom quantum dot (QD) transistors, based on phosphorous atoms isolated within nanoscale SiO2 tunnel barriers, is presented. In contrast to single dopant transistors in silicon, where the QD potential well is shallow and device operation limited to cryogenic temperature, here, a deep (∼2 eV) potential well allows electron confinement at RT. Our transistors use ∼10 nm size scale Si/SiO2/Si point-contact tunnel junctions, defined by scanning probe lithography and geometric oxidation. “Coulomb diamond” charge stability plots are measured at 290 K, with QD addition energy ∼0.3 eV. Theoretical simulation gives a QD size of similar order to the phosphorous atom separation ∼2 nm. Extraction of energy states predicts an anharmonic QD potential, fitted using a Morse oscillator-like potential. The results extend single-atom transistor operation to RT, enable tunneling spectroscopy of impurity atoms in insulators, and allow the energy ...
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In this work, the fabrication and operation of an active parallel cantilever device integrating four self-sensing and self-actuating probes in an array is presented. The so called “Quattro” cantilever system is controlled by a... more
In this work, the fabrication and operation of an active parallel cantilever device integrating four self-sensing and self-actuating probes in an array is presented. The so called “Quattro” cantilever system is controlled by a multichannel field programmable gate array (FPGA) controller. The integrated cantilever devices are fabricated on the basis of a silicon-on-insulator wafer using surface micromachining and gas chopping plasma-etching processes [I. W. Rangelow, J. Vac. Sci. Technol., A 21, 1550 (2003)]. The unique design of the active cantilever probes provides both patterning and readout capabilities [Kaestner et al., J. Micro-Nanolithogr. MEMS 14, 031202 (2015)]. The thermomechanical actuation allows the individually operation of each cantilever in static and dynamic modes. This enables a simultaneous atomic force microscopy operation of all cantilevers in an array, while the piezoresistive read-out of the cantilever bending routinely ensures atomic resolution at a high imagi...
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The conventional optical lever detection technique involves optical components and its precise mechanical alignment. An additional technical limit is the weight of the optical system, in case a top-scanner is used in high speed and high... more
The conventional optical lever detection technique involves optical components and its precise mechanical alignment. An additional technical limit is the weight of the optical system, in case a top-scanner is used in high speed and high precision metrology. An alternative represents the application of self-actuated AFM cantilevers with integrated 2DEG piezoresistive deflection sensors. A significant improvement in performance of such cantilevers with respect to deflection sensitivity and temperature stability has been achieved by using an integrated Wheatstone bridge configuration. Due to employing effective cross-talk isolation and temperature drift compensation the performance of these cantilevers was significantly improved. In order to enhance the speed of AFM measurements we are presenting a fast cantilever-approach technology, Q-factor-control and novel adaptive scanning speed procedure. Examples of AFM measurements with high scanning speed (up to 200 lines/s) committed to advanced lithography process development are shown.
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The routine “on demand” fabrication of features smaller than 10 nm opens up new possibilities for the realization of many novel nanoelectronic, NEMS, optical and bio-nanotechnology-based devices. Based on the thermally actuated,... more
The routine “on demand” fabrication of features smaller than 10 nm opens up new possibilities for the realization of many novel nanoelectronic, NEMS, optical and bio-nanotechnology-based devices. Based on the thermally actuated, piezoresistive cantilever technology we have developed a first prototype of a scanning probe lithography (SPL) platform able to image, inspect, align and pattern features down to single digit nano regime. The direct, mask-less patterning of molecular resists using active scanning probes represents a promising path circumventing the problems in today’s radiation-based lithography. Here, we present examples of practical applications of the previously published electric field based, current-controlled scanning probe lithography on molecular glass resist calixarene by using the developed tabletop SPL system. We demonstrate the application of a step-and-repeat scanning probe lithography scheme including optical as well as AFM based alignment and navigation. In addition, sequential read-write cycle patterning combining positive and negative tone lithography is shown. We are presenting patterning over larger areas (80 x 80 μm) and feature the practical applicability of the lithographic processes.
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We have designed, manufactured and measured performance of novel chemical gas sensors, which are based on conductivity modulation of discontinuous gold films on a dielectric substrate. The sensor elements were functionalized with... more
We have designed, manufactured and measured performance of novel chemical gas sensors, which are based on conductivity modulation of discontinuous gold films on a dielectric substrate. The sensor elements were functionalized with different calixarenes. Several volatile analytes were exposed and dynamical sensor responses were investigated. Physical principles of the sensor operation are discussed. Our results show applicability of the proposed approach for chemical sensing and recognition.
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Atomic Force Microscopy (AFM) is a capable to provide high resolution CD-metrology and precise defects analysis on large wafers, masks or displays. However, AFM is not enough productive for high-throughput industrial uses. Standard single... more
Atomic Force Microscopy (AFM) is a capable to provide high resolution CD-metrology and precise defects analysis on large wafers, masks or displays. However, AFM is not enough productive for high-throughput industrial uses. Standard single probe AFMs are showing low throughput as a serial imaging tools. The use of an array of four cantilevers as a Quattro-Array results in effective speed of 6 to 10 mm/s. An image size of 0.5mm x 0.2mm is achieved employing a piezoelectric positioner with a scan range of 200μm x 200μm and a resolution of 0.25nm (x,y) and 0.2nm (z), respectively. These capabilities are qualifying the Quattro-cantilever array system as fastest tool for. In this paper we present new results obtained with our Quattro-AFM high-throughput parallel SPM system that exhibits two key advances that are required for a successful deployment of SPM in time-efficient metrology, defect analysis and mask inspection.
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The fabrication process, application, and properties of a novel piezoresistive multiprobe with an integrated thermal tip deflection actuator are described in this article. The optimized fabrication process of the microprobe enables... more
The fabrication process, application, and properties of a novel piezoresistive multiprobe with an integrated thermal tip deflection actuator are described in this article. The optimized fabrication process of the microprobe enables high-frequency sensor operation and integration of a high sharp conical tip, which was additionally covered with titanium using atomic layer deposition to improve mechanical endurance and ensure electrical conductivity. This microprobe was applied in high-resolution self-assembled monolayer surface investigations in which the piezoresistive cantilever with the integrated thermal deflection actuator was excited at two of its flexural-resonant eigenmodes. The excited second eigenmode and phase show different contrasts com-pared with images recorded at the first eigenmode.
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ABSTRACT Two process flows for the fabrication of stencil masks have been developed. The PN Wafer Flow- and the SOI Wafer Flow Process. Membranes and stencil masks out of different 6 inch Si base wafers with 3 micrometers membrane... more
ABSTRACT Two process flows for the fabrication of stencil masks have been developed. The PN Wafer Flow- and the SOI Wafer Flow Process. Membranes and stencil masks out of different 6 inch Si base wafers with 3 micrometers membrane thickness and a membrane diameter between 120 mm and 126 mm were fabricated. The membrane stress depending on the material property and doping level has been determined. First metrology measurements have been carried out.
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Abstract Field Emission Scanning Probe Lithography (FE-SPL) is an enabling technology for prototyping of sub-10 nm high-performance electronic devices. However, due to the serial writing scheme this technology is rather slow. The purpose... more
Abstract Field Emission Scanning Probe Lithography (FE-SPL) is an enabling technology for prototyping of sub-10 nm high-performance electronic devices. However, due to the serial writing scheme this technology is rather slow. The purpose of this work is the demonstration of a mix-and-match process in combination with cryogenic etching in order to fabricate templates for Nanoimprint Lithography (NIL). We describe (i) the fabrication of a micron-sized electrode layout on a 1.5 mm × 1.5 mm area by means of fast Direct Laser Writing (DLW), (ii) the subsequent stitching of nano-sized features on the same resist layer using high-resolution FE-SPL and (iii) the pattern transfer into silicon. IC manufacturing requires both, large throughputs with critical feature size smaller than 5 nm. Therefore, the motivation of our project is to develop a lithographic process for nano-electronic devices with critical feature size smaller than 5 nm, while the rest of the device sizes are 100 nm or larger. Thus, a possible SET template was designed for future high-throughput NIL.
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Tip-based electron beam induced deposition is performed using field emission of low-energy electrons from the tip of an active (i.e., self-sensing and self-actuating) atomic force microscope cantilever inside a scanning electron... more
Tip-based electron beam induced deposition is performed using field emission of low-energy electrons from the tip of an active (i.e., self-sensing and self-actuating) atomic force microscope cantilever inside a scanning electron microscope. By using the active cantilever for feature placement and metrology combined with fast switching between field-emission and noncontact imaging mode, high placement accuracy and time-efficient, precise 3D measurement of the deposits are enabled. First results on the effect of electron energy and exposure dose on the growth rates and dimensions of the deposits are presented, and the potential to increase spatial resolution due to the enhanced localization of the dissociation reactions induced by the low-energy electrons is discussed.
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Next generation electronic devices like single electron transistors (SETs) operating at room temperature (RT) demand for high-resolution patterning techniques and simultaneously cost-effective, high-throughput manufacturing. Thereby,... more
Next generation electronic devices like single electron transistors (SETs) operating at room temperature (RT) demand for high-resolution patterning techniques and simultaneously cost-effective, high-throughput manufacturing. Thereby, field-emission scanning probe lithography (FE-SPL) is a direct writing method providing high-resolution and high-quality nanopatterns. SET devices prepared by FE-SPL and plasma etching at cryogenic substrate temperature were shown to operate at RT [C. Lenk et al., Microelectron. Eng. 192, 77 (2018); Z. Durrani, M. Jones, F. Abualnaja, C. Wang, I. W. Rangelow, M. Kaestner, S. Lenk, C. Lenk, and A. Andreev, J. Appl. Phys. 124, 144502 (2018); I. W. Rangelow et al., J. Vac. Sci. Technol. B 34, 06K202 (2016)]. Nevertheless, FE-SPL lacks in writing speed and large area manufacturing capability required for industrial device manufacturing. This can be overcome by combining FE-SPL with nanoimprint lithography (NIL), which enables the replication of high-resolut...
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In this paper the authors compare methods used for piezoresistive microcantilevers actuation for the atomic force microscopy (AFM) imaging in the dynamic shear force mode. The piezoresistive detection is an attractive technique comparing... more
In this paper the authors compare methods used for piezoresistive microcantilevers actuation for the atomic force microscopy (AFM) imaging in the dynamic shear force mode. The piezoresistive detection is an attractive technique comparing the optical beam detection of deflection. The principal advantage is that no external alignment of optical source and detector are needed. When the microcantilever is deflected, the stress is transferred into a change of resistivity of piezoresistors. The integration of piezoresistive read-out provides a promising solution in realizing a compact non-contact AFM. Resolution of piezoresistive read-out is limited by three main noise sources: Johnson, 1/f and thermomechanical noise. In the dynamic shear force mode measurement the method used for cantilever actuation will also affect the recorded noise in the piezoresistive detection circuit. This is the result of a crosstalk between an aluminium path (current loop used for actuation) and piezoresistors located near the base of the beam. In this paper authors described an elaborated in ITE (Institute of Electron Technology) technology of fabrication cantilevers with piezoresistive detection of deflection and compared efficiency of two methods used for cantilever actuation.
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Merging two state-of-the-art surface research techniques, in particular, atomic force microscopy (AFM) and scanning electron microscopy (SEM), within a single system is providing novel capabilities like direct visual feedback and... more
Merging two state-of-the-art surface research techniques, in particular, atomic force microscopy (AFM) and scanning electron microscopy (SEM), within a single system is providing novel capabilities like direct visual feedback and life-monitoring of tip-induced nanoscale interactions. In addition, the combination of AFM and SEM accelerates nanoscale characterization and metrology development. Here, the concept and first results of a novel AFM-integration into a high resolution scanning electron microscope and focused ion beam system for nanoscale characterization is presented. In this context, a six-axis AFM system using self-sensing thermomechanically transduced active cantilever was developed and integrated. The design of the developed AFM-integration is described and its performance is demonstrated. Results from combined examinations applying fast AFM-methods and SEM-image fusion, AFM-SEM combined metrology verification, and three dimensional-visualization are shown. Simultaneous ...
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Atomic force microscopy is a powerful topography imaging method used widely in nanoscale metrology and manipulation. A conventional Atomic Force Microscope (AFM) utilizes an optical lever system typically composed of a laser source,... more
Atomic force microscopy is a powerful topography imaging method used widely in nanoscale metrology and manipulation. A conventional Atomic Force Microscope (AFM) utilizes an optical lever system typically composed of a laser source, lenses and a four quadrant photodetector to amplify and measure the deflection of the cantilever probe. This optical method for deflection sensing limits the capability of AFM to obtaining images in transparent environments only. In addition, tapping mode imaging in liquid environments with transparent sample chamber can be difficult for laser-probe alignment due to multiple different refraction indices of materials. Spurious structure resonance can be excited from piezo actuator excitation. Photothermal actuation resolves the resonance confusion but makes optical setup more complicated. In this paper, we present the design and fabrication method of coated active scanning probes with piezoresistive deflection sensing, thermomechanical actuation and thin ...
Research Interests: Materials Science, Optics, Sensors and Sensing, Imaging Science, Scanning Probe Microscopy, and 11 moreNanomaterials, Nanotechnology, Atomic Force Microscopy, Medicine, LabVIEW, Opacity, MEMS design: Sensors and Actuators, Cantilever, Piezoresitive Microcantilever, Nano Fabrication, and Modeling and Simulation of Cantilever Sensor
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Atomic Force Microscopes are capable to provide non-destructive high resolution, CD-metrology and precise defect analysis. However, a conventional AFM has not enough throughput for today’s large scale semiconductor manufacturing. The... more
Atomic Force Microscopes are capable to provide non-destructive high resolution, CD-metrology and precise defect analysis. However, a conventional AFM has not enough throughput for today’s large scale semiconductor manufacturing. The primary point remains the increase of the scanning area in case of large wafers, masks, displays or dies. Cantilever array-based AFMs are intended to increase the imaging throughput by parallelizing the work of many AFM probes that may be practiced by parallel AFM systems that are capable to operate autonomously. An active cantilever scheme makes it possible to sense electronically the deflection and individually to control the actuation of every cantilever in the array. Each cantilever in the array represents a self-sustaining AFM-hardware system for metrology and imaging. In that, the multiple parallel probes are forming many AFMs capable to work independently.
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ABSTRACT Under certain process conditions, plasma polymerization of fluoro-carbons on structured silicon samples shows two distinctive effects: First, the growth rate at a certain depth inside the trenches is considerably larger than at... more
ABSTRACT Under certain process conditions, plasma polymerization of fluoro-carbons on structured silicon samples shows two distinctive effects: First, the growth rate at a certain depth inside the trenches is considerably larger than at the shoulders, the trench bottom or other areas of the sidewall. Second, an initial sidewall texture is enlarged in the shape of the deposited polymer film. Profile simulations support the hypothesis that these effects are caused by ion-enhancement of the deposition rate in conjunction with geometrical shadowing of ion flux to concave areas of the rippled sidewalls.