Current and Future Trends in Micro Electro Mechanical Systems - Case Study Example

CURRENT AND FUTURE TRENDS IN MICRO ELECTRO-MECHANICAL SYSTEMS MEMS or Micro Electro-Mechanical Systems, also referred to as micro-machinesis an emerging technology, which has had a phenomenal growth in the past decade. This technology is well suited to producing a class of micro-machined sensors and actuators that combines signal processing and communications on a single silicon chip or contained within the same package. This report consists of a review of the current trends in MEMS technology and an outline about the MEMS devices. Market analysis of MEMS applications and its future trends are also discussed. INTRODUCTION "The MEMS is the batch-fabricated integrated micro-scale system (motion, electromagnetic, radiating energy and optical micro-devices/microstructures - driving/sensing circuitry -controlling/processing ICs) that: converts physical stimuli, events, and parameters to electrical, mechanical, and optical signals and vice versa; performs actuation, sensing and other functions; comprise control (intelligence, decision-making, evolutionary learning, adaptation, self-organization, etc.), diagnostics, signal processing, and data acquisition features."[2] The term MEMS refer to the devices that are on a millimetre scale with micro-resolution. It is the integration of mechanical elements, sensors, actuators and electronics on common silicon substrate through the utilization of microfabrication technology [8]. This report discusses the various MEMS technologies, devices and their applications and also the market value for various MEMS products. MEMS TECHNOLOGIES There are several broad categories of MEMS fabrication technologies. They are Bulk micromachining, Surface micromachining, LIGA, Deep reactive ion etching and the integrated MEMS technologies. The brief [9] of each of the technologies is given below Bulk micromachining is a fabrication technique which builds mechanical elements by starting with a silicon wafer, and then etching away unwanted parts, and being left with useful mechanical devices [9].'The advantages are less cost high reliability, manufacturability, and good repeatability [9]. Surface Micromachining builds devices up from the wafer layer-by-layer [9]. Surface Micromachining requires more fabrication steps than Bulk Micromachining, and hence is more expensive.' It is able to create much more complicated devices, capable of sophisticated functionality. LIGA is a technology which creates small, but relatively high aspect ratio devices using x-ray lithography [9]. Unlike traditional Bulk Micromachining, which uses a wet chemical etch, Deep Reactive Ion Etching micromachining uses'a plasma etch to create features allowing greater flexibility in the etch profiles, enabling a wider array of mechanical elements [9]. Since MEMS devices are created with the same tools used to create integrated circuits, in some cases it is also possible to fabricate Micro-machines and Microelectronics on the same piece of silicon [9].' LITERATURE REVIEW MEMS has a very wide range of applications, particularly of its sensors which are used many of the automotive, medical and other consumer products. The technology development is immense and there are several in the literature to quote from in evidence of this fact. The MEMS related technology and literature work is very huge and hence effort has been made only to cover the key developments from random authors. One technique developed in the United States at the University of Wisconsin uses thin film polysilicon for the sensor diaphragm [3]. The polysilicon devices are correspondingly smaller and hence they cost less. Another technique, result in much smaller sensor dies than standard bulk micromachining techniques NovaSensor in the United States, employs high temperature fusion bonding of silicon wafers to form inward tapering cavities under single crystal silicon diaphragms [4]. These devices are used in medical catheters. An improvement in low pressure measurement has also been suggested as by using advanced MEMS micromachining technology to add corrugations or bosses to the diaphragm. Areas of stress concentration can be formed that facilitate these low pressure measurements [5]. Miniature silicon accelerometers are developed due to the large potential markets in automotive applications for sensors for air bag deployment and active suspensions. Several accelerometers using bulk silicon micromachining to form single crystal silicon proof mass and supporting flexures have been developed in the United States [6], and some are commercially available. Vibratory silicon gyroscopes have been demonstrated by Draper Lab and by Sundstrand [7]. MEMS technology is also being advantageously combined with optics for sensing example is the use of light beams to excite a microminiature resonant beam strain sensor and sense the beam's vibrational motion [1]. MEMS DEVICES MEMS devices can be broadly classified into sensors and actuators MEMS SENSORS Sensors may be classified according to the type of property they can measure. Some of the types of sensors in use are mechanical, thermal, radiation, magnetic, electrical, chemical and biological. Applications of pressure sensors include condition monitoring of refrigerators, automotive applications like Remote Tire Pressure Monitoring, Engine control (Manifold absolute pressure, MAP), Fuel tank and Exhaust gas pressure monitoring and medical applications like Respirators, ventilators, oxygen concentrators, Airflow application and to monitor Blood and fluid pressure [10]. MEMS motion sensors or the accelerometers are widely used for vibration detection in industries and side air bag crash detection in automobiles [10]. Two MEMS sensors have been described here. IMPEDIMETRIC BIO-SENSORS (IMEC) [10] Impedimetric biosensors allow for the detection of affinity binding of bio-molecular structures (e.g., antigens, DNA) by impedimetric measurements. Figure 1 Nanoscaled interdigitated electrode arrays are made with deep U.V. lithography. Electrode widths and spacings from 500 nm down to 250 nm are produced on large active areas (0.5 mm x 1 mm). This sensor measures the binding of a target molecule to selective probes by measuring changes in the electric properties in the vicinity of an electrode. The direct electrical read-out eliminates the need for optical components CONTACTLESS ANGULAR POSITION SENSOR [10] Figure 2 A small magnet rotating above a multidimensional Hall sensor is used to indicate the angular position of an axis. This sensor microsystem is produced in standard CMOS technology, in order to enable the integration of the first amplification levels. MEMS ACTUATORS By definition, MEMS actuators perform some action. Solid objects can be moved in a number of ways such as translation (example, pistons, comb drive, barrier insertion for optical switches), rotation (example, cogs, gears, micromotors) and tilting (example, mirrors). Actuators may be classified by their method of actuation [11]: Electrostatic, Magnetic, Piezoelectric, Thermal, Shape-memory alloys, Polyimide joint technology are some of the MEMS actuators in use. COMB DRIVE ELECTROSTATIC ACTUATOR [11] Figure 3 Lateral translation of the mobile parts for electrostatic actuation is mostly achieved with comb-drive actuators. The left side part is fixed and anchored to the substrate. The right part is free to move, except at the end where it is anchored to the substrate, so that the actuator can come back to its initial position due to the spring force. This allows the mobile part to move along the beam direction. MARKET ASSESSMENT The Nexus market analysis by application field of MEMS estimates a projected market growth for 1st level packaged Microsystems and MEMS from US$ 12 billion in 2004 to 25 billion in 2009 (Corresponds to an Annual Compound Growth Rate (CAGR) of 16%). [12] The market by application field can be subdivided into three main application fields: IT peripherals, Automotive and Consumer Electronics. IT peripherals will continue to have a big market share projected for 2009, comprising with RW heads and inkjet heads. However, the share of IT peripherals will decrease from 69% to 54% [12]. The Automotive will be a major application field with several representative application fields such as airbags, or Tire Pressure Monitoring (TPMS). The growth in the number of units will be rapid, although the revenue growth will be moderate due to the pressure on prices. Consumer electronics will experience the strongest market growth with the share in MEMS/MST markets growing from 6% in 2004 to 22% in 2009 [12]. graph 1 The Graph shows the market by application field for MEMS products. Consumer electronics will drive market growth in the next 4 years. With regard to products, 14 out of 26 MEMS/MST products are expected to exceed $100 million in revenue in 2009. Completely new products in 2009 will include micro fuel cells, MEMS memories, chip coolers, liquid lenses for cell phone zoom and auto-focus [12]. DISCUSSION AND CONCLUSION Even as market predictions vary widely, the fact remains that MEMS will continue to develop as one of the most important technologies of the 21st century. MEMS is particularly special because they are complete Microsystems on a chip that can contain moving parts, as well as optical, chemical, and electrical components. However, MEMS technology faces many challenges such as lacking advanced simulation and modeling tools for MEMS design, non-standardized packaging of MEMS devices and systems, and lack of MEMS Quality control standards. MEMS is already a successful industry though it is only at its developing stages. Current MEMS market is led by the automotive and telecommunications fields, with a focus on MEMS sensors. Biomedical and telecom industry hold the most promise for future MEMS devices. While market share and related data about MEMS may give uncertain information about the actual scale and growth of its expansion, the acceleration in development in MEMS technology, gives great hope of rapid market growth. The fusion of this technology with nanotech materials technology and biotechnology to create third generation MEMS will create new lifestyles and have a revolutionary impact on society. Efforts must be made now to establish the technical infrastructure that will enable the creation of these future devices. Thus, it can be confidently concluded that the labour force associated with and the money invested in MEMS technology will keep growing. REFERENCES 1. Guckel. H, Christenson. T. R. & Skrobis, K. J. 1993. Method of manufacturing micromechanical devices. United States Patent 5206983. Available from http://www.freepatentsonline.com/5206983.html 2. Lyshevski, S. E. 2002. MEMS and NEM: Systems, Devices, and Structures. Florida: CRC Press. 3. Guckel. H, Burns. D.W, Visser. C.C.G,'Tilmans. H.A.C & Deroo, D. 2002. Fine-grained polysilicon films with built-in tensile strain. IEEE transactions on Electron Devices[online] 35(6) [Accessed 2nd May 2008],pp.800-801. Available from World Wide Web http://ieeexplore.ieee.org/xpl/freeabs_all.jsp'arnumber=2534 4. Klaassen E.Ha, Petersen Kb, , , Noworolski J Mc, Logan Jb, Maluf N Ib, Brown Jb, Storment Ca, McCulley Wb & Kovacs G T. Silicon fusion bonding and deep reactive ion etching: a new technology for microstructures Sensors and Actuators A: Physical 52(1-3) pp 132-139 5. Pasch, N F, Mallon T G, & Franklin M A. 1996. Techniques for assembling polishing pads for chemical-mechanical polishing of silicon wafers United States Patent 5516400 Available from http://www.freepatentsonline.com/5516400.html 6. Barth P W,'Pourahmadi F,'Mayer. R, Poydock J, & Petersen K. Monolithic Silicon Accelerometer with Integral Air Damping and Overrange Protection. Solid-State Sensor and Actuator Workshop, 1988. Technical Digest., IEEE [Accessed 2nd May 2008] pp 35-38. Available from World Wide Web http://ieeexplore.ieee.org/xpl/freeabs_all.jsp'arnumber=26427 7. Hulsing R H &MacGugan D C 1993 Miniature IMU based on micro-machined Coriolis sensors. The 1993 National Technical Meeting of the Institute of Navigation; San Francisco, CA, USA; 20-22 Jan. 1993. pp. 353-360. 8. MEMS and Nanotechnology Clearinghouse. 2008.[online] [Accessed 2nd May 2008] Available from World Wide Web http://www.memsnet.org/mems/what-is.html 9. MEMS Technology. 2008. [online] [Accessed 2nd May 2008] Available from World Wide Web http://www.memx.com/technology.htm 10. MEMS/Microsystems Device and Process Technologies 2000] [Accessed 2nd May 2008] Available from World Wide Web http://www.wtec.org/loyola/mcc/mems_eu/Pages/Chapter-5.html 11. Lagouge M 2008 MEMS World - Electrostatic actuators [Accessed 2nd May 2008] Available from World Wide Web http://matthieu.lagouge.free.fr/mems/electrostatic.html 12. NEXUS market analysis for MEMS and microsystems III 2005 - 2009 2005 [Accessed 2nd May 2008] Available from World Wide Web http://www.suframa.gov.br/minapim/news/visArtigo.cfm'Ident=147&Lang=EN Read More