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- 1. 1 KHUSHI RAM BHARDWAJ EE 4TH YEAR 359/07 DAVIET(JALANDHAR)
- 2. Introduction Electromechanical Systems MEMS Current Applications NEMS and Nanotechnology Impact of Miniaturization Challenges and Possibilities References 2
- 3. MEMS IS SIMPLY KNOWN AS MICRO ELECTRO MECHANICAL SYSTEM.IT IS THE ART OF MINIATURIZING.MINITUARIZING ART WAS VERY OLDLY USED BY WATCH MAKER IN 13TH CENTURY. 3
- 4. 4 Figure 5.1: Jonathan Swift.
- 6. MST - Microsystems Technology . MEMS - Microelectromechanical System. Manmade devices created using compatible microfabrication techniques that are capable of Converting physical stimuli, events and parameters to electrical, mechanical & optical signals Performing actuation, sensing and other functions 6 Definition and Terms
- 7. 7
- 9. Materials Crystallography – Forms of Silicon Amorphous Polycrystalline Crystalline “Miller Planes” 9 MEMS Microstructure Fabrication
- 10. Pattern definition Photolithography Deposition Oxidation, chemical-vapor deposition, ion implantation Removal Etching, evaporation 10 -Structural layer -Sacrificial layer deposit pattern etch Microstructure Fabrication, Continued
- 11. 11 MEMS Advantages The advantages of MEMS devices include • Size • High sensitivity • Low noise • Reduced cost The applications for MEMS are so far reaching that a multi-billion dollar market is forecast. Key industry applications include transportation, telecommunications and healthcare.
- 12. Accelerometers Micro Optical Electro Mechanical Systems (MOEMS) Digital Mirror Devices (DMD) used in Projection Devices Deformable mirrors Optical Switches Inkjet Print heads (Microfluidics) Pressure Sensors Seismic Activities - Thermal transfer 12 Current Applications
- 13. Micro-arrayed biosensors Virus detection Neuron probes (nerve damage/repair) Retina/Cochlear Implants Micro Needles µChemLab Micro Fluidic Pumps - Insulin Pump (drug delivery) 13 Biomedical Current Applications, Continued
- 14. Hand held detectors – biological & chemical microsensors µChem’s Lab on a Chip (security applications) Data Storage Systems IBM Millipede storage system – AFM tip writes data bit by melting a depression into polymer mediaum and reads data by sensing depressions. 14 Detection systems Current Applications, Continued
- 15. Nanotechnology manipulation of matter at the nanometer scale. Nanomaterials Started with carbon. Behavior depends on morphology. 15 carbon and carbon nanotube NEMS and Nanotechnology
- 16. Quantum dots Nanowires Quantum films 16 Quantum Dots. NEMS and Nanotechnology, Continued
- 17. 17 • Electrostatic manipulation • Moving one electron or molecule at a time • Patterning • Dip Pen Lithography • Electron Beam Lithography Nano Fabrication NEMS and Nanotechnology, Continued
- 18. 18 Cantilever Sensors Mass Storage (IBM) Millipede chip Nanochip Molecular Electronics Transistors Memory cells Nanowires Nanoswitches Merging of technologies
- 19. 19 Cantilever sensors are essentially MEMS cantilevers with chemical arrays attached. The cantilevers, acting much like tuning forks, have a natural frequency of vibration which changes as more mass is attached (nano function). The change in frequency is sensed by the MEMS device indicating a measurable presence in the system of particular reacting compound. Selective chemical layer Reacting compound cantilever Cantilever sensor Merging of technologies NEMS and Nanotechnology, Continued
- 20. Potential Positive Impacts Reduction of disease. Job opportunities in new fields. Low-cost energy. Cost reductions with improved efficiencies. Improved product and building materials. Transportation improvements Potential Negative Impacts Material toxicity Non-biodegradable materials. Unanticipated consequences. Job losses due to increased manufacturing efficiencies. 20 Impact of Miniaturization
- 21. Fundamental and applied research Engineering and technological developments Low Cost Fabrication “Molecular manufacturing” 21 Challenges and Possibilities
- 22. Gad-el-Hak, M. MEMS, Design and Fabrication, Second Edition. (2005) Lyshevski, S., MEMS and NEMS, CRC Press LLC. (2002) Maluf, N. and Williams, K., An Introduction to Micromechanical Systems Engineering, Second Edition, Artechouse, Inc. (2004) Microsytems, Same-Tec 2005 Preconference Workshop, July 25 &26, 2005. Taylor and Francis, MEMS Introductory Course, Sandia National Laboratories, June 13-15, 2006. What is MEMS technology? MEMS and Nanotechnology Clearinghouse. http://www.memsnet.org/mems/what-is.html. 22
- 23. 23
Notas do Editor
- MEMS AND NEMS Last updated: February 6, 2008. Biography of Dr. Arunachala Nagarajan: Arunachala (Raj) Nagarjan received his Bachelors and Masters degree in Electronics from the University of Madras, India and later his M.S. and PH.D degrees from Carnegie Mellon University in Pittsburgh, Pennsylvania. After his graduation he worked for IBM for almost 30 years in different aspects of semiconductor chip and packaging technologies in both technical and management positions. He then was Vice President for SRM Systems and Technology, Boston. Presently he is teaching semiconductor technology at Austin Community College. He holds almost 30 patents and an equal number of publications.
- Topics.
- Introduction: Micro-ElectroMechanical Systems (MEMS) and Nano-Electro-Mechanical Systems (NEMS) rely on technologies of miniaturization. Watch makers have practiced the art of miniaturization since the 13th century. With the invention of the compound microscope in the 1600’s and later use to observe microbes, plant and animal cells and modern day, atomic force and electron microscopes that allow for observation at the molecular and atomic scale, there has been an interest to manipulate matter at a smaller and smaller scale. One success story has been the miniaturization of the modern era’s transistor which has allowed for the development of ever smaller and more powerful gadgets and machines. The transistor in today’s integrated circuits has a size of 0.18 micron in production and approaches 10 nanometers in research laboratories. MEMS and NEMS represent a fundamental breakthrough in the way materials, devices, and systems are understood, designed, and manufactured. Utilizing a combination of microelectronics processes developed within the semiconductor industry and available bulk microfabrication techniques, mechanical elements such as sensors, cantilevers and actuators used to sense and manipulate the environment are combined with the needed electronic circuitry to control the miniature device. MEMS usually combine electrical properties with mechanical structural components at the micrometer scale to produce devices capable of performing tasks impossible using conventional technologies. For NEMS, the unique properties and behaviors of matter displayed at the nanometer scale have yet to be fully understood or exploite
- Introduction, Continued: The Scale of Things: Today’s semiconductor technology aims at the 45 nanometer scale for circuit devices, several thousand times smaller than the diameter of human hair. Another way of looking at micro and nano technology is from the perspective of processing. The micro world is all top down fabrication using micro-miniaturization technologies and bulk processing while the nano world is bottom up fabrication and uses self assembly processes. Fig. 5.2 - http://www.nano.gov/html/facts/The_scale_of_things.html.
- Introduction, Continued: Definition and Terms: Unlike the European term MST, the U.S. term MEMS applies to systems which include a moving part and some form of electronics. Alternately, MEMS, also known as Microelectronic Mechanical Systems, can be described as the integration of mechanical elements, sensors, actuators and electronics on a common silicon substrate through micro fabrication technology. While the electronics portion is manufactured using integrated circuits (IC) process sequences, the micro mechanical components are fabricated using compatible “micromachining” processes that selectively etch away parts of silicon wafer or add new structural layers to form the mechanical and electromechanical device. The broadest requirement for these very small devices is ability to sense the environment, to collect necessary data and to create a signal or action to make desired changes to the environment. References: Same-Tec 2007. Southwest Center for Microsystems Education. Regional Advanced Technology Education Center. http://www.scme-nm.org/.
- Introduction, Continued: The image shown provides an example of the scale of micromachines created with MEMS technology. Visit Sandia National Laboratories website on Micromachines at http://mems.sandia.gov/ for additional images and information on the technology and areas of focus. Fig. 5.3 - http://mems.sandia.gov/scripts/images.asp. Courtesy of Sandia National Laboratories, SUMMiTTM Technologies, www.mems.sandia.gov.
- Electromechanical Systems: Functional Block Diagram: Electromechanical systems fall into three groups - the conventional electromechanical systems, micro electromechanical systems (MEMS) and Nanoelectromechanical systems (NEMS). In the first two systems the behavior can be analyzed by fundamental theory of electromechanics (classical mechanics and electromagnetism). For nanoelectromechanical systems (NEMS), quantum physics is needed to describe the operational parameters of the devices. Fig. 5.4 - ACC Instructional Development Services.
- MEMS: Microstructure Fabrication: Traditionally MEMS have relied upon silicon and silicon based materials, though other materials like silicon dioxide, silicon nitride, and silicon on insulators (SOI), gallium arsenide, quartz, glass, and diamond have also been explored. Silicon, polysilicon, and amorphous silicon are the most common materials currently used in MEMS commercial production. In silicon-based MEMS processing, many of the features of integrated circuit processing along with micromachining techniques are used. Silicon has very valuable properties which lend itself well to micromachining. Because of its natural abundance and versatility, it is also an economically desirable element in commercial applications. Crystallography is the study of crystal structure which affects the electrical, mechanical, and optical properties of materials. The crystal planes indicated by Miller indices affect the etching rates and thus help to create different structural forms. Wet etching of silicon crystals allows the creation of micro-channels, micro nozzles, micro chambers, and alignment targets. There are different forms of silicon: Amorphous - No predictable long range atomic order; no clear or well defined band gap, electronic properties affected. Polycrystalline - Long range order; solid consists of many small crystals ‘stuck’ together; distinct band gap. Crystalline - Extremely long term order with few defects; little difference in the placement of the atoms throughout solid; well-defined band gap, a sharp transition from valence band to conduction band with no tailing. Miller Planes are represented by (x, y, z) where the {x, y, z} planes are perpendicular to the corresponding vectors. Miller inices affect etching rates and help to create different structural forms. The common orientations are indicated in the diagram. Anisotopic wet etching of silicon crystals allows for the creation of micro-channels, micro-nozzles, micro chambers and the alignment targets needed for micro devices. Fig. 5.5 - http://en.wikipedia.org/wiki/Image:Indices_miller_direction_exemples.png.
- MEMS, Continued: Microstructure Fabrication, Continued: The basic operations for building microstructures are pattern definition, deposition and the removal of unwanted material. Micromachining techniques are used to produce wells or channels in a prepared substrate by means of selective etching. The bulk micromachining manufacture of micro devices generally uses top-down fabrication techniques of etching deep into prepared silicon wafers to create three-dimensional MEMS components. These techniques utilize etchants like KOH that etch different crystallographic directions at different rates. This helps to make vee grooves, pyramids and channels suited for production of microsensors and accelerometers. The structures are formed using orientation-independent isotropic etching and orientation-dependent anisotropic etching (KOH & DRIE). Fig. 5.6 - ACC Instructional Development Services.
- MEMS, Continued: MEMS Advantages.
- Current Applications: Microsensors have proven to be of great commercial value. Examples include pressure sensors, strain gauges, accelerometers, and gyroscopes. MEMS accelerometers are quickly replacing conventional accelerometers for crash air bag deployment systems in automobiles. MEMS accelerometers are much smaller, more functional, lighter, and more reliable and are produced for a tenth of the cost of the conventional macro-scale accelerometer elements. Optical MEMS devices range from bar code readers to fiber optic telecommunication and use a range of wide band-gap materials, nonlinear electro-optic polymers, and ceramics. A well established commercial example of an optical MEMS device is the Digital Light Processor (DLP) by Texas Instruments used for projection displays. Deformable mirrors are used for image enhancement systems including imaging the retina of the eye. Computer hard drives have a MEMS device accelerometer that senses rapid motion and parks the head to avoid damaging the surface during a fall, the iPhone uses one to automatically rotate the display as the phone is rotated by the user.
- Current Applications: Biomedical: This is where rapid strides of development are happening in MEMS device applications. The key areas of applications are biomedical instruments and analysis and implants and drug delivery. MEMS have special applications in these activities because of smaller size, reduced cost, less intrusive surgical procedures, reduction of the amount of test samples needed, speed of diagnosis, and patient recovery time. MEMS pumps can trigger subcutaneous infusion of insulin for diabetes patients and the device is small enough to be worn directly on the skin for real time glucose monitoring. Other applications include DNA testing, drug delivery, and blood testing. Miniaturized implants for the replacement of the retina and the ear drum are also on the market. Purdue researchers created a device that detects the mass of a single virus particle. The device naturally vibrates at a specific frequency. When a virus particle weighing about one –trillionth as much as a grain of rice lands on the cantilever it vibrates at a different frequency. The next step is to coat a cantilever with the antibodies for a specific virus that attracts certain viruses that could make it possible to create detectors to specific pathogens.
- Current Applications, Continued: Detection systems.
- NEMS and Nanotechnology: A nanometer is a billionth of a meter. The prefix nano is Greek for dwarf. The diameter of human hair is approximately 100,000 nanometers. A red blood cell is approximately 10,000 nanometers. Nanotechnology is the manipulation of matter at the nanometer (10-9m) scale. It involves the control of molecules at an atomic level to create materials with unique properties. The mechanical strength and electronic and optical properties of many materials can be altered at this scale. Carbon, which is in the same periodic column as silicon, is an important element in nanotechnology. Carbon is known for forming stable and strong covalent bonds. In short chains it has the properties of gas, in medium chains, a liquid, and in long chains it can be a solid like plastic. In diamond carbon atoms are stacked in a three dimensional array or lattice structure. The carbon nanotube is a sheet of carbon chains rolled with a seamed edge. These are self assembled carbon nano structures and can be either single walled or multi-walled. Carbon nanotubes have very high tensile strength - 100 times greater than steel. They are elastic, light weight, and display thermal conductivity (10 times silver). Carbon nanotubes can occur naturally (as soot). They possess metallic and semiconducting electronic behavior depending on chirality or handedness of the atomic arrangment. The structural density of carbon-based integrated circuits exceeds the density of integrated circuits developed using conventional silicon based technologies by a thousand-fold. Fig. 5.8 - http://en.wikipedia.org/wiki/Image:Eight_Allotropes_of_Carbon.png.
- NEMS: Quantum dots, Quantum wires, and Quantum Films: As the size of structures becomes smaller and smaller, matter at the nanoscale exhibits novel electrical and structural characteristics due to the dominance of quantum effects and to the confinement of electrons and holes in these small dimensions. The number of directions free of confinement is used to classify structures, thus 2D confinement is a quantum film, 1D confinement is a quantum wire, and 0D of confinement is a quantum dot. Quantum Dots are particularly significant in optical applications; electronically they act like single-electron transistors and display the Coulomb blockade effect. Nanowires, also known as “quantum wires”, could be used to link tiny components, including chemical compounds, into extremely small circuits. There are many different types of nanowires - metallic (e.g., Ni, Pt, Au), semiconducting (e.g., Si, InP, GaN, etc.), and insulating (e.g., SiO2,TiO2). Repeating organic (e.g. DNA) or inorganic (e.g. Mo6S9-xIx) units make up molecular nanowires. Depending on the material composition, there are several methods available to make nanowires, the most common being Vapor-Liquid-Solid (VLS). References: Nanowire. (2008, January 27). In Wikipedia, The Free Encyclopedia. Retrieved 04:36, February 5, 2008, from http://en.wikipedia.org/w/index.php?title=Nanowire&oldid=187143934. Fig. 5.9 - ACC Instructional Development Services.
- NEMS and Nanotechnology, Continued Nano Fabrication: Electrostatic manipulation – The Scanning Tunnel Microscope (STM) can be used to make atoms slide over a surface in order to move them into a desired arrangement by electrostatic forces. Resolution is effectively the size of a single atom but the process is exceptionally time consuming and requires special conditions to prevent movement of atoms out of place. STM can also be made to write on a chemically charged electron beam resist. Pattern Electron Beam Lithography - Surface micromachining can be conducted at the nanoscale using electron beam lithography to create free standing or suspended mechanical objects. An electron beam is for scanning a desired pattern in the resist. Dip pen lithography uses an atomic force microscope (AFM) probe tip to deposit a layer of material onto a surface, much as a pen writes on paper. A pattern can be drawn on a surface using a wide range of “inks” such as thiols, silanes, metals, and biological micromolecules. This technology can be used in biosensor fabrication. Self Assembly - The self-assembly of molecules is a favored mechanism at the nanoscale as it relies on natural forces to create highly perfect assemblies. Snow flakes, salt crystals and soap bubbles are all examples of self assembly. Simply controlling environmental conditions and molecular components may provide for a very cost efficient manufacturing scheme.
- NEMS and Nanotechnology, Continued: Merging of technologies: NEMS technology is still in its infancy with global research and development actively under way. Many of the NEMS device technologies use MEMS as a bridge to the nano-world. We are already dealing with matter on the nanoscale in a technology that most of us take for granted, hard disc drives. The biosensor is a unique blend of the ability for biology to identify individual types of molecules in complex mixtures with the speed, convenience, and low cost of microelectronics. MEMS will provide a bridge to enable the applications of nanotechnology as illustrated in the cantilever sensor.
- NEMS (Nanotechnology meets MEMS) A typical example is the cantilever sensors used to detect a single E. Coli cell or the detection of a single DNA strand. The atomic force microscope used in this technique has a tip made of silicon using a typical MEMS device process and is of micron dimensions. Cantilever sensors recognize resonant frequency shifts with the addition of mass thereby indicating the presence or absence of specific compounds in the environment tested. These type of sensors have been used to detect the presence of a single E. coli organism and a single DNA strand. References: Waldrop, M.M. and Lippel, P. The Sensor Revolution A Special Report. (March 22, 2005) The National Science Foundation. http://www.nsf.gov/news/special_reports/sensor/overview.jsp. Fig. 5.10 – ACC Instructional Development Services.
- Impact of Miniaturization: The impact of MEMS and NEMS on our future lives will be tremendous. These emerging technologies open up entirely new job opportunities both in semiconductor and biological applications. MEMS and nano manufacturing is a logical transition from today’s semiconducting manufacturing methods and will lead to numerous teaching and manufacturing jobs. The biological and optical applications of MEMS and NEMS will open up applications, development, and research. There is an incentive for research in several universities and many government and privately-funded initiatives are in place to create better products with nanotechnology. MEMS and NEMS will likely greatly improve the construction and transportation industries as vehicles and building materials become lighter, stronger and more durable and incorporate greater fuel efficiencies. Unfortunately the effects of MEMS and NEMS on our environment are not currently well understood. Carbon based NEMS may be more toxic than conventional systems. Some of the NEMS may contain heavy metals and may be small enough to avoid detection by the body’s immune system , causing damage against which there is no defense. The NEMS constituent materials may be extremely toxic to living organisms potentially hindering DNA mechanics and protein synthesis. They may also be non-biodegradable which would result in chronic toxicity. Nanomaterials may be inadvertently introduced into the environment and make their way into the food chain. Self replicating nano robots may cause serious problems. It is important to invest more time and money to research the potential dangers of nanotechnology. Just like semiconductors changed the lives in the 20th century, MEMS and NEMS have the potential to change human lives in the 21st century.
- Challenges and Possibilities: The level of activity in MEMS and NEMS is rapidly expanding. There was only one program in the 1960s, now there are at least 40 centers in the U.S. and a hundred centers worldwide devoted to micro- and nanotechnological advancements. In 2007, there were at least 15 firms worth over $100 million in the industry. There are at least 10,000 MEMS-related patents. Microsystems serve almost all industries like aerospace, information technology, automotive industry, defense industry, medical industry, the data projection industry, telecommunications, chemical, oil, gas and many others. The complexity of phenomenon and effects in MEMS and NEMS processing requires new fundamental and applied science as well as engineering and technological developments. High fidelity modeling will most likely be required. Developing high-yield, low-cost fabrication techniques will be essential. To fabricate nanoscale structures, device and systems molecular manufacturing methods and technologies must be developed and enhanced. The challenges in MEMS and NEMS will be the reliability of the products and packaging. Computational models need to be developed to design, test and predict the behavior of MEMS and NEMS as they work together. The packaging of MEMS and NEMS pose unique problems and lot of work has to be done to understand the reliability exposures and to develop the appropriate corrective procedures in product development and manufacturing. Finally, bottoms-up self-assembly techniques are still in their infancy . Concentrated efforts should be undertaken to make it a more viable manufacturing technique as it holds the greatest promise in our nanoscaled futures.
- References: Gad-el-Hak, M. MEMS, Design and Fabrication, Second Edition. (2005) Lyshevski, S., MEMS and NEMS, CRC Press LLC. (2002) Maluf, N. and Williams, K., An Introduction to Micromechanical Systems Engineering, Second Edition, Artechouse, Inc. (2004) Microsytems, Same-Tec 2005 Preconference Workshop,, July 25 &26, 2005. Taylor and Francis, MEMS Introductory Course, Sandia National Laboratories, June 13-15, 2006. What is MEMS technology? MEMS and Nanotechnology Clearinghouse. http://www.memsnet.org/mems/what-is.html.