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Fundamentals of MEMS Fabrication
Published in Sergey Edward Lyshevski, Mems and Nems, 2018
Surface micromachining has been widely used in commercial fabrication of MEMS and microdevices (microtransducers, actuators and sensors such as rotational/translational microservos, accelerometers, gyroscopes, etc.), and microstructures (gears, flip-chip electrostatic actuators, membranes, mirrors, etc.). As was emphasized, surface micromachining means the fabrication of micromechanical structures and devices by deposition and etching of structural and sacrificial layers (thin films). Simple microstructures (beams, gears, membranes, etc.) and complex microdevices (actuators, motors, and sensors) are fabricated on top of a silicon substrate. The most important attractive features of the surface micromachining technology are the small microstructure dimensions and the opportunity to integrate micromechanics, microelectronics (ICs), and optics on the same chip. Using the ICs compatible batch processing, affordable, low-cost, high-yield microstructure fabrication is achieved for high volume applications. For example, to fabricate microscale gears (microgear train), a sacrificial silicon dioxide is deposited on the wafer and patterned. Then, a structural layer of polysilicon is deposited and patterned. This polysilicon layer becomes the structural microgears element. Other layers are then deposited and patterned making the rest of the microstructure (microscale gears). Etching in the hydrofluoric or buffered hydrofluoric acids removes the sacrificial layers releasing the microgear [1].
MEMS Fabrication
Published in Mohamed Gad-el-Hak, MEMS, 2005
The most widely used structural material in surface micromachining is polysilicon (poly-Si, or simply poly). Polysilicon is deposited by low-pressure (25 to 150 Pa) chemical vapor deposition (LPCVD) in a furnace (a poly chamber) at about 600°C. The undoped material is usually deposited from pure silane, which thermally decomposes according to the reaction: () SiH4→Si+2H2
Fundamentals of Microfabrication and MEMS Fabrication Technologies
Published in Sergey Edward Lyshevski, Nano- and Micro-Electromechanical Systems, 2018
Surface micromachining has become the major fabrication technology in recent years because it allows one to fabricate complex three-dimensional microscale structures and devices. Surface micromachining with single-crystal silicon, polysilicon, silicon nitride, silicon oxide, and silicon dioxide (as structural and sacrificial materials that are deposited and etched), as well as metals and alloys, is widely used to fabricate thin micromechanical structures and devices on the surface of a silicon wafer.
A review of medical wearables: materials, power sources, sensors, and manufacturing aspects of human wearable technologies
Published in Journal of Medical Engineering & Technology, 2023
Mohammad Y. Al-Daraghmeh, Richard T. Stone
With the beginning of the twenty-one century, a significant amount of research has been conducted on wearable TEGs, both rigid TEGs and flexible TEGs, with more recent emphasis on flexible TEGs, which are more suited to generate power from body heat as they can adapt to the shape of the body. Regarding rigid substrate TEGs, BiTe3 alloy on an Aluminium type 6063-T4 surface plates was discussed for proposed self-powered TEG wearable applications [37]. In addition, polycrystalline silicon-germanium alloy on a Silicon substrate was investigated to develop a TEG by surface micromachining for human body applications [38]. Bi2Te3-based alloys were patterned using screen printing using the stencil method on Al2O3 rigid substrate [39]. TEG also has been hybridised with PV cells which have been fabricated on silicon substrate to improve an EEG system [40].
Studies on Gas Flow through Smooth Microchannel Surface – Fabrication, Characterization, Analysis, and Tangential Momentum Accommodation Coefficient Comparison
Published in Heat Transfer Engineering, 2020
Kandaswamy Srinivasan, Paruchuri M.V. Subbarao, Sunil R. Kale
The traditional methods for fabricating microchannels are silicon/bulk micromachining and photolithographic techniques. Microchannels were fabricated in a single crystal silicon wafer which was then covered with a thin silicon nitride membrane or bonded with a glass plate. Since the silicon nitride membrane thickness was only 1–2 μm and the experiments were conducted at high pressures (100–400 kPa), the channel walls were subjected to deformations which caused changes in the dimensions. A well-controlled surface structure is no longer attained due to the dissimilar materials in the lower and upper surfaces. The resulting channel has different surface roughness. In many microfluidic devices for electrical, mechanical, chemical, and biological applications, the fluid flows on the surface of silicon where the surface roughness varies between 0.1 and 1 nm. Hence it is important to study the gaseous flow characteristics in such range of channel surface roughness with similar top and bottom surfaces. However, most experimental studies have been performed on rough channel surfaces (roughness varied between 10 and 1,600 nm) and TMAC was calculated for different gases [9,10,19,27–29]. The experimental studies on smooth surfaces are rather few. Till to date, except Arkilic et al. [30], due to complexities in fabricating smooth microchannels most of the previous works were performed by etching the silicon surface and covering with a glass plate. The temperature, time and voltage at which the bonding between glass and silicon occur are well-defined, but parameters at which the contact between glass and any of the membrane materials or films used for surface micromachining are not well-developed and still under investigation.
Modeling analysis and fabrication of MEMS capacitive differential pressure sensor for altimeter application
Published in Journal of the Chinese Institute of Engineers, 2018
Eswaran Parthasarathy, S. Malarvizhi
The fabrication of a MEMS highly sensitive CDPS structure is based on bulk and surface micromachining techniques. In bulk micromachining, a portion of the substrate is removed using wet etchant, to create a cavity and via in the sensor structure. The material’s etch rates, and etching profiles are considered based on the literature (Kirt and Richard 1996). Surface micromachining methods are extensively adopted for the development of thin film structure on the silicon wafer.