giới thiệu về MEMS
(MicroElectroMechanical Systems) Tiny mechanical devices that are built onto semiconductor chips and are measured in micrometers. In the research labs since the 1980s, MEMS devices began to materialize as commercial products in the mid-1990s. They are used to make pressure, temperature, chemical and vibration sensors, light reflectors and switches as well as accelerometers for airbags, vehicle control, pacemakers and games. The technology is also used to make inkjet print heads, microactuators for read/write heads and all-optical switches that reflect light beams to the appropriate output port. See accelerometer. MEMS and MOEMS When optical components are included in a MEMS device, it is called a micro-opto- electromechanical system (MOEMS). For example, adding a photonic sensor to a silicon chip constitutes a MOEMS device. See micromachine, MEMS mirror,DLP and optical switch. MEMS Vs. Nanotechnology Sometimes MEMS and nanotechnology are terms that are used interchangeably, because they both deal with microminiaturized objects. However, they are vastly different. MEMS deals with creating devices that are measured in micrometers, whereas nantotechnology deals with manipulating atoms at the nanometer level. MEMS-based Optical Switch In an all-optical switch, MEMS mirrors reflect the input signal to an output port without regard to line speed or protocol. This technology is expected to be the dominant method for building photonic switches. Sample Micromachines Microfabrica's EFAB system was the first MEMS foundry process to accept CAD files as input, turning customer designs into micromachines much faster than traditional methods. EFAB builds the devices one metal layer at a time. In this image, the square at the top is a microfluidics device with internal passageways used for a "lab on a chip." The multi-arm device (center) is a fuel injection nozzle. Bottom left is an accelerometer, and bottom right is an inductor used in RF circuits. (Image courtesy of Microfabrica Inc., www.microfabrica.com) MEMS-Based Accelerometer MEMSIC's dual-axis thermal accelerator is a MEMS-based semiconductor device that works conceptually like the air bubble in a construction level. The square in the middle of the chip is a resistor that heats up a gas bubble. The next larger squares contain thermal couples that sense the location of the heated bubble as the device is tilted or accelerated. (Image courtesy of MEMSIC, Inc.) Download Computer Desktop Encyclopedia to your PC, iPhone or Android. • Unanswered Questions • New Answers • Q&A Categories • Coupons • Guides • Sign In • | • Sign Up • Home • Search • Settings • Top Contributors • Help Center Home Featured Videos: Top • o Play What Are Brain Orgasms and ASMR Whisperers? Play How Do the Engines Breathe In Diesel Submarines? Play Are Students Relying on Adderall Too Much? Ask us anything Play Optogenetics and Brain Function Enhancement • o • o • o • o View more Science videos Wikipedia on Answers.com: Microelectromechanical systems Top Home > Library > Miscellaneous > Wikipedia Microelectromechanical systems (MEMS) (also written as micro-electro- mechanical, MicroElectroMechanical ormicroelectronic and microelectromechanical systems) is the technology of very small devices; it merges at the nano-scale into nanoelectromechanical systems (NEMS) and nanotechnology. MEMS are also referred to as micromachines(in Japan), or micro systems technology – MST (in Europe). MEMS are separate and distinct from the hypothetical vision of molecular nanotechnology or molecular electronics. MEMS are made up of components between 1 to 100 micrometres in size (i.e. 0.001 to 0.1 mm), and MEMS devices generally range in size from 20 micrometres (20 millionths of a metre) to a millimetre (i.e. 0.02 to 1.0 mm). They usually consist of a central unit that processes data (the microprocessor) and several components that interact with the outside such as microsensors. [1] At these size scales, the standard constructs of classical physics are not always useful. Because of the large surface area to volume ratio of MEMS, surface effects such as electrostatics and wettingdominate over volume effects such as inertia or thermal mass. The potential of very small machines was appreciated before the technology existed that could make them—see, for example, Richard Feynman's famous 1959 lecture There's Plenty of Room at the Bottom. MEMS became practical once they could be fabricated using modified semiconductor device fabrication technologies, normally used to makeelectronics. These include molding and plating, wet etching (KOH, TMAH) and dry etching (RIE and DRIE), electro discharge machining (EDM), and other technologies capable of manufacturing small devices. An early example of a MEMS device is the resonistor – an electromechanical monolithic resonator. [2] [3] Contents 1 Materials for MEMS manufacturing o 1.1 Silicon o 1.2 Polymers o 1.3 Metals o 1.4 Ceramics 2 MEMS basic processes o 2.1 Deposition processes 2.1.1 Physical deposition 2.1.1.1 Physical vapor deposition (PVD) 2.1.2 Chemical deposition o 2.2 Patterning 2.2.1 Lithography 2.2.1.1 Photolithography 2.2.1.2 Electron beam lithography 2.2.1.3 Ion beam lithography 2.2.1.4 Ion track technology 2.2.1.5 X-ray lithography 2.2.2 Diamond patterning o 2.3 Etching processes 2.3.1 Wet etching 2.3.1.1 Isotropic etching 2.3.1.2 Anisotropic etching 2.3.1.3 HF etching 2.3.1.4 Electrochemical etching 2.3.2 Dry etching 2.3.2.1 Vapor etching 2.3.2.1.1 Xenon difluoride etching 2.3.2.2 Plasma etching 2.3.2.2.1 Sputtering 2.3.2.2.2 Reactive ion etching (RIE) o 2.4 Die preparation 3 MEMS manufacturing technologies o 3.1 Bulk micromachining o 3.2 Surface micromachining o 3.3 High aspect ratio (HAR) silicon micromachining 4 Applications 5 Industry structure 6 See also 7 References 8 External links Materials for MEMS manufacturing The fabrication of MEMS evolved from the process technology in semiconductor device fabrication, i.e. the basic techniques are deposition of material layers, patterning by photolithography and etching to produce the required shapes. [4] Silicon Silicon is the material used to create most integrated circuits used in consumer electronics in the modern industry. The economies of scale, ready availability of cheap high-quality materials and ability to incorporate electronic functionality make silicon attractive for a wide variety of MEMS applications. Silicon also has significant advantages engendered through its material properties. In single crystal form, silicon is an almost perfect Hookean material, meaning that when it is flexed there is virtually no hysteresis and hence almost no energy dissipation. As well as making for highly repeatable motion, this also makes silicon very reliable as it suffers very little fatigue and can have service lifetimes in the range of billions to trillions of cycles without breaking. Polymers Even though the electronics industry provides an economy of scale for the silicon industry, crystalline silicon is still a complex and relatively expensive material to be produced. Polymers on the other hand can be produced in huge volumes, with a great variety of material characteristics. MEMS devices can be made from polymers by processes such as injection molding, embossing or stereolithography and are especially well suited to microfluidic applications such as disposable blood testing cartridges. Metals Metals can also be used to create MEMS elements. While metals do not have some of the advantages displayed by silicon in terms of mechanical properties, when used within their limitations, metals can exhibit very high degrees of reliability. Metals can be deposited by electroplating, evaporation, and sputtering processes. Commonly used metals include gold, nickel, aluminium, copper, chromium, titanium, tungsten, platinum, and silver. Ceramics The nitrides of silicon, aluminium and titanium as well as silicon carbide and other ceramics are increasingly applied in MEMS fabrication due to advantageous combinations of material properties. AlN crystallizes in the wurtzite structureand thus shows pyroelectric and piezoelectric properties enabling sensors, for instance, with sensitivity to normal and shear forces. [5] TiN , on the other hand, exhibits a high electrical conductivity and large elastic modulus allowing to realize electrostatic MEMS actuation schemes with ultrathin membranes. [6] Moreover, the high resistance of TiN against biocorrosion qualifies the material for applications in biogenic environments and in biosensors. MEMS basic processes This chart is not complete: B as ic P ro c es s D e p o si ti o n P at te rn in g Etching Deposition processes One of the basic building blocks in MEMS processing is the ability to deposit thin films of material with a thickness anywhere between a few nanometres to about 100 micrometres. Physical deposition There are two types of deposition processes. They are as follows. Physical vapor deposition (PVD) Physical vapor deposition consists of a process in which a material is removed from a target, and deposited on a surface. Techniques to do this include the process of sputtering, in which an ion beam liberates atoms from a target, allowing them to move through the intervening space and deposit on the desired substrate, and Evaporation (deposition), in which a material is evaporated from a target using either heat (thermal evaporation) or an electron beam (e-beam evaporation) in a vacuum system. Chemical deposition Chemical deposition techniques include chemical vapor deposition ("CVD"), in which a stream of source gas reacts on the substrate to grow the material desired. This can be further divided into categories depending on the details of the technique, for example, LPCVD (Low Pressure chemical vapor deposition) and PECVD (Plasma Enhanced chemical vapor deposition). Oxide films can also be grown by the technique of thermal oxidation, in which the (typically silicon) wafer is exposed to oxygen and/or steam, to grow a thin surface layer of silicon dioxide. Patterning Patterning in MEMS is the transfer of a pattern into a material. Lithography Lithography in MEMS context is typically the transfer of a pattern into a photosensitive material by selective exposure to a radiation source such as light. A photosensitive material is a material that experiences a change in its physical properties when exposed to a radiation source. If a photosensitive material is selectively exposed to radiation (e.g. by masking some of the radiation) the pattern of the radiation on the material is transferred to the material exposed, as the properties of the exposed and unexposed regions differs. This exposed region can then be removed or treated providing a mask for the underlying substrate.Photolithography is typically used with metal or other thin film deposition, wet and dry etching. Photolithography [...]... systems are similar to MEMS but smaller Micro-opto-electromechanical systems, MEMS including optical elements Micropower Hydrogen generators, gas turbines, and electrical generators made of etched silicon Millipede memory, a MEMS technology for non-volatile data storage of more than a terabit per square inch Cantilever one of the most common forms of MEMS MEMS thermal actuator MEMS actuation created... manufacture MEMS devices topped $1 billion worldwide in 2006 Materials demand is driven by substrates, making up over 70 percent of the market, packaging coatings and increasing use of chemical mechanical planarization (CMP) While MEMS manufacturing continues to be dominated by used semiconductor equipment, there is a migration to 200 mm lines and select new tools, including etch and bonding for certain MEMS. .. controlled polysilicon was advocated by the UC Berkeley group Applications microelectromechanical systems chip, sometimes called "lab on a chip" In one viewpoint MEMS application is categorized by type of use Sensor Actuator Structure In another view point MEMS applications are categorized by the field of application (commercial applications include): Inkjet printers, which use piezoelectrics or thermal... to explore MEMS technology Industry structure The global market for micro-electromechanical systems, which includes products such as automobile airbag systems, display systems and inkjet cartridges totaled $40 billion in 2006 according to Global MEMS/ Microsystems Markets and Opportunities, a research report from SEMI and Yole Developpement and is forecasted to reach $72 billion by 2011 [18] MEMS devices... former, the material is dissolved when immersed in a chemical solution In the latter, the material is sputtered or dissolved using reactive ions or a vapor phase etchant [8][9] for a somewhat dated overview of MEMS etching technologies Wet etching Main article: Wet etching Wet chemical etching consists in selective removal of material by dipping a substrate into a solution that dissolves it The chemical... Digital IXUS models) Also used in PCs to park the hard disk head when free-fall is detected, to prevent damage and data loss MEMS gyroscopes used in modern cars and other applications to detect yaw; e.g., to deploy a roll over bar or trigger dynamic stability control[16] MEMS microphones in portable devices, e.g., mobile phones, head sets and laptops Silicon pressure sensors e.g., car tire pressure... of combining MEMS and integrated circuits on the same silicon wafer The original surface micromachining concept was based on thin polycrystalline silicon layers patterned as movable mechanical structures and released by sacrificial etching of the underlying oxide layer Interdigital comb electrodes were used to produce in-plane forces and to detect in-plane movement capacitively This MEMS paradigm... preparing a large number of MEMS devices on a silicon wafer, individual dies have to be separated, which is called die preparation in semiconductor technology For some applications, the separation is preceded by wafer backgrinding in order to reduce the wafer thickness Wafer dicing may then be performed either by sawing using a cooling liquid or a dry laser process called stealth dicing MEMS manufacturing technologies... the most common forms of MEMS MEMS thermal actuator MEMS actuation created by thermal expansion Scratch Drive Actuator MEMS actuation using repeatedly applied voltage differences Electrostatic motors used where coils are difficult to fabricate Brain–computer interface MEMS sensor generations Kelvin probe force microscope References 1 ^ Waldner, Jean-Baptiste (2008) Nanocomputers and Swarm... 144–147.doi:10.1016/j.proche.2009.07.036 6 ^ M Birkholz, K.-E Ehwald, P Kulse, J Drews, M Fröhlich, U Haak, M Kaynak, E Matthus, K Schulz, D Wolansky (2011) "Ultrathin TiN Membranes as a Technology Platform for CMOS-Integrated MEMS and BioMEMS Devices" Adv Func Mat 21: 1652– 1656 doi:10.1002/adfm.201002062 7 ^ McCord, M A.; M J Rooks (2000) "2" SPIE Handbook of Microlithography, Micromachining and Microfabrication 8 ^ Williams, K.R.; . called "lab on a chip" In one viewpoint MEMS application is categorized by type of use. Sensor Actuator Structure In another view point MEMS applications are categorized by the. Millipede memory , a MEMS technology for non-volatile data storage of more than a terabit per square inch Cantilever one of the most common forms of MEMS. MEMS thermal actuator MEMS actuation. dissolved using reactive ions or a vapor phase etchant. [8] [9] for a somewhat dated overview of MEMS etching technologies. Wet etching Main article: Wet etching Wet chemical etching consists