Journal articles on the topic 'Microelectromechanical systems – Micromachining'
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1
Bhat, K. N. "Micromachining for Microelectromechanical Systems." Defence Science Journal 48, no. 1 (January 1, 1998): 5–19. http://dx.doi.org/10.14429/dsj.48.3863.
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Bustillo, J. M., R. T. Howe, and R. S. Muller. "Surface micromachining for microelectromechanical systems." Proceedings of the IEEE 86, no. 8 (1998): 1552–74. http://dx.doi.org/10.1109/5.704260.
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Esashi, Masayoshi. "Micromachine. Microelectromechanical Systems by Silicon Micromachining." Journal of the Institute of Television Engineers of Japan 50, no. 8 (1996): 1046–53. http://dx.doi.org/10.3169/itej1978.50.1046.
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Kota, S., G. K. Ananthasuresh, S. B. Crary, and K. D. Wise. "Design and Fabrication of Microelectromechanical Systems." Journal of Mechanical Design 116, no. 4 (December 1, 1994): 1081–88. http://dx.doi.org/10.1115/1.2919490.
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An attempt has been made to summarize some of the important developments in the emerging technology of microelectromechanical systems (MEMS) from the mechanical engineering perspective. In the micro domain, design and fabrication issues are very much different from those of the macro world. The reason for this is twofold. First, the limitations of the micromachining techniques give way to new exigencies that are nonexistent in the macromachinery. One such difficulty is the virtual loss of the third dimension, since most of the microstructures are fabricated by integrated circuit based micromachining techniques that are predominantly planar. Second, the batch-produced micro structures that require no further assembly, offer significant economical advantage over their macro counterparts. Furthermore, electronic circuits and sensors can be integrated with micromechanical structures. In order to best utilize these features, it becomes necessary to establish new concepts for the design of MEMS. Alternate physical forms of the conventional joints are considered to improve the manufacturability of micromechanisms and the idea of using compliant mechanisms for micromechanical applications is put forth. The paper also reviews some of the fabrication techniques and the micromechanical devices that have already been made. In particular, it discusses the fabrication of a motor-driven four-bar linkage using the “boron-doped bulk-silicon dissolved-wafer process” developed at The University of Michigan’s Center for Integrated Sensors and Circuits.
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Mehregany, Mehran, and Christian A. Zorman. "Surface Micromachining: A Brief Introduction." MRS Bulletin 26, no. 4 (April 2001): 289–90. http://dx.doi.org/10.1557/mrs2001.61.
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The rapid expansion of microelectromechanical systems (MEMS) into new application areas is due in large part to the development of surface-micromachining techniques that allow the fabrication of a wide variety of MEMS devices with structural components that can execute motion in at least one direction.
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Chircov, Cristina, and Alexandru Mihai Grumezescu. "Microelectromechanical Systems (MEMS) for Biomedical Applications." Micromachines 13, no. 2 (January 22, 2022): 164. http://dx.doi.org/10.3390/mi13020164.
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The significant advancements within the electronics miniaturization field have shifted the scientific interest towards a new class of precision devices, namely microelectromechanical systems (MEMS). Specifically, MEMS refers to microscaled precision devices generally produced through micromachining techniques that combine mechanical and electrical components for fulfilling tasks normally carried out by macroscopic systems. Although their presence is found throughout all the aspects of daily life, recent years have witnessed countless research works involving the application of MEMS within the biomedical field, especially in drug synthesis and delivery, microsurgery, microtherapy, diagnostics and prevention, artificial organs, genome synthesis and sequencing, and cell manipulation and characterization. Their tremendous potential resides in the advantages offered by their reduced size, including ease of integration, lightweight, low power consumption, high resonance frequency, the possibility of integration with electrical or electronic circuits, reduced fabrication costs due to high mass production, and high accuracy, sensitivity, and throughput. In this context, this paper aims to provide an overview of MEMS technology by describing the main materials and fabrication techniques for manufacturing purposes and their most common biomedical applications, which have evolved in the past years.
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Ermolov, Vladimir, Antti Lamminen, Jaakko Saarilahti, Ben Wälchli, Mikko Kantanen, and Pekka Pursula. "Micromachining integration platform for sub-terahertz and terahertz systems." International Journal of Microwave and Wireless Technologies 10, no. 5-6 (April 10, 2018): 651–59. http://dx.doi.org/10.1017/s175907871800048x.
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AbstractWe demonstrate a sub-terahertz (THz) and THz integration platform based on micromachined waveguides on silicon. The demonstrated components in the frequency range 225–325 GHz include waveguides, filters, waveguide vias, and low-loss transitions between the waveguide and the monolithic integrated circuits. The developed process relies on microelectromechanical systems manufacturing methods and silicon wafer substrates, promising a scalable and cost-efficient system integration method for future sub-THz and THz communication and sensing applications. Low-temperature Au/In thermo-compression and Au–Au laser bonding processes are parts of the integration platform enabling integration of millimeter-wave monolithic integrated circuits.
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Tao, Kai, Gui Fu Ding, Zhuo Qing Yang, Yan Wang, and Pei Hong Wang. "Fabrication and Characterization of Bonded NdFeB Microstructures for Microelectromechanical Systems Applications." Advanced Materials Research 211-212 (February 2011): 561–64. http://dx.doi.org/10.4028/www.scientific.net/amr.211-212.561.
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A micromachining technique has been developed for the fabrication of microscale polymer-bonded magnet. Two types of lithographically defined molds, photoresist mold and electroplated metal mold, were introduced. Photoresist mold is convenient, while electroplated metal mold can be fabricated on the glass or steel substrate which can bear much more compression. NdFeB films of thickness between 50 and 500 µm were prepared by micro-patterning of composites containing 83-95wt% of commercial NdFeB powder after curing at the room temperature. Magnetic properties mainly depend on the types and percentage of volume loading of magnetic powder. Coercivity of 772.4kA/m (9.70kOe), remanence of 275.1mT (2.751kG), and energy product of 22.6kJ/m3 (2.8MGOe) have been achieved. This easily developed magnet could be a promising candidate for applications in magnetic microelectromechanical systems (MEMS).
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Ramesham, Rajeshuni. "Fabrication of diamond microstructures for microelectromechanical systems (MEMS) by a surface micromachining process." Thin Solid Films 340, no. 1-2 (February 1999): 1–6. http://dx.doi.org/10.1016/s0040-6090(98)01370-4.
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Ballarini, R., R. L. Mullen, Y. Yin, H. Kahn, S. Stemmer, and A. H. Heuer. "The Fracture Toughness of Polysilicon Microdevices: A First Report." Journal of Materials Research 12, no. 4 (April 1997): 915–22. http://dx.doi.org/10.1557/jmr.1997.0131.
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Polysilicon microfracture specimens were fabricated using surface micromachining techniques identical to those used to fabricate microelectromechanical systems (MEMS) devices. The nominal critical J-integral (the critical energy release rate) for crack initiation, Jc, was determined in specimens whose characteristic dimensions were of the same order of magnitude as the grain size of the polysilicon. Jc values ranged from 16 to 62 N/m, approximately a factor of four larger than Jc values reported for single crystal silicon.
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Beeby, S. P., A. Blackburn, and N. M. White. "Silicon micromachining processes combined with thick-film printed lead zirconate titanate actuators for microelectromechanical systems." Materials Letters 40, no. 4 (August 1999): 187–91. http://dx.doi.org/10.1016/s0167-577x(99)00073-7.
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Lusk, Craig P., and Larry L. Howell. "Design Space of Single-Loop Planar Folded Micro Mechanisms With Out-of-Plane Motion." Journal of Mechanical Design 128, no. 5 (November 3, 2005): 1092–100. http://dx.doi.org/10.1115/1.2216734.
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Microelectromechanical systems (MEMS) are usually fabricated using planar processing methods such as surface micromachining, bulk micromachining, or LIGA-type fabrication. If a micro mechanism is desired that has motion out of the plane of fabrication, it can be a folded mechanism in its fabricated position. The desire to design MEMS for a wide range of out-of-plane motions has led to the need for a better theoretical understanding of the design space for folded mechanisms. Thus, this paper derives the design space of arbitrary planar folded mechanisms. This results in the definition of the orientation set measures equality condition (OSMEC) which can be used in constructing adjacency set patches and joining them to construct the design space. The results can be used to explore different properties of the mechanisms in the design space. One such property, the mechanisms’ folded length, is given as an example. Although MEMS provide the primary motivation for the work, the results are general and apply to other areas of application.
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Chen, Tao, Li Guo Chen, Ming Qiang Pan, and Li Ning Sun. "Study on MEMS Microgripper Integrated Vacuum Tool." Applied Mechanics and Materials 43 (December 2010): 471–75. http://dx.doi.org/10.4028/www.scientific.net/amm.43.471.
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This paper presents a hybrid type of microelectromechanical systems (MEMS) microgripper integrated with an electrostatic mechanism and vacuum technology. Vacuum tools are integrated in this microgripper in order to achieve a reliable and accurate manipulation of microobjects. The microgripper is fabricated by a surface and bulk micromachining technology. The pick and release micromanipulation of microobjects is accomplished by electrostatic driving force caused by comb structure and an auxiliary air pressure force from air pump. The performance of this new hybrid type of microgripper is experimentally demonstrated through the manipulation of 100–200μm polystyrene balls. Experimental results show that this microgripper can successfully fulfill the pick and release micromanipulation.
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Li, Jing Feng, Song Zhe Jin, and Yong Li. "Fabrication of Si3N4 Micro-Components by a Combined Microfabrication Process." Key Engineering Materials 287 (June 2005): 28–32. http://dx.doi.org/10.4028/www.scientific.net/kem.287.28.
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Si-based high-temperature ceramics are attractive materials for power microelectromechanical systems (power MEMS), such as microscale gas turbines, micro-combustors and micro-reactors. This presentation introduces a novel process for the microfabrication of Si3N4 ceramics, which mainly consists of pre-sintering of Si powder compacts, micromachining of pre-sintered Si preforms and reaction sintering of the micromachined Si preforms. The present process has its high potential for Si3N4 3-dimensional microfabrication because it combines the machinablity of pre-sintered Si powder compacts and near-net shaping characteristic of S3N4 reaction sintering. Si3N4 micro-components such as micro nozzle arrays and micro-rotor were fabricated by using the present process.
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KIM, JAE-HYUN, HAK-JOO LEE, SEUNG-WOO HAN, JUNG-YUP KIM, JUNG-SIL KIM, JAE-YOON KANG, SUNG-HOON CHOA, and CHANG-SEUNG LEE. "MECHANICAL BEHAVIOR OF FREESTANDING Mo THIN FILMS FOR RF–MEMS DEVICES." International Journal of Modern Physics B 20, no. 25n27 (October 30, 2006): 3757–62. http://dx.doi.org/10.1142/s0217979206040325.
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Radio frequency microelectromechanical systems (RF–MEMS) are an attractive solution for wireless telecommunication applications. Freestanding films play an important role in RF–MEMS devices. For the successful commercialization of RF–MEMS devices, however, it is necessary to evaluate the mechanical reliability of freestanding films. The first step in the evaluation is to characterize the mechanical behavior of the films. This study focuses on freestanding Mo thin films. Mo test structures with a thickness of 960 nm were fabricated using sputtering deposition and patterned using a surface and bulk micromachining process. The strip-bending test was used to measure the stress–strain relation of the freestanding Mo thin films. The measured elastic modulus, initial stress, and yield strength of Mo thin films are reported.
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Nanver, Lis K., Tihomir Knezevic, Xingyu Liu, Shivakumar D. Thammaiah, and Max Krakers. "On the Many Applications of Nanometer-Thin Pure Boron Layers in IC and Microelectromechanical Systems Technology." Journal of Nanoscience and Nanotechnology 21, no. 4 (April 1, 2021): 2472–82. http://dx.doi.org/10.1166/jnn.2021.19112.
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An overview is given of the many applications that nm-thin pure boron (PureB) layers can have when deposited on semiconductors such as Si, Ge, and GaN. The application that has been researched in most detail is the fabrication of nm-shallow p+n-like Si diode junctions that are both electrically and chemically very robust. They are presently used commercially in photodiode detectors for extremeultraviolet (EUV) lithography and scanning-electron-microscopy (SEM) systems. By using chemicalvapor deposition (CVD) or molecular beam epitaxy (MBE) to deposit the B, PureB diodes have been fabricated at temperatures from an optimal 700 °C to as low as 50 °C, making them both front- and back-end-of-line CMOS compatible. On Ge, near-ideal p+n-like diodes were fabricated by covering a wetting layer of Ga with a PureB capping layer (PureGaB). For GaN high electron mobility transistors (HEMTs), an Al-on-PureB gate stack was developed that promises to be a robust alternative to the conventional Ni-Au gates. In MEMS processing, PureB is a resilient nm-thin masking layer for Si micromachining with tetramethyl ammonium hydroxide (TMAH) or potassium hydroxide (KOH), and low-stress PureB membranes have also been demonstrated.
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Droogendijk, H., M. J. de Boer, R. G. P. Sanders, and G. J. M. Krijnen. "A biomimetic accelerometer inspired by the cricket's clavate hair." Journal of The Royal Society Interface 11, no. 97 (August 6, 2014): 20140438. http://dx.doi.org/10.1098/rsif.2014.0438.
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Crickets use so-called clavate hairs to sense (gravitational) acceleration to obtain information on their orientation. Inspired by this clavate hair system, a one-axis biomimetic accelerometer has been developed and fabricated using surface micromachining and SU-8 lithography. An analytical model is presented for the design of the accelerometer, and guidelines are derived to reduce responsivity due to flow-induced contributions to the accelerometer's output. Measurements show that this microelectromechanical systems (MEMS) hair-based accelerometer has a resonance frequency of 320 Hz, a detection threshold of 0.10 ms −2 and a dynamic range of more than 35 dB. The accelerometer exhibits a clear directional response to external accelerations and a low responsivity to airflow. Further, the accelerometer's physical limits with respect to noise levels are addressed and the possibility for short-term adaptation of the sensor to the environment is discussed.
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Sano, Chikako, Manabu Ataka, Gen Hashiguchi, and Hiroshi Toshiyoshi. "An Electret-Augmented Low-Voltage MEMS Electrostatic Out-of-Plane Actuator for Acoustic Transducer Applications." Micromachines 11, no. 3 (March 4, 2020): 267. http://dx.doi.org/10.3390/mi11030267.
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Despite the development of energy-efficient devices in various applications, microelectromechanical system (MEMS) electrostatic actuators yet require high voltages to generate large displacements. In this respect, electrets exhibiting quasi-permanent electrical charges allow large fixed voltages to be integrated directly within electrode structures to reduce or eliminate the need of DC bias electronics. For verification, a − 40 V biased electret layer was fabricated at the inner surface of a silicon on insulator (SOI) structure facing a 2 μm gap owing to the high compatibility of silicon micromachining and the potassium-ion-electret fabrication method. A − 10 V electret-augmented actuator with an out-of-plane motion membrane reached a sound pressure level (SPL) of 50 dB maximum with AC input voltage of V i n = 5 V pp alone, indicating a potential for acoustic transducer usage such as microspeakers. Such devices with electret biasing require only the input signal voltage, thus contributing to reducing the overall power consumption of the device system.
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Shetty, A., and G. Srinivasan. "MICROFABRICATED ORAL DRUG DELIVERY SYSTEMS." INDIAN DRUGS 52, no. 11 (November 28, 2015): 5–13. http://dx.doi.org/10.53879/id.52.11.10393.
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Microfabrication is a collection of techniques developed to fabricate micron sized features, best suited to develop the novel drug delivery microdevices. microfabrication techniques were originally developed in the microelectronics industry to produce functional devices on the micron scale such as sensors, switches, filters and gears. Approaches like modification of drug itself to improve its permeability/ solubility characters, encapsulation techniques using micro/nanoparticles, use of protease inhibitors to curb proteolytic degradation, and use of intelligent polymers and hydrogels do not offer a complete solution for adequate and safe delivery of drugs, vaccines, peptides, proteins and others. This technology has been applied to the successful fabrication of a variety of implantable and oral drug delivery devices based on silicon, glass, silicone elastomer or plastic materials. These techniques that are utilized at present have developed as a result of integrated circuit manufacturing technologies, such as photolithography, thin film growth/deposition, etching and bonding. Micromachining allows for control over surface features, aspect ratio, particle size, shape and facilitating the development of an engineered particle for drug delivery that can incorporate the advantages of microparticles while avoiding their design flaws. It helps in multi-cell and multi-site attachment, multiple reservoirs of desired size to contain multiple drugs/biomolecules of interest. These fabrication techniques have led to the development of microelectromechanical systems (MEMS), bioMEMS, micro-total analysis systems (μ-TAS), lab-on-a-chip and other microdevices. Microfabricated devices are designed for uni-directional release, to prevent enzyme degradation, precise dosing and better patient compliance. Drug delivery in the form of microparticles and micropatches have been used for targeted delivery as well as in treatment of diseases like diabetes and cancer.
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Ben Messaoud, Jaweb, Jean-François Michaud, Dominique Certon, Massimo Camarda, Nicolò Piluso, Laurent Colin, Flavien Barcella, and Daniel Alquier. "Investigation of the Young’s Modulus and the Residual Stress of 4H-SiC Circular Membranes on 4H-SiC Substrates." Micromachines 10, no. 12 (November 21, 2019): 801. http://dx.doi.org/10.3390/mi10120801.
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The stress state is a crucial parameter for the design of innovative microelectromechanical systems based on silicon carbide (SiC) material. Hence, mechanical properties of such structures highly depend on the fabrication process. Despite significant progresses in thin-film growth and fabrication process, monitoring the strain of the suspended SiC thin-films is still challenging. However, 3C-SiC membranes on silicon (Si) substrates have been demonstrated, but due to the low quality of the SiC/Si heteroepitaxy, high levels of residual strains were always observed. In order to achieve promising self-standing films with low residual stress, an alternative micromachining technique based on electrochemical etching of high quality homoepitaxy 4H-SiC layers was evaluated. This work is dedicated to the determination of their mechanical properties and more specifically, to the characterization of a 4H-SiC freestanding film with a circular shape. An inverse problem method was implemented, where experimental results obtained from bulge test are fitted with theoretical static load-deflection curves of the stressed membrane. To assess data validity, the dynamic behavior of the membrane was also investigated: Experimentally, by means of laser Doppler vibrometry (LDV) and theoretically, by means of finite element computations. The two methods provided very similar results since one obtained a Young’s modulus of 410 GPa and a residual stress value of 41 MPa from bulge test against 400 GPa and 30 MPa for the LDV analysis. The determined Young’s modulus is in good agreement with literature values. Moreover, residual stress values demonstrate that the fabrication of low-stressed SiC films is achievable thanks to the micromachining process developed.
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Chang, Yunxia, Qichang Zhang, Wei Wang, and Jianxin Han. "Mechanical Behaviors of Electrostatic Microbeams with Nonideal Supports." Shock and Vibration 2020 (August 17, 2020): 1–18. http://dx.doi.org/10.1155/2020/4507280.
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Deviation of the actual system from the ideal supporting conditions caused by micromachining errors and manufacturing defects or the requirement of innovative design and optimization of microelectromechanical systems (MEMS) make the nonideal boundary in the micro-/nanoresonator system receive wide attention. In this paper, we consider the neutral plane tension, fringing field, and nonideal boundary factors to establish a continuum model of electrostatically driven microbeam resonators. The convergent static solution with nine-order Galerkin decomposition is calculated. Then, based on the static solution, a 1-DOF dynamic equation of up to the fifth-order of the dynamic displacement using a Taylor expansion is derived. The method of multiple scales is used to study the effect of spring stiffness coefficients on the primary frequency response characteristics and hardening-softening conversion phenomena in four cases. The various law of the system’s static and dynamic performances with the spring stiffness coefficients is obtained. The conditions for judging the hardening-softening transition are derived. So, adjusting the support stiffness values can be a measure of optimizing the resonator performance.
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Maboudian, Roya. "Adhesion and Friction Issues Associated With Reliable Operation of MEMS." MRS Bulletin 23, no. 6 (June 1998): 47–51. http://dx.doi.org/10.1557/s0883769400030633.
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A growing interest exists in developing technologies that use silicon and other electronic materials as mechanical materials. Using standard processes of the integrated-circuit industry, researchers have successfully fabricated miniature mechanical components (micromachines) such as membranes, gears, motors, pumps, and valves. The integration of miniaturized mechanical components with microelectronic components has spawned a new technology known as microelectromechanical systems (MEMS). It promises to extend the benefits of microelectronic fabrication to sensing and actuating functions. Early applications of this technology include the digital mirror display, which has of the order of 106 aluminum thin-film micromirrors fabricated on top of a complementary-metal-oxide-semiconductor static random-access-memory integrated circuit. Other applications include integrated accelerometers for tasks such as air-bag deployment.A number of fabrication techniques have been developed for this technology and have been reviewed elsewhere. In this review, I focus on surface-micromachining technology and adhesion and friction problems in surface-micromachined polycrystalline silicon (polysilicon) structures, though many of the principles discussed will also apply both to single-crystalline silicon and nonsilicon-based structures. Surface micromachining, defined as the fabrication of micromechanical structures from deposited thin films, is one of the core technological processes underlying MEMS. Surface microstructures have lateral dimensions of 50-500 μm with thicknesses of 0.1–2.5 μm and are offset 0.1–2 μm from the substrate. The basic steps in a surface-micromachining process appear in Figure 1. First the substrate is typically coated with an isolation layer (Figure la) that protects it during subsequent etching steps. A sacrificial layer is then deposited on the substrate and patterned. For simplicity, Figure 1b shows that the opening of the sacrificial layer is terminated on the isolation layer. The microstructural thin film is then deposited and etched (Figure 1c). Finally selective etching of the sacrificial layer creates the freestanding micromechanical structures such as the cantilever beam shown in cross section in Figure 1d. The technique can be extended to make multiple-layer microstructures.
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Ge, Chang, and Edmond Cretu. "A Polymeric Piezoelectric Tactile Sensor Fabricated by 3D Printing and Laser Micromachining for Hardness Differentiation during Palpation." Micromachines 13, no. 12 (December 7, 2022): 2164. http://dx.doi.org/10.3390/mi13122164.
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Tactile sensors are important bionic microelectromechanical systems that are used to implement an artificial sense of touch for medical electronics. Compared with the natural sense of touch, this artificial sense of touch provides more quantitative information, augmenting the objective aspects of several medical operations, such as palpation-based diagnosis. Tactile sensors can be effectively used for hardness differentiation during the palpation process. Since palpation requires direct physical contact with patients, medical safety concerns are alleviated if the sensors used can be made disposable. In this respect, the low-cost, rapid fabrication of tactile sensors based on polymers is a possible alternative. The present work uses the 3D printing of elastic resins and the laser micromachining of piezoelectric polymeric films to make a low-cost tactile sensor for hardness differentiation through palpation. The fabricated tactile sensor has a sensitivity of 1.52 V/mm to mechanical deformation at the vertical direction, a sensitivity of 11.72 mV/HA in sensing material hardness with a pressing depth of 500 µm for palpation, and a validated capability to detect rigid objects buried in a soft tissue phantom. Its performance is comparable with existing piezoelectric tactile sensors for similar applications. In addition, the tactile sensor has the additional advantage of providing a simpler microfabrication process.
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Bai, Yufang, Jie Zeng, Jiwei Huang, Shaolong Zhong, Zhuming Cheng, and Dakai Liang. "Measurement of Structural Loads Using a Novel MEMS Extrinsic Fabry–Perot Strain Sensor." Applied Sciences 10, no. 1 (December 18, 2019): 18. http://dx.doi.org/10.3390/app10010018.
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In this paper, microelectromechanical systems (MEMS) technology was used to fabricate a novel extrinsic fiber Fabry–Perot (EFFP) strain sensor; this fiber sensor is applied to measure load with higher precision for a small structure. The sensor cavity consists of two Fabry–Perot (FP) cavity mirrors that are processed by surface micromachining and then fused and spliced together by the silicon–glass anode bonding process. The initial cavity length can be strictly controlled, and the excellent parallelism of the two faces of the cavity results in a high interference fineness. Then, the anti-reflection coating process is applied to the sensor to improve the clarity of the interference signal with the cavity, with its wavelength working within the range of the C + L band. Next, the sensor placement is determined by the finite element software Nastran. Experimental results indicate that the sensor exhibits a good linear response (99.77%) to load changes and a high repeatability. Considering the strain transfer coefficient, the sensitivity for the tested structure load is as high as 35.6 pm/N. Due to the miniaturization, repeatability, and easy-to-batch production, the proposed sensor can be used as a reliable and practical force sensor.
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Bajwa, Rayan, and Murat Kaya Yapici. "Integrated On-Chip Transformers: Recent Progress in the Design, Layout, Modeling and Fabrication." Sensors 19, no. 16 (August 13, 2019): 3535. http://dx.doi.org/10.3390/s19163535.
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On-chip transformers are considered to be the primary components in many RF wireless applications. This paper provides an in-depth review of on-chip transformers, starting with a presentation on the various equivalent circuit models to represent transformer behavior and characterize their performance. Next, a comparative study on the different design and layout strategies is provided, and the fabrication techniques for on-chip implementation of transformers are discussed. The critical performance parameters to characterize on-chip transformers, such as the Q-factor, coupling factor (k), resonance frequency (fSR), and others, are discussed with reference to trade-offs in silicon chip real-estate. The performance parameters and area requirements for different types of on-chip transformers are summarized in tabular form and compared. Several techniques for performance enhancement of on-chip transformers, including the different types of micromachining and integration approaches stemming from MEMS (microelectromechanical systems) technologies are also analyzed. Lastly, the different uses and applications of on-chip transformers are discussed to highlight the evolution of on-chip transformer technology over the recent years and provide directions for future work in this field.
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Kim, Jong Jin, Dong Il Son, and Dong Il Kwon. "Analysis of Time-Dependent Degradation of a Micro-Resonating Structure with a Notch." Key Engineering Materials 297-300 (November 2005): 594–602. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.594.
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Reliability is very important for the further development, commercialization and miniaturization of microelectromechanical systems (MEMS). In particular, concern arises about time-dependent degradation such as fatigue for MEMS with flexural elements because they are used in cyclic loading. This study investigated the time-dependent degradation of silicon micro-resonating structures. The test structure, designed and fabricated by micromachining, consisted of suspended beams, shuttle, combs and electrodes. It was operated at resonance mode by applying AC voltage with a function generator and the change of resonant frequency was detected. The failure of a notched beam was detected by the saturation of the decrease in resonant frequency. The test structure showed a decrease in resonant frequency with cycles that was attributed to stiffness degradation due to fatigue crack growth at the notch tip. By analyzing the test structure as a spring-mass system, the variation of stiffness of a notched beam with cycles was obtained from the resonant frequency. From this relation and the stiffness-crack relation, crack growth with cycles was calculated. Finally, the lifetime of the test structure was calculated and compared with experimental results.
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Kumar, A. Sravan, Sankha Deb, and S. Paul. "Burr removal from high-aspect-ratio micro-pillars using ultrasonic-assisted abrasive micro-deburring." Journal of Micromechanics and Microengineering 32, no. 5 (April 19, 2022): 055010. http://dx.doi.org/10.1088/1361-6439/ac6562.
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Abstract The demand for high-aspect-ratio microstructures is ever increasing in the fields of microelectromechanical systems, biomedicine, aerospace, telecommunication, and heat transfer. Mechanical micromachining processes have a distinct advantage over lithography-based processes for machining complex three-dimensional microstructures on a variety of materials with high accuracy and surface finish. But the tool-based micromachining operations face inherent issues in the form of excessive burr formation, which needs to be addressed by post-machining burr removal operations. In this study, an ultrasonic-assisted abrasive micro-deburring process employing a probe sonotrode and abrasive particles has been investigated for deburring high-aspect-ratio micro-pillars machined on aluminium 6061 and copper. Deburring of micromilled pillars of aspect ratio 5:1 has been achieved while maintaining pillar integrity. The mechanism of deburring has been observed to be mainly by the impact of the abrasive particles with a minor role played by liquid cavitation. Burr reduction as high as 88.75% for Al 6061 and 90.1% for copper has been achieved in a short processing time of 10 s. This is a significantly faster process than other ultrasonic cavitation-based deburring processes described in literature (deburring time ranging from 60 min to a few hours). With proper control of the process parameters like stand-off distance and power, burr removal has been achieved while maintaining the integrity of the micro-pillars. Pure water cavitation has also been studied for comparison, which has resulted in a burr removal by 51.5% and 53.1% for Al 6061 and copper, respectively. Upon proper selection of the process parameters, this process can be a viable alternative to existing deburring methods in terms of minimal processing time and structure damage.
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Acevedo-Mijangos, Jesús, Antonio Ramírez-Treviño, Daniel A. May-Arrioja, Patrick LiKamWa, Héctor Vázquez-Leal, and Agustín L. Herrera-May. "Design and fabrication of a microelectromechanical system resonator based on two orthogonal silicon beams with integrated mirror for monitoring in-plane magnetic field." Advances in Mechanical Engineering 11, no. 7 (July 2019): 168781401985368. http://dx.doi.org/10.1177/1687814019853683.
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We present a resonant magnetic field sensor based on microelectromechanical systems technology with optical detection. The sensor has single resonator composed of two orthogonal silicon beams (600 µm × 26 µm × 2 µm) with an integrated mirror (50 µm × 34 µm × 0.11 µm) and gold tracks (16 µm × 0.11 µm). The resonator is fabricated using silicon-on-insulator wafer in a simple bulk micromachining process. The sensor has easy performance that allows its oscillation in the first bending vibration mode through the Lorentz force for monitoring in-plane magnetic field. Analytical models are developed to predict first bending resonant frequency, quality factor, and displacements of the resonator. In addition, finite element method models are obtained to estimate the resonator performance. The results of the proposed analytical models agree well with those of the finite element method models. For alternating electrical current of 30 mA, the sensor has a theoretical linear response, a first bending resonant frequency of 43.8 kHz, a sensitivity of 46.1 µm T−1, and a power consumption close to 54 mW. The experimental resonant frequency of the sensor is 53 kHz. The proposed sensor could be used for monitoring in-plane magnetic field without a complex signal conditioning system.
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Li, Jiachen, Jun Liu, Chunrong Peng, Xiangming Liu, Zhengwei Wu, and Fengjie Zheng. "Design and Testing of a Non-Contact MEMS Voltage Sensor Based on Single-Crystal Silicon Piezoresistive Effect." Micromachines 13, no. 4 (April 15, 2022): 619. http://dx.doi.org/10.3390/mi13040619.
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The paper presents a novel non-contact microelectromechanical systems (MEMS) voltage sensor based on the piezoresistive effect of single-crystal silicon. The novelty of the proposed sensor design lies in the implementation of unique single-crystal silicon piezoresistive beams for voltage measurement. The sensitive structure of the sensor produces electrostatic force deformation due to the measured voltage, resulting in the resistance change of single-crystal silicon piezoresistive beams which support a vibrating diaphragm. The voltage can be measured by sensing the resistance change. Moreover, the sensor does not need an additional driving signal and has lower power consumption. The prototype of the sensor was fabricated using an SOI micromachining process. The piezoresistive characteristics of the sensor and the corresponding output response relationship were analyzed through theoretical analysis and finite element simulation. The voltage response characteristics of the sensor were achieved at power frequencies from 50 Hz to 1000 Hz in the paper. The experimental results showed that they were in good agreement with simulations results with the theoretical model and obtained good response characteristics. The sensor has demonstrated that the minimum detectable voltages were 1 V for AC voltages at frequencies from 50 Hz to 300 Hz and 0.5 V for AC voltages at frequencies from 400 Hz to 1000 Hz, respectively. Moreover, the linearities of the sensor were 3.4% and 0.93% in the voltage measurement range of 900–1200 V at the power frequency of 50 Hz and in the voltage measurement range of 400–1200 V at the frequency of 200 Hz, respectively.
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Schoeman, Johan, and Monuko du Plessis. "A two-port electrothermal model for suspended MEMS device structures with multiple inputs." Journal of Sensors and Sensor Systems 8, no. 2 (October 9, 2019): 293–304. http://dx.doi.org/10.5194/jsss-8-293-2019.
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Abstract. Advances in micromachining have led to the development of microelectromechanical systems (MEMS) devices with suspended structures used in a variety of sensors. Of note for this work are sensor types where two elements exist on the suspended membrane, including examples like air flow and differential pressure detectors, gas detection, and differential scanning calorimetry sensors. Intuitively one would argue that some thermal loss exists between the two elements. However, surprisingly little is documented about this electrothermal interaction. The work presented here addresses this shortcoming by defining a new parameter set, a matrix of thermal coupling coefficients. They are used within our novel two-port electrothermal model based on the heat flow equation adapted as a linear system of equations. However, the model is only effective with knowledge of these coefficients. We introduce an approach to extract the coefficients using finite-element method (FEM)-based multiphysics simulation tools and revisit and extend our previous method of non-ideal power coupling, this time to extract the coefficient matrix from measured data. Both specialist simulation tools and device manufacturing are very expensive. However, they are the only choices in the absence of an analytic model. A major contribution of this work is the derivation of a model to predict the coefficients by analytic means from the device dimensions and material properties. The research contribution and paper culminate in a comparison of analytic, simulated, and experimentally extracted values of two different devices to verify and demonstrate the effectiveness of the proposed models. The values compare well and show that the best results achieved are approximately 90 % and 70 % thermal linkage respectively for vacuum and atmospheric pressure conditions.
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Kumar, Shashi, Pradeep Kumar Rathore, Brishbhan Singh Panwar, and Jamil Akhtar. "Development of a current mirror-integrated pressure sensor using CMOS-MEMS cofabrication techniques." Microelectronics International 35, no. 4 (October 1, 2018): 203–10. http://dx.doi.org/10.1108/mi-05-2017-0022.
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Purpose This paper aims to describe the fabrication and characterization of current mirror-integrated microelectromechanical systems (MEMS)-based pressure sensor. Design/methodology/approach The integrated pressure-sensing structure consists of three identical 100-µm long and 500-µm wide n-channel MOSFETs connected in a resistive loaded current mirror configuration. The input transistor of the mirror acts as a constant current source MOSFET and the output transistors are the stress sensing MOSFETs embedded near the fixed edge and at the center of a square silicon diaphragm to sense tensile and compressive stresses, respectively, developed under applied pressure. The current mirror circuit was fabricated using standard polysilicon gate complementary metal oxide semiconductor (CMOS) technology on the front side of the silicon wafer and the flexible pressure sensing square silicon diaphragm, with a length of 1,050 µm and width of 88 µm, was formed by bulk micromachining process using tetramethylammonium hydroxide solution on the backside of the wafer. The pressure is monitored by the acquisition of drain voltages of the pressure sensing MOSFETs placed near the fixed edge and at the center of the diaphragm. Findings The current mirror-integrated pressure sensor was successfully fabricated and tested using in-house developed pressure measurement system. The pressure sensitivity of the tested sensor was found to be approximately 0.3 mV/psi (or 44.6 mV/MPa) for pressure range of 0 to 100 psi. In addition, the pressure sensor was also simulated using Intellisuite MEMS Software and simulated pressure sensitivity of the sensor was found to be approximately 53.6 mV/MPa. The simulated and measured pressure sensitivities of the pressure sensor are in close agreement. Originality/value The work reported in this paper validates the use of MOSFETs connected in current mirror configuration for the measurement of tensile and compressive stresses developed in a silicon diaphragm under applied pressure. This current mirror readout circuitry integrated with MEMS pressure-sensing structure is new and fully compatible to standard CMOS processes and has a promising application in the development CMOS-MEMS-integrated smart sensors.
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Chu, V., J. Gaspar, and J. P. Conde. "Thin Film Microelectromechanical Systems." MRS Proceedings 715 (2002). http://dx.doi.org/10.1557/proc-715-a12.3.
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AbstractThis paper presents the fabrication and characterization of MEMS structures on glass substrates using thin film silicon technology and surface micromachining. The technology developed to process bridge and cantilever structures as well as the electromechanical characterization of these structures is discussed. This technology can enable the expansion of MEMS to applications requiring large area and/or flexible substrates. The main results for the characterization of the movement of the structures are as follows: (1) in the quasi-DC regime and at low applied voltages, the response is linear with the applied dc voltage. Using an electromechanical model which takes into account the constituent materials and geometry of the bilayer, it is possible to extract the deflection of the structures. This estimate suggests that it is possible to control the actuation of these structures to deflections on the sub-nanometric scale; (2) resonance frequencies of up to 20 MHz have been measured on hydrogenated amorphous silicon (a-Si:H) bridge structures with quality factors (Q) of 70-100 in air. The frequency depends inversely on the square of the structure length, as predicted by the mechanical model; and (3) using an integrated permanent magnet/magnetic sensor system, it is possible to measure the structure movement on-chip and to obtain an absolute calibration of the deflection of the structures.
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Mehregany, Mehran, and Christian A. Zorman. "Micromachining Techniques for Advanced SiC MEMS." MRS Proceedings 640 (2000). http://dx.doi.org/10.1557/proc-640-h4.3.
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ABSTRACTThis paper reviews the development of a multilayer, micromolding-based surface micromachining process for SiC microelectromechanical systems (MEMS). The micromolding process uses polysilicon and SiO2 thin films that are deposited onto polysilicon and SiO2 sacrificial layers, patterned into micromolds by reactive ion etching, filled with polycrystalline SiC (poly-SiC), planarized by mechanical polishing, and eventually dissolved and released in selective wet chemical etchants. In addition, a SiC lift-off technique that exploits the microstructural differences between SiC films deposited on Si, SiO2 and Si3N4 surfaces has been developed. The micromolding and lift-off techniques are being used as the basic patterning processes for a four-layer, poly-SiC surface micromachining process that we call the MUSiC (Multi-User SiC) process.
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Sathyanarayanan, S., and A. Vimala Juliet. "Simulation of Low Pressure MEMS Sensor for Biomedical Application." Journal of Nanotechnology in Engineering and Medicine 2, no. 3 (August 1, 2011). http://dx.doi.org/10.1115/1.4004025.
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Micromachining technology has greatly benefited from the success of developments in implantable biomedical microdevices. In this paper, microelectromechanical systems (MEMS) capacitive pressure sensor operating for biomedical applications in the range of 20–400 mm Hg was designed. Employing the microelectromechanical systems technology, high sensor sensitivities and resolutions have been achieved. Capacitive sensing uses the diaphragm deformation-induced capacitance change. The sensor composed of a rectangular polysilicon diaphragm that deflects due to pressure applied over it. Applied pressure deflects the 2 µm diaphragm changing the capacitance between the polysilicon diaphragm and gold flat electrode deposited on a glass Pyrex substrate. The MEMS capacitive pressure sensor achieves good linearity and large operating pressure range. The static and thermo electromechanical analysis were performed. The finite element analysis data results were generated. The capacitive response of the sensor performed as expected according to the relationship of the spacing of the plates.
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Uppal, Nitin, and Panos S. Shiakolas. "Micromachining Characteristics of NiTi Based Shape Memory Alloy Using Femtosecond Laser." Journal of Manufacturing Science and Engineering 130, no. 3 (June 1, 2008). http://dx.doi.org/10.1115/1.2936380.
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Femtosecond laser micromachining (FLM) is a relatively new and promising technology for the micromachining of a wide spectrum of engineering materials with micron and submicron size features. The interaction mechanism of femtosecond laser pulses with matter is not the same as that found in traditional lasers. This manuscript presents a detailed study of the ablation characteristics of a nickel-titanium (NiTi) shape memory alloy in air with femtosecond laser pulses. The single- and multishot ablation threshold fluence and the incubation coefficient (predicting the extent to which accumulation could take place in a material) are evaluated. In addition, morphological changes, such as the emergence of a ripple pattern, are discussed along with the identification of gentle and strong ablation phases. This study provides for the understanding and characterization of NiTi micromachining using FLM technology, which could aid in the identification of new applications for smart materials in the macro-, nano-, and microelectromechanical system domains using this technology.
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Pal, Prem, and Kazuo Sato. "Advanced Wet Etch Bulk Micromachining in {100} Silicon Wafers." MRS Proceedings 1222 (2009). http://dx.doi.org/10.1557/proc-1222-dd05-04.
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AbstractIn this work we have developed novel microfabrication processes using wet anisotropic etchants to perform advanced bulk micromachining in {100}Si wafers for the realization of microelectromechanical systems (MEMS) structures with new shapes. The etching is performed in two steps in pure and Triton-X-100 [C14H22O(C2H4O)n, n = 9-10] added 25 wt% tetramethyl ammonium hydroxide (TMAH) solutions. The local oxidation of silicon (LOCOS) is attempted after the first anisotropic etching step in order to protect the exposed silicon. Two types of structures (fixed and freestanding) are fabricated. The fixed structures contain perfectly sharp corners and edges. Thermally grown silicon dioxide (SiO2) is used for the fabrication of freestanding structures. Present research is an approach to fabricate advanced MEMS structures, extending the range of 3D structures fabricated by silicon wet anisotropic etching.
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Namura, Moriaki, and Toshiyuki Toriyama. "Experimental Study on Aerodynamics of Microelectromechanical Systems Based Single-Crystal-Silicon Microscale Supersonic Nozzle." Journal of Fluids Engineering 135, no. 8 (May 23, 2013). http://dx.doi.org/10.1115/1.4024080.
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In this paper, the design, microfabrication, and direct measurement of the static pressure distribution for the aerodynamics of a single-crystal-silicon microscale supersonic nozzle are described. The microscale supersonic nozzle has a convergent–divergent section and a throat area of 100μm × 300μm. The microscale supersonic nozzle was fabricated by silicon bulk micromachining technology. The degree of the rarefaction of nozzle flow was determined by the Knudsen number (Kn). The operation envelope that determines whether the continuum or rarefied flow assumption is appropriate can be expressed as a function of Kn and related parameters. The effect of nonadiabatic operation on microscale nozzle flow was investigated on the basis of wall heat transfer. These physical correlations were taken into account for the classical Shapiro's equations to analyze the microscale nozzle flow aerodynamics (Shapiro, 1953, The Dynamics and Thermodynamics of Compressible Fluid Flow, Ronald, New York, Chap. 7,8; Greitzer et al., 2006, Internal Flow, Cambridge University, Cambridge, UK, Chap. 2,10). Furthermore, the solutions of Shapiro's equations were compared with the experimental results by the authors and other research institutions in order to demonstrate the validity of the proposed aerodynamics design concept for microscale continuum flow.
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Purohit, S., Veerla Swarnalatha, A. K. Pandey, RK Sharma, and Prem Pal. "Wet Bulk Micromachining Characteristics of Si{110} in NaOH-based solution." Journal of Micromechanics and Microengineering, October 19, 2022. http://dx.doi.org/10.1088/1361-6439/ac9b64.
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Abstract Silicon wet bulk micromachining is an extensively used technique in microelectromechanical systems (MEMS) to fabricate variety of microstructures. It utilizes low-cost etchants and suitable for batch process that made it popular for industrial production. The etch rate and the undercutting at convex corner significantly affect the productivity. In wet anisotropic etching-based micromachining, Si{110} wafer is employed to fabricate unique shape geometries such as the microstructures with vertical sidewalls. In this research, we have investigated the etching characteristics of Si{110} in 10M sodium hydroxide (NaOH) without and with addition of NH2OH. The main objective of the present work is to improve the etch rate and the undercutting at convex corners. Average surface roughness (Ra), etch depth, and undercutting length are measured using a 3D scanning laser microscope. Surface morphology of the etched Si{110} surface is examined using a scanning electron microscope (SEM). The incorporation of NH2OH significantly improves the etch rate and the corner undercutting, which are useful to enhance the productivity. Additionally, the effect of etchant age on the etch rate and other etching characteristics are investigated. The etch rate of silicon and the undercutting at convex corners decrease with etchant aging. The results presented in this paper are very useful to scientists and engineers who use silicon wet anisotropic etching to fabricate MEMS structures using bulk micromachining. Moreover, it has great potential to promote the application of wet etching in MEMS.
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Wood, R. J., S. Avadhanula, R. Sahai, E. Steltz, and R. S. Fearing. "Microrobot Design Using Fiber Reinforced Composites." Journal of Mechanical Design 130, no. 5 (March 26, 2008). http://dx.doi.org/10.1115/1.2885509.
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Mobile microrobots with characteristic dimensions on the order of 1cm are difficult to design using either microelectromechanical systems technology or precision machining. This is due to the challenges associated with constructing the high strength links and high-speed, low-loss joints with micron scale features required for such systems. Here, we present an entirely new framework for creating microrobots, which makes novel use of composite materials. This framework includes a new fabrication process termed smart composite microstructures (SCM) for integrating rigid links and large angle flexure joints through a laser micromachining and lamination process. We also present solutions to actuation and integrated wiring issues at this scale using SCM. Along with simple design rules that are customized for this process, our new complete microrobotic framework is a cheaper, quicker, and altogether superior method for creating microrobots that we hope will become the paradigm for robots at this scale.
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Purohit, S., V. Swarnalatha, A. K. Pandey, and P. Pal. "Wet anisotropic etching characteristics of Si{111} in NaOH-based solution for silicon bulk micromachining." Micro and Nano Systems Letters 10, no. 1 (December 1, 2022). http://dx.doi.org/10.1186/s40486-022-00162-7.
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AbstractSilicon bulk micromachining is extensively employed method in microelectromechanical systems (MEMS) for the formation of freestanding (e.g., cantilevers) and fixed (e.g., cavities) microstructures. Wet anisotropic etching is a popular technique to perform silicon micromachining as it is low-cost, scalable, and suitable for large scale batch processing, which are the major factors considered in the industry to reduce the cost of the product. In this work, we report the wet anisotropic etching characteristics of Si{111} in sodium hydroxide (NaOH) without and with addition of hydroxylamine (NH2OH). 10M NaOH and 12% NH2OH are used for this study. The effect of NH2OH is investigated on the etch rate, etched surface roughness and morphology, and the undercutting at mask edges aligned along < 112 > direction. These are the major etching characteristics, which should be studied in a wet anisotropic etchant. A 3D laser scanning microscope is utilized to measure the surface roughness, etch depth, and undercutting length, while the etched surface morphology is examined using a scanning electron microscope (SEM). The incorporation of NH2OH in NaOH significantly enhances the etch rate and the undercutting at the mask edges that do not consist of {111} planes. To fabricate freestanding structure (e.g., microcantilever) on Si{111} wafer, high undercutting at < 112 > mask edges is desirable to reduce the release time. Moreover, the effect of etchant age on the abovementioned etching characteristics are investigated. The etch rate and undercutting reduce significantly with the age of the modified NaOH. The present paper reports very interesting results for the applications in wet bulk micromachining of Si{111}.
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Cao, Zhiqiang, Tong-Yi Zhang, and Xin Zhang. "Microbridge Nanoindentation Testing of Plasma-Enhanced Chemical Vapor Deposited Silicon Oxide Films." MRS Proceedings 841 (2004). http://dx.doi.org/10.1557/proc-841-r12.4.
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ABSTRACTPlasma-enhanced chemical vapor deposited (PECVD) silane-based oxides (SiOx) have been widely used in both microelectronics and MEMS (MicroElectroMechanical Systems) to form electrical and/or mechanical components. In this paper, a novel nanoindentation-based microbridge testing method is developed to measure both the residual stresses and Young's modulus of PECVD SiOx films. Our theoretical model employed a closed formula of deflection vs. load, considering both substrate deformation and the residual stresses in the thin films. In particular, the non-negligible residual deflection caused by excessive compressive stresses was taken into account. Freestanding microbridges made of PECVD SiOx films were fabricated using bulk micromachining techniques. To simulate the thermal processing in device fabrication, these microbridges were subjected to rapid thermal annealing (RTA) up to 800°C. A microstructure-based mechanism was applied to explain the experimental results of the residual stress changes in PECVD SiOx films after thermal annealing.
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Neves, Hercules P., Thomas D. Kudrle, Jia-Ming Chen, Scott G. Adams, Michel Maharbiz, Sergey Lopatin, and N. C. MacDonald. "Conformal Electroless Copper and Nickel Deposition on Mems Structures." MRS Proceedings 546 (1998). http://dx.doi.org/10.1557/proc-546-139.
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AbstractWe propose electroless metallization as a method for conformal metal deposition microelectromechanical systems (MEMS). The intrinsically conformal nature of electroless deposition makes it ideal for coating high aspect ratio (greater than 50:1) structures frequently fabricated with micromachining techniques We take advantage of the selective nature of the deposition to obtain self-aligned electrical isolation. We minimize the metal film roughness for potential applications in RF and optics. Given the specific MEMS metallization requirements, we determined the ideal concentrations of additives and surfactants in order to provide good electrical isolation, low roughness and high film reliability. Our depositions were done using seed layers as well as through direct chemical activation of the silicon surface. Characteristics such as resistivity [ 1 ], morphology [ 1 ], microstructure [ 2 ], and electrochemical behavior [ 3 ] have already been reported in the literature; our paper is focused on the specific requirements for MEMS applications.
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Hopkins, Patrick E., and Leslie M. Phinney. "Thermal Conductivity Measurements on Polycrystalline Silicon Microbridges Using the 3ω Technique." Journal of Heat Transfer 131, no. 4 (February 11, 2009). http://dx.doi.org/10.1115/1.3072907.
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The thermal performance of microelectromechanical systems devices is governed by the structure and composition of the constituent materials as well as the geometrical design. With the continued reduction in the characteristic sizes of these devices, experimental determination of the thermal properties becomes more difficult. In this study, the thermal conductivity of polycrystalline silicon (polysilicon) microbridges are measured with the transient 3ω technique and compared with measurements on the same structures using a steady state Joule heating technique. The microbridges with lengths from 200 μm to 500 μm were designed and fabricated using the Sandia National Laboratories SUMMiT V™ surface micromachining process. The advantages and disadvantages of the two experimental methods are examined for suspended microbridge geometries. The differences between the two measurements, which arise from the geometry of the test structures and electrical contacts, are explained by bond pad heating and thermal resistance effects.
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Abidin, Ummikalsom, Burhanuddin Yeop Majlis, and Jumril Yunas. "FABRICATION OF PYRAMIDAL CAVITY STRUCTURE WITH MICRON-SIZED TIP USING ANISOTROPIC KOH ETCHING OF SILICON (100)." Jurnal Teknologi 74, no. 10 (June 21, 2015). http://dx.doi.org/10.11113/jt.v74.4846.
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Microelectromechanical System (MEMS) are systems of micron-sized structures and typically integrated with microelectronic components. Bulk micromachining using wet anisotropic etching is able to etch silicon substrates to a desired three-dimensional (3D) structure, depending on the silicon crystallographic orientation. To date, MEMS components i.e. thermal, pressure, mechanical, bio/chemical sensors have been fabricated with wet anisotropic etching of silicon. This paper presents the fabrication of a 3D pyramidal cavity structure with micron-sized tip of silicon (100) using anisotropic KOH etching of w/w 45 % at 80 oC temperature. Volume percent of 10 % IPA as a less polar diluent is added to the KOH etching solution in saturating the solution and controlling the etching selectivity and rate. Smooth etched silicon surface of hillock free is able to be achieved with IPA addition to the KOH etching solution. A characteristic V-shaped cavity with side angle of 54.8 degrees has successfully been formed and is almost identical to the theoretical structure model. Comparison of two different silicon nitride window masks on the micron-size tip formation is also investigated. Under etch, over etch and etching selectivity, as common problems effecting the micron-tip size variation, are also addressed in this work. In conclusion, anisotropic KOH etching as a simple, fast and inexpensive bulk micromachining technique, in fabricating 3D MEMS structure using silicon (100), is validated in this work.
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Pal, Prem, Veerla Swarnalatha, Avvaru Venkata Narasimha Rao, Ashok Kumar Pandey, Hiroshi Tanaka, and Kazuo Sato. "High speed silicon wet anisotropic etching for applications in bulk micromachining: a review." Micro and Nano Systems Letters 9, no. 1 (February 22, 2021). http://dx.doi.org/10.1186/s40486-021-00129-0.
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AbstractWet anisotropic etching is extensively employed in silicon bulk micromachining to fabricate microstructures for various applications in the field of microelectromechanical systems (MEMS). In addition, it is most widely used for surface texturing to minimize the reflectance of light to improve the efficiency of crystalline silicon solar cells. In wet bulk micromachining, the etch rate is a major factor that affects the throughput. Slower etch rate increases the fabrication time and therefore is of great concern in MEMS industry where wet anisotropic etching is employed to perform the silicon bulk micromachining, especially to fabricate deep cavities and freestanding microstructures by removal of underneath material through undercutting process. Several methods have been proposed to increase the etch rate of silicon in wet anisotropic etchants either by physical means (e.g. agitation, microwave irradiation) or chemically by incorporation of additives. The ultrasonic agitation during etching and microwave irradiation on the etchants increase the etch rate. However, ultrasonic method may rupture the fragile structures and microwave irradiation causes irradiation damage to the structures. Another method is to increase the etching temperature towards the boiling point of the etchant. The etching characteristics of pure potassium hydroxide solution (KOH) is studied near the boiling point of KOH, while surfactant added tetramethylammonium hydroxide (TMAH) is investigated at higher temperature to increase the etch rate. Both these studies have shown a potential way of increasing the etch rate by elevating the temperature of the etchants to its boiling point, which is a function of concentration of etch solution. The effect of various kinds of additives on the etch rate of silicon is investigated in TMAH and KOH. In this paper, the additives which improve the etch rate have been discussed. Recently the effect of hydroxylamine (NH2OH) on the etching characteristics of TMAH and KOH is investigated in detail. The concentration of NH2OH in TMAH/KOH is varied to optimize the etchant composition to obtain improved etching characteristics especially the etch rate and undercutting which are important parameters for increasing throughput. In this article, different methods explored to improve the etch rate of silicon have been discussed so that the researchers/scientists/engineers can get the details of these methods in a single reference.
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Sedky, Sherif. "Electrical Properties and Noise of Poly SiGe Deposited at Temperatures Compatible With MEMS Integration on Top of Standard CMOS." MRS Proceedings 729 (2002). http://dx.doi.org/10.1557/proc-729-u3.2.
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The rapid development of MicroElectroMechanical Systems (MEMS) implied monolithic integration of these devices with the driving, controlling and signal processing electronics on the same CMOS substrate as this can improve performance, yield and reliability as well as lower the manufacturing, packaging and instrumentation costs. The post-processing route (fabricating MEMS on top of CMOS) is preferred as it avoids introducing any changes in standard foundry CMOS processes. Depending on the specific metallization type and the design requirements, post-processing limits the maximum fabrication temperature of MEMS to 450°C or 520°C [1], as this avoids introducing any damage or degradation to interconnects. This temperature constraint is quite strict for post processing surface micromachined MEMS, as it might affect relevant physical properties of the active element of MEMS such as crystallization, growth rate, mechanical properties, dopant activation, electrical resistivity, etc.. Polycrystalline silicon germanium (poly SiGe) is an attractive material for such applications due to its low amorphous to polycrystalline transition temperature, which can be as low as 400°C (with the appropriate germanium content). Furthermore, the mechanical properties of poly SiGe proved to be suitable for surface micromachining application [2]. In addition it is compatible with standard IC fabrication process, and hence it enables monolithic integration of MEMS with the driving electronics.
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Borenstein, Jeffrey T., Kevin R. King, Hidetomi Terai, and Joseph P. Vacanti. "Capillary Formation In Microfabricated Polymer Scaffolds." MRS Proceedings 711 (2001). http://dx.doi.org/10.1557/proc-711-gg1.3.1.
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ABSTRACTOne of the primary challenges for engineering thick, complex tissues such as vital organs is the requirement for a vascular supply for nutrient and metabolite transfer. Earlier work has shown that Solid Freeform Fabrication techniques such as Three-Dimensional Printing (3DP) are capable of producing biodegradable scaffolds for the subsequent formation of a wide range of tissues and organs. While this approach shows great promise as a method for constructing complex tissues and organs in vitro, the resolution of the process is currently limited to length scales larger than the narrowest capillaries in the microcirculation. In this work, microfabrication technology is demonstrated as an approach for organizing endothelial cells in vitro at the size scale of the microcirculation. Standard process techniques utilized to build MEMS (MicroElectroMechanical Systems) devices include photolithography, silicon and glass micromachining, and polymer replica molding. Photolithography is used to print a model network of blood vessels on silicon wafers; the network is designed to replicate the fluid dynamics of the vasculature of a particular tissue or organ. A reverse image of the channel network is formed either by Deep Reactive Ion Etching (DRIE) of silicon or through the use of a thick negative-polarity photoresist (SU-8). Polymeric scaffolds are formed by replica molding, using the silicon wafer as a master mold. Microfluidic chambers have been constructed from PDMS and other biocompatible polymers. Initial cell seeding experiments demonstrate that rat lung endothelial cells attach in a single layer to the walls of these structures without occluding them, providing early evidence that MEMS process technology can serve as a method for organizing capillary networks.
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Swarnalatha, V., S. Purohit, P. Pal, and R. K. Sharma. "Enhanced etching characteristics of Si{100} in NaOH-based two-component solution." Micro and Nano Systems Letters 10, no. 1 (August 1, 2022). http://dx.doi.org/10.1186/s40486-022-00152-9.
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AbstractSilicon wet bulk micromachining is the most widely used technique for the fabrication of diverse microstructures such as cantilevers, cavities, etc. in laboratory as well as in industry for micro-electromechanical system (MEMS) application. Although, increasing the throughput remains inevitable, and can be done by increasing the etching rate. Furthermore, freestanding structure release time can be reduced by the improved undercutting rate at convex corners. In this work, we have investigated the etching characteristics of a non-conventional etchant in the form of hydroxylamine (NH2OH) added sodium hydroxide (NaOH) solution. This research is focused on Si{100} wafer as this orientation is largely used in the fabrication of planer devices (e.g., complementary metal-oxide semiconductors) and microelectromechanical systems (e.g., inertial sensors). We have performed a systematic and parametric analysis without and with 12% NH2OH in 10 M NaOH for improved etching characteristics such as etch rate, undercutting at convex corners, and etched surface morphology. 3D scanning laser microscope is used to measure average surface roughness (Ra), etch depth (d), and undercutting length (l). Morphology of the etched Si{100} surface is examined using optical and scanning electron microscopes. The addition of NH2OH in NaOH solution remarkably exhibited a two-fold increment in the etching rate of a Si{100} surface. Furthermore, the addition of NH2OH significantly improves the etched surface morphology and undercutting at convex corners. Undercutting at convex corners is highly prudent for the quick release of microstructures from the substrate. In addition, we have studied the effect of etchant age on etching characteristics. Results presented in this article are of large significance for engineering applications in both academic and industrial laboratories.