What is MEMS Technology?Micro-Electro-Mechanical Systems, or MEMS, is a technology that in its most general form can be defined as miniaturized mechanical and electro-mechanical elements (i.e., devices and structures) that are made using the techniques of microfabrication. The critical physical dimensions of MEMS devices can vary from well below one micron on the lower end of the dimensional spectrum, all the way to several millimeters. Likewise, the types of MEMS devices can vary from relatively simple structures having no moving elements, to extremely complex electromechanical systems with multiple moving elements under the control of integrated microelectronics. The one main criterion of MEMS is that there are at least some elements having some sort of mechanical functionality whether or not these elements can move. The term used to define MEMS varies in different parts of the world. In the United States they are predominantly called MEMS, while in some other parts of the world they are called Microsystems Technology or micromachined devices. While the functional elements of MEMS are miniaturized structures, sensors, actuators, and microelectronics, the most notable (and perhaps most interesting) elements are the microsensors and microactuators. Microsensors and microactuators are appropriately categorized as transducers, which are defined as devices that convert energy from one form to another. In the case of microsensors, the device typically converts a measured mechanical signal into an electrical signal.

Over the past several decades MEMS researchers and developers have demonstrated an extremely large number of microsensors for almost every possible sensing modality including temperature, pressure, inertial forces, chemical species, magnetic fields, radiation, etc. Remarkably, many of these micromachined sensors have demonstrated performances exceeding those of their macroscale counterparts. That is, the micromachined version of, for example, a pressure transducer, usually outperforms a pressure sensor made using the most precise macroscale level machining techniques. Not only is the performance of MEMS devices

exceptional, but their method of production leverages the same batch fabrication techniques used in the integrated circuit industry which can translate into low per-device production costs, as well as many other benefits. Consequently, it is possible to not only achieve stellar device performance, but to do so at a relatively low cost level. Not surprisingly, silicon based discrete microsensors were quickly commercially exploited and the markets for these devices continue to grow at a rapid rate. More recently, the MEMS research and development community has demonstrated a number of microactuators including: microvalves for control of gas and liquid flows; optical switches and mirrors to redirect or modulate light beams; independently controlled micromirror arrays for displays, microresonators for a number of different applications, micropumps to develop positive fluid pressures, microflaps to modulate airstreams on airfoils, as well as many others. Surprisingly, even though these microactuators are extremely small, they frequently can cause effects at the macroscale level; that is, these tiny actuators can perform mechanical feats far larger than their size would imply. For example, researchers have placed small microactuators on the leading edge of airfoils of an aircraft and have been able to steer the aircraft using only these microminiaturized devices.

A surface micromachined electro-statically-actuated micromotor fabricated by the MNX. This device is an example of a MEMS-based microactuator.

The real potential of MEMS starts to become fulfilled when these miniaturized sensors, actuators, and structures can all be merged onto a common silicon substrate along with integrated circuits (i.e., microelectronics). While the electronics are fabricated using integrated circuit (IC) process sequences (e.g., CMOS, Bipolar, or BICMOS processes), the micromechanical components are fabricated using compatible "micromachining" processes that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices. It is even more interesting if MEMS can be merged not only with microelectronics, but with other technologies such as photonics, nanotechnology, etc. This is sometimes called heterogeneous integration. Clearly, these technologies are filled with numerous commercial market opportunities.

While more complex levels of integration are the future trend of MEMS technology, the present state-of-the-art is more modest and usually involves a single discrete microsensor, a single discrete microactuator, a single microsensor integrated with electronics, a multiplicity of essentially identical microsensors integrated with electronics, a single microactuator integrated with electronics, or a multiplicity of essentially identical microactuators integrated with electronics. Nevertheless, as MEMS fabrication methods advance, the promise is an enormous design freedom wherein any type of microsensor and any type of microactuator can be merged with microelectronics as well as photonics, nanotechnology, etc., onto a single substrate.

A surface micromachined resonator fabricated by the MNX. This device can be used as both a microsensor as well as a microactuator.

This vision of MEMS whereby microsensors, microactuators and microelectronics and other technologies, can be integrated onto a single microchip is expected to be one of the most important technological breakthroughs of the future. This will enable the development of smart products by augmenting the computational ability of microelectronics with the perception and control capabilities of microsensors and microactuators. Microelectronic integrated circuits can be thought of as the "brains" of a system and MEMS augments this decision-making capability with "eyes" and "arms", to allow microsystems to sense and control the environment. Sensors gather information from the environment through measuring mechanical, thermal, biological, chemical, optical, and magnetic phenomena. The electronics then process the information derived from the sensors and through some decision making capability direct the actuators to respond by moving, positioning, regulating, pumping, and filtering, thereby controlling the environment for some desired outcome or purpose. Furthermore, because MEMS devices are manufactured using batch fabrication techniques, similar to ICs, unprecedented levels of functionality, reliability, and sophistication can be placed on a small silicon chip at a relatively low cost. MEMS technology is extremely diverse and fertile, both in its expected application areas, as well as in how the devices are designed and manufactured. Already, MEMS is revolutionizing many product categories by enabling complete systems-on-a-chip to be realized.

Nanotechnology is the ability to manipulate matter at the atomic or molecular level to make something useful at the nano-dimensional scale. Basically, there are two approaches in implementation: the top-down and the bottom-up. In the top-down approach, devices and structures are made using many of the same techniques as used in MEMS except they are made smaller in size, usually by employing more advanced photolithography and etching methods. The bottom-up approach typically involves deposition, growing, or self-assembly technologies. The advantages of nano-dimensional devices over MEMS involve benefits mostly derived from the scaling laws, which can also present some challenges as well.

An array of sub-micron posts made using top-down nanotechnology fabrication methods.

Some experts believe that nanotechnology promises to: a). allow us to put essentially every atom or molecule in the place and position desired that is, exact positional control for assembly, b). allow us to make almost any structure or material consistent with the laws of physics that can be specified at the atomic or molecular level; and c). allow us to have manufacturing costs not greatly exceeding the cost of the required raw materials and energy used in fabrication (i.e., massive parallelism).

A colorized image of a scanning-tunneling microscope image of a surface, which is a common imaging technique used in nanotechnology.

Although MEMS and Nanotechnology are sometimes cited as separate and distinct technologies, in reality the distinction between the two is not so clear-cut. In fact, these two technologies are highly dependent on one another. The well-known scanning tunneling-tip microscope (STM) which is used to detect individual atoms and molecules on the nanometer scale is a MEMS device. Similarly the atomic force microscope (AFM) which is used to manipulate the placement and position of individual atoms and molecules on the surface of a substrate is a MEMS device as well. In fact, a variety of MEMS technologies are required in order to interface with the nanoscale domain.

Likewise, many MEMS technologies are becoming dependent on nanotechnologies for successful new products. For example, the crash airbag accelerometers that are manufactured using MEMS technology can have their long-term reliability degraded due to dynamic in-use stiction effects between the proof mass and the substrate. A nanotechnology called SelfAssembled Monolayers (SAM) coatings are now routinely used to treat the surfaces of the moving MEMS elements so as to prevent stiction effects from occurring over the products life. Many experts have concluded that MEMS and nanotechnology are two different labels for what is essentially a technology encompassing highly miniaturized things that cannot be seen with the human eye. Note that a similar broad definition exists in the integrated circuits domain which is frequently referred to as microelectronics technology even though state-of-the-art IC technologies typically have devices with dimensions of tens of nanometers. Whether or not MEMS and nanotechnology are one in the same, it is unquestioned that there are overwhelming mutual dependencies between these two technologies that will only increase in time. Perhaps what is most important are the common benefits afforded by these technologies, including: increased information capabilities; miniaturization of systems; new materials resulting from new science at miniature dimensional scales; and increased functionality and autonomy for systems. Whether you are interested in developing MEMS or nano-devices, the MNX is the worlds leading fabricator for these technologies and can help you with your development or research project.Cu trc c bn ca mt thit b MEMS gm : b phn vi cm bin ( sensor), b vi chp hnh ( actuator), mch vi in t v cu trc vi c.

Trong b phn cm bin c ch to bng cng ngh vi c ( micromachining) cn phn in t c lm bng cng ngh vi in t. V tt c c tch hp trn cng mt chip c kch thc nh gn :

Cc cu trc vi c tht mong manh nhng tht p ! Di y l mt s cu trc vi c sc nt ch to bng cng ngh n mn kh ( dng chm ion ...)

Cc cm bin, b phn quan trng nht trong thit b MEMS, c ch to rt a dng v chng loi v hnh thi . Di y l mt s cu trc i din :

1. MEMS - Tch hp tinh vi in v c Ta thng nghe ni n cng ngh vi in t ch to ra vi mch hay mch tch hp. Trn mt phin bn dn, thng l silic ngi ta c th to ra lp mng oxyt silic cch in, bo v, lp silic pha tp loi p, loi n lm ra tranzito, lp kim loi lm in cc, dn in v.v... Cng ngh vi in t t c nh cao, trn mt mnh silic din tch c vi centimet vung c th lm n t vi trm triu n mt t linh kin, to thnh mt mch chc nng nh rt nhiu, x l cc nhanh, l tri tim ca my tnh. Tuy nhin cng ngh vi in t ch lm c nhng linh kin in, nm trn mt phng gn cht vi silic. Mch tch hp cc k phc tp, c rt nhiu in cc vo v ra, thc hin nhiu chc nng nhng ch l cc chc nng v in. Mch tch hp khng th lm cc chc nng th d v c nh quay, dch chuyn, dao ng, bm v.v... Nu cn c cc b phn thc hin nhng

chc nng v c th cc b phn ny c ch to theo kiu c in, phi ghp ni th cng vi mch tch hp, tt nhin l rt cng knh. Gn y cng ngh ch to tch hp linh kin c v linh kin in t c pht trin mnh, thng c gi l cng ngh ch to cc h vi c in - MEMS (Micro Electro Mechanical Systems). V mt chuyn mn, cng ngh MEMS gii quyt c nhiu yu cu k thut theo cch hon ton mi. Th d xe t, trc ch ngi ca hnh khch m bo an ton ngi ta t nhng ti rng ng kh nhng xp nh, du kn khng trng thy. Trng hp xe b va chm tc l lc c gia tc t ngt (gia tc m), b phn t ng s iu khin cc nhanh cho kh x ra, cng phng ti kh, ngi chm ln ch va vo ti kh. Trc y b cm bin gia tc iu khin t ng to bng lon nc gii kht gi hn 15 la, nay lm bng cng ngh MEMS nhy hn, nh hn t ngn tay gi ch vi la. Tnh ra trong mt chic xe t hin i c n 80 b cm bin lm theo cng ngh MEMS nh vy (iu khin ti kh, theo di p sut v nhit bnh xe, iu khin bm khi lp non hi, theo di du m bi trn, nc lm ngui v.v...). Nhiu loi t ng cng knh trc y, nay c thay th bng cc linh kin vi c in th tch khng ng k, cht lng hn hn. Tnh ra mi nm dng ring cho xe t ngi ta sn xut 100 triu linh kin MEMS. Mt th d na l linh kin DMD (Digital Micromirror Device - linh kin gng vi m k thut s). l mt h gm c mt triu gng , mi gng kch thc 16x16 micromet vung, c th quay trong phm vi ? 10o iu khin bng mch vi in t, tt c u c ch to trn mt phin silic. Cc gng kht nhau c xp thnh hng, thnh dy trt t v mi gng c mt tia sng (laze mu) chiu vo. Chng trnh ci t my vi tnh iu khin cc gng quay sao cho cc tia phn x hoc khng phn x, chiu ln mn nh (tm vi, bc tng) to ra hnh nh. Linh kin nh gn, c ng kn, khng b hi nc v bi nh hng, c s dng ph bin cc my chiu phim k thut s, my chiu hnh iu khin bng vi tnh thuyt trnh cc cuc hi tho v.v... Ra i cha c bao lu nhng n nay c mt triu linh kin DMD c a ra s dng, nng cao hn k thut nghe nhn. Trc khi xt c th hn mt s linh kin MEMS ang c nhng ng gp ln cho cng ngh thng tin, ta tm hiu vic ch to MEMS nh th no. 2. Ch to MEMS nh th no ? Cng ngh ch to MEMS k tha cng ngh vi in t nhng pht trin mi nhiu k thut m cng ngh vi in t khng c, khng lm c. Trc ht cng ngh MEMS s dng rt nhiu k thut x l gia cng trn b mt nh cng ngh vi in t v cng s dng vt liu chnh l silic.

Trn phin silic, theo thit k, ngi ta to ra cc lp oxyt silic cch in, pha tp c bn dn loi n, loi p, to ra cc lp silic a tinh th dn in, to ra cc lp nitrit silic rt CNG, N HI V.V... P DNG CC K thut khc hnh ca cng ngh vi in t, cc k thut to cc ng dn in rt tinh vi, c th lm ra c mt mch in thc hin mt chc nng no . Tuy nhin ch to MEMS bn cnh vic lm cc mch in phi lm c ngay trn phin silic cc chi tit thc hin cc chc nng v c. Chng phi linh ng, khng nm trn cng mt mt phng, khng gn cht vi phin silic. V vy bn cnh cc k thut ca cng ngh vi in t lm cc linh kin, cc chi tit gn cht vi phin silic cn c cc k thut c trng ca cng ngh MEMS l k thut lm tch ri. l cc k thut n mn chn lc, ha tan ht mt phn no ca ch li nhng chi tit mng gn nh t do, k thut LIGA dng cht cm kt hp vi nhiu cch khc to cc chi tit vung gc vi b mt silic, cc th thut dng ng (pop up)... Ta c th hnh dung kt qu ca cc qu trnh nh v trang ba 1: ban u dng cc k thut ca cng ngh vi in t to ra nhiu chi tit gn cht vi silic sau y dng cc k thut c th ca MEMS tch ri mt s chi tit . Hin nay mt nh my lm mch tch hp c gi thnh c 1 t la, lm vic trong 5 nm th xem nh sn phm mch tch hp b lc hu, phi thay th bng nh my khc cng ngh cao hn, hin i hn. Nhng nh my lm mch tch hp c li thi, li c th s dng tt lm cc h MEMS bng cch b sung nhng phng tin my mc thc hin k thut nh "tch ri", "gn kt"... Cc sn phm ca cng ngh MEMS chim th phn c hng chc t la mi nm. Sau y l hai th d v ng dng mi nht ca MEMS. 3. B nh tuyn quang hc Ta bit rng thng tin hin i s dng cp quang truyn tn hiu i xa, nhanh an ton. Nhng lu lng hng ngn t bit thng tin trong mt giy khng phi lun lun c truyn thng t u ny sang u kia ca mt si cp quang. C c mt mng li cc si cp quang ni vi nhau, thng tin c truyn i, lc r sang si ny, lc r sang SI KIA N A CH CN CHUYN TI. ni r, rt thng gp hin tng "tht c chai" nghn ng truyn tng t nh hin tng kt xe nt giao thng. l v phn t mang thng tin truyn theo cp quang l photon, trong cp quang, photon chuyn ng cc nhanh vi tc nh sng. Nhng photon ang i theo ng cp quang ny mun iu khin r sang ng kia (i tuyn) phi nh vo b nh tuyn (router). Lu nay b nh tuyn u lm vic theo nguyn tc bin photon n b nh tuyn thnh in t, dng mch in t iu khin cho in t r nhnh, sau khi in t r nhnh, li bin in t thnh photon truyn vo ng cp quang r. Vic bin i quang thnh in ri in thnh quang b nh tuyn nh vy lm hn ch tc truyn thng tin. Thc t thi gian bin i cho mi bit thng tin theo kiu ni trn l vi nano giy (1 nano giy = 10-9 giy). V vy khi lu lng thng tin ln hn gigabit/giy (1 gigabit = 109 bit) th bt u b chm, bt u th hin hin tng tht c chai (bottleness) khi i qua b

nh tuyn. Ngi ta ang tin n lu lng thng tin c terabit/giy, c th nhiu vn thng tin, trao i mi thc thi c. Do phi tm cch lm cc b nh tuyn hot ng theo nguyn l khc. Cng ngh MEMS cho php lm cc b nh tuyn hon ton khng c vn chuyn quang sang in ri in sang quang. Nguyn l rt n gin. Ngi ta t cc gng con u mt cc si cp quang ch cn r nhnh. Cc photon mang thng tin c truyn theo si quang khi n gng con s b phn x. Ty theo gc quay ca gng, tia phn x s chiu vo u si quang ny hay u si quang kia tc l photon r ng i theo cch phn x. Thc t thng tin ang truyn theo tuyn ny mun chuyn sang tuyn kia th ch cn mt thi gian1/5000 giy quay gng. Sau khi gng quay, cc photon c phn x r sang nhnh mong mun, hon ton khng mt thi gian chuyn i g na. Nguyn l th n gin nhng cng ngh ch to rt kh. Phi lm nhng gng phn x cc nh, b tr gn nhau v phi iu khin bng in cc gng ny quay nhanh chng (1/5000 giy) theo nhng gc nht nh. Vic ch to c mt h rt nh kt hp in v c ny chnh l thnh tu ca cng ngh MEMS. Thc t Lucent Technologies, mt n v ch lc ca Bell Labs ch to c b nh tuyn kiu ny, c tn l b nh tuyn Lamda. C th nh sau: nh tuyn dng cho cp quang, l mt b gm 256 si quang. B nh tuyn c u vo di dng ni vi cc u mt ca 256 si quang xp thnh hnh vung, mi hng c 16 ch "ni" vi cc u mt ca 16 si, c tt c 16 hng nh vy (16 x 16 = 256). C 256 gng phn x, mi gng c vi ng c iu khin cho gng quay. Vi ng c c dng hai l mng hnh ch S dn in. Khi c dng in chy qua, t trng dng in lm cho ch S b xon. Gng con gn cht vi ch S nn b xon theo, tc l quay. Ty theo dng in tc dng, vi ng c quay gng mt gc nht nh v thi gian thc hin thao tc ny c 1/5000 giy nh ni trn. Cc tia phn x t 256 gng con ny s n cc mt ca cc u si quang i ra, chng cng nm trn hnh vung 16x16 = 256 u mt. Tt c b nh tuyn ny u c lm trn mt mnh silic, ngoi cc qu trnh khc hnh lm ra mch vi in t iu khin cn c qu trnh lm gng, lm vi ng c, ban u trong mt phng sau y dng ln trong khng gian. 4. H vi in c iu nhit cho b vi x l Cc b vi x l hin nay lm theo cng ngh vi in t, trnh vi x l cng cao th cng tch hp nhiu linh kin in t. Th d b vi x l Pentium 4 hin nay cha n hn 40 triu tranzito trn mt din tch vi centimet vung. Tuy mi linh kin tiu th khng bao nhiu in nng nhng hng chc triu linh kin tp trung trn mt din tch NH NH VY TA RA MT NHIT LNG KH LN. Pentium 4 nhit n trn 80oC. lm cc b vi x l mnh hn na, vn thu nh kch thc tranzito, vn lm cho tranzito lm vic vi tc cao hn tiu th t nng lng hn l rt kh nhng vn gi cho nhit b vi x l khng tng ln cao qu l vn cn kh hn. Hin nay hng Intel sng to ra gii php dng h vi in c MEMS ta nhit.

Ta bit rng cc b vi x l hin nay vic ta nhit c gii quyt bng cch dng qut thi khng kh lm mt. B VI X L C N HNG T tranzito khng lu na c a vo s dng hng Intel thit k ch to b lm mt ti nhit ra ngoi bng cch bm cht lng nh sau: Pha di silic ca b vi x l ngi ta khc nhng ng ng kht nhau vng vo kiu rut g, ng knh ng l 280 nanomet ri y trong ng cht lng lm lnh. Mt my bm cng ch to theo cng ngh vi c in trn silic bm cho cht lng lu thng ti nhit t b vi x l n cc tm nhom ta nhit bn ngoi. Cng ngh MEMS rt quan trng ch b tr c cc nh gn, a cht lng lm lnh trc tip n di chn ca hng t tranzito, ti c nhit tp trung mt din tch rt nh nhanh chng cho ta ra ngoi. Trc y nhng nh cng ngh vi in t thng lo lng rng thit k nhng mch tch hp mt cc cao c vn nan gii l nhit ta ra ca hng t tranzito trn vi centimet vung, c th cao nh din tch ca mt tri. Phi chng cng ngh MEMS to ra gii php vt kh khn . 5. Bi hc t chic i bn dn c ? Nhiu ngi nh li khong 50 nm trc y, khi tranzito ra i thay th cho n in t chn khng, th mt chic i bn dn c 6 tranzito l nim kiu hnh v ci mi, ci hin i. T AI C TH HNH DUNG KHNG LU sau, i bn dn 6 tranzito l qu n gin, th s. C th khng lu na khi nhn mt thit b c gn vi b MEMS ta cng c cm tng nh khi nhn vo chic i bn dn c k. __________________