Physical Sensors Drive MEMS Consumerization Wave Benedetto Vigna General Manager MEMS Product Division STMicroelectronics In the past 30 years micromachined accelerometers, gyroscopes and pressure sensors were mainly used in Automotive, Industrial and Medical markets. These physical sensors were not accepted by the consumer markets for both technical and economical reasons. But the recent availability of inexpensive, ultracompact, low power consumption and multiple axis sensing devices made these products accessible to the wide consumer market. MEMS are not seen anymore as expensive jewels. This is the beginning of the MEMS Consumerization Wave with currently four main consumer applications: User interface in Game controllers and Mobile Phones Hard Disk Drives Protection Fitness Monitoring in portable devices Image stabilization in Digital Still Cameras and Camcorders But many other applications based on these physical sensors are on the horizon. STMicroelectronics is highly committed to ride the MEMS Consumerization Wave by investing in the first state-of-the-art 8 silicon manufacturing line, new product and new technology development in cooperation with selected partners. The ultimate goal is to guarantee consumer customers proper time-to-volume and time-to-market. This talk will discuss how physical sensors are driving the MEMS Consumerization Wave and the role that ST is playing and it s planning to play in the future in this market. 1. Introduction Micro-Electro-Mechanical-Systems (MEMS) are three-dimensional structures manufactured through silicon micromachining technologies. They made their first appearance in semiconductor fabs in the sixties and, among many applications, they can be used to sense acceleration, angular rate, pressure and sound pressure. Our daily life is full of micromachined physical sensors. In the car all active and passive safety systems, like Vehicle Dynamic Control and Air Bags, are using acceleration and yaw rate sensors to protect our lives. Car gasoline consumption is also very low thanks to the usage of pressure sensors in engine manifolds and fuel lines. But since few years our unconsciuos interaction with micromachiend products doesn t stop here. The portable PC we use has a 3-axis accelerometer to protect data stored in Hard Disk Drive in case of accidental fall. Several mobile phones from different brands exploit the sensing ability of tiny accelerometers to simplify the interface between the man and the equipment. Last, but not least if we play with Nintendo Wii TM or Sony PS3 TM, we can really appreciate the playing experience thanks to remote controller motion sensing feature. Sense and Simple, that s the value proposition enabled by MEMS in the consumer market in line with Naoto Fukusawa-san s dream to brake all the barriers between the man and the complex world of electronic devices. MEMS are manufactured in semiconductor fabs like the CMOS transistors we find in any electronic chip, but in this case not only electrons are moving. Silicon springs, electrodes, membranes and cantilevers are also moving. Silicon micromachined products compete quite oftenly with quartz and piezoelectric based products in price, size and performances. Most of the times they represent the best technical and economical solution for the consumer market with a clear roadmap towards miniaturization and integration. And this explains why in the last few years we saw the raise of MEMS Consumerization Wave [1,2].
Motion sensors, like accelerometers and gyroscopes, are bringing the movement detection dimension inside the silicon. Their penetration will continue to increase in the automotive market, also driven by regulations [3], but their presence in the consumer market will happen at definitely higher rate. In the best case the speed of growth of automotive MEMS suppliers has been six times smaller than STMicroelectronics growth in the consumer market. Infact, multi-axis accelerometers, once used only for active and passive safety systems in the car, are finding their space in laptops, hard-disk-drives, mobile phones, and game controllers. Besides Vehicle Dynamic Control systems, yaw rate sensors are being used to improve image stabilization in camcorders and digital still cameras. Moreover motion sensors and geo-magnetometers are expected to cluster together in Motion Measurement Units to enable personal navigation in portable devices, thus fostering the deployment of Location Based Services by telecommunication operators. Tiny pressure sensors today are widely used in the automotive and the medical markets. Their penetration will rapidly increase in automotive thanks to the Tyre Pressure Monitoring application. But recently developed thin, small and inexpensive pressure sensors will appeal also the big consumer market enabling new applications and bringing new sources of revenues to the wireless operators. Capacitive silicon microphones are also competing adequately with non-surface mountable electret-condenser microphones in mobile phone and laptop. Clustering of several sensors, like accelerometers, gyroscopes and pressure sensors, in one single module will definitely happen. And thus MEMS suppliers must be ready to listen to customer requests developing a technology platform enabling multiple sensor fusion. STMicroelectronics has already many Jisseki for two and three axis accelerometers in all the world continents and it has developed two technology platforms, THELMA TM and VENSENS TM, for sensor integration. Nowadays it s developing multiple axis gyroscopes, pressure sensors and microphones and it s also open to partnerships with companies to develop any potential sensor requested by customer, like magnetometers. Production and development activities are all running together in the state-of-the-art 8 MEMS fab so to accommodate properly the fast time-to-market required by the consumer market. 2. Micromachining Technologies for physical sensors Physical sensors interact with the physical world. They are manufactured via a process called micromachining, which shares the same processing steps derived from basic integrated circuit techniques. The end result, however, is typically a 3-Dimensional mechanical structure, most often on a silicon substrate. Nonetheless, other materials can be micro-machined or micro-formed. Among these materials are quartz, glass, plastic, and ceramic. Quartz and ceramic are used for crystal resonators and for Coriolis-based gyroscopes. Still, silicon is becoming increasingly popular thanks to its excellent electrical, mechanical and thermal properties. In addition to its excellent physical properties, silicon is extremely attractive because manufacturers can realize thousands of micro-machined components at a time on silicon wafers using proven manufacturing techniques developed for silicon chip production. Throughout its history, the worldwide microelectronics industry has cumulatively invested trillions of dollars in building up an industrial infrastructure devoted to designing and manufacturing silicon-based microelectronic devices in high volumes while continuously reducing the dimensions of transistors. Therefore MEMS can benefit from the same economies of scale that made microelectronics such a success. Moreover, since the components are made side-by-side on wafers and with an extremely wellcontrolled process, the devices can be made much more precisely and repeatably than similar products manufactured in different ways [5, 6]. Although the micron-scale of current MEMS devices mean that they can be made in older 6 wafer fabs, in the next years many companies must switch to 8 line to sustain the fast growing demand and price pressure of consumer market applications. STMicroelectronics did already this transition and thus it has a good competitive advantage versus the competition. On the technical side, the
scope and use of MEMS is primarily due to extremely small size, terrific reliability, and low power consumption, which, in many instances, allows MEMS to be capable of faster and more precise operations than their macroscopic equivalents. But the cost advantage for the customer, especially in the cosumer world, cannot be ignored. Silicon is stronger than steel and only a third of the weight; it is also brittle and not subject to plastic deformations: this is the principle of the micromachining technology. Once combined with integrated circuits, electrical signals generated by the moving structures (diaphragms and cantilevers) give perception and control capabilities to create sensors for a large variety of applications. Many micromachining processing steps are derived from basic IC manufacturing: photolithography, material deposition, reactive ion, and chemical etching. However, while the CMOS roadmap aims to pack more and more devices in plane and thickness, micro-machined devices usually have dimensions in the tenths of a millimeter and thicknesses of several tens of microns. Wet etching, grown or electroplated thick films, stacks of two/three bonded wafers, through silicon vias/holes, and high aspect-ratio dry etches are common steps for micromachining technology. Last, but not least, MEMS devices use some materials, like gold or Glass Frit, that are completely forbidden in a CMOS process. During recent decades, MEMS suppliers have been developing their own product-dedicated micromachining processes by exploiting both the processing steps they mastered and the available manufacturing assets. Although each company uses a specific micro-machining process, all of the processes can be classified into two broad classes: A. Bulk Micromachining: it is a subtractive process because a large portion of the substrate is removed to form whatever structure is desired. This technique requires less precision than surface micromachining. Thicker structures are easier to fabricate because the substrate thickness can be chosen quite freely, but the shape of the micro-machined structure is quite limited by the crystal planes of the silicon substrate. This technology is quite old and it s reaching the end of life B. Surface Micromachining: it is an additive process requiring the building up of various layers of materials that are selectively left behind or removed by subsequent processing. The bulk of the substrate remains essentially untouched. This technique was initially limited to thin devices (~2 micron), since only thin films could be deposited or grown on the substrate. However, the use of thicker films, as well as new wafer bonding techniques can help to create thicker devices. By exploiting all the tricks offered by photolithography, the manufacturing of very complex and innovative mechanical structures is fairly simple. This class of processes has longer roadmap and it s the most used for motion sensors. 3. THELMA TM and VENSENS TM Micromachining processes. STMicroelectronics currently runs in production two different micromachining processes: THELMA TM : THick Epitaxial Layer for Microgyroscopes and Accelerometers; VENSENS TM: : VENice process for SENSor. The first process is meant to manufacture high-performances and low-cost motion sensors, like accelerometers and gyroscopes, and microphones, while VENSENS TM enables the manufacturing of extremely small pressure sensors. Both micromachining processes are a proprietary combination of manufacturing steps of Bulk and Surface Micromachining technologies (Table 1). THELMA TM process begins with a standard silicon wafer onto which a layer of first oxide (~2µm) is grown for electrical isolation. A thin poly-silicon layer used for interconnections and a second sacrificial oxide (~2µm) are then deposited. Into this layer, holes are etched at the points corresponding to the supports for fixed elements and anchors for moving elements. A thicker polysilicon epitaxial layer (~15 um) is grown on top of this, and into this third layer the structures for the moving and fixed elements of the device are etched with a single mask. Finally the sacrificial oxide layer beneath the structures is removed by an isotropic etching operation to free the moving parts. The open space around the structures is filled with a gas, usually dry nitrogen, to reduce or eliminate effects caused by humidity or variations in gas density, which would affect the resonant
frequencies of the device. A second wafer is then bonded to the first one to protect the tiny structures during an injection molding process during which high pressures are applied (Fig. 1). Category IC Bulk Surface THELMA VENSENS Minimum Lithograp <0.1 3 1 0.8 0.8 hy (um) Structural N/A Mono Poly Si MonoSi Material Si Si Epipoly Sacrificial N/A Mono Si Di- Si Di- MonoSi Material Si Oxide Oxide Cleanroom Class 1/10 10 / 100 10 / 100 10 / 100 10 / 100 Wafer 8/12 4/ 6 6 / 8 8 8 Size Mask Level # > 20 8-10 > 25 8-10 8 10 Table 1: Comparison among CMOS, Bulk, Surface, THELMA TM and VENSEN TM micromachining processes. Figure 1. SEM pictures of a capacitive micro-machined structure manufactured with THELMA TM process. Fixed fingers with their anchor points are clearly visible. Moving fingers are interlocked between two fixed fingers to form variable capacitors. Wafer level capping prevents plastic to lock fingers. VENSENS TM process begins with a standard silicon wafer. A proprietary combination of wet and dry silicon etching steps enables the formation of a sacrificial layer on top of which a monocrystal silicon layer is grown. The thickness of the sacrificial layer is less than 3 µm and the thickness of the structural layer can reach 20 µm. The end result is very similar to what it s possible to get with bulk micromachining wafer to wafer bonding. But with the big advantage to have thinner, smaller and mechanically more robust chips (Fig 2). Moreover, the sealing of the cavity doesn t require any wafer-to-wafer bonding and thus the reliability of the sealing joint is definitely higher. Thanks to good electrical properties of the monocrystal silicon, good and stable resistors can be integrated in the structural layer through implantation or diffusion process. Then these resistors are connected with an aluminum metal layer to realize the four branches of a Wheatstone bridge. The bridge is sensitive to pressure changes thanks to the excellent piezoresitive properties of the monocrystal silicon layer. The metal layer is then covered with a standard dielectric, like silicon-oxy-nitride, to provide the required protection against the external corrosive agents. Figure 2. On the left a SEM picture of a cross section of VENSENS micromachined membrane; on the right side an optical picture of the top view of the pressure sensor. The square in the middle is the suspended membrane. The four piezoresistors of the Wheatstone bridge are clearly visibile at the four edges of the diaphragm.
4. Motion sensors for the consumer market. Currently, accelerometers and gyroscopes are widely adopted in the automotive market for active and passive safety systems. And they are used also in the medical market for pacemakers. Lately, they have started to penetrate the consumer market to address many new applications. The consumer market is looking for tiny, inexpensive, low voltage and low power consumption devices. Mobile phones, MP3 and MP4 players, and portable PCs are all battery operated and are becoming smaller and thinner. Moreover, the product life cycle of consumer devices is shorter than devices in automotive markets; therefore, MEMS suppliers have been tasked to develop new products much more quickly, while keeping the same level of reliability. Traditional solutions for the automotive market use big, thick, and expensive packaging such as ceramic or cavity pre-molded packages with gel. On the other hand, the consumer market prefers surface mountable packages, small, thin and low cost (Fig. 4). Full molded plastic packages (Quad Flat NoLead and Plastic Land Grid Array) for motion sensors were first introduced in 2002 by STMIcroelectronics [3] and are now widely used [12] in the industry, becoming a standard. STMicroelectronics has been miniaturizing the three axis accelerometer family at very fast pace moving from 100 mm 3 to less than 10 mm 3 packages (Fig. 3) in less than three years. Figure 3: Three-Axis Accelerometers in full molded plastic Land Grid Array packages with thickness less than 1.0 mm. On the left figure packages from 7x5mm 2, to 5x5 mm 2, to 3x5 mm 2, to 4x4 mm 2 and to 3x3 mm 2. In the automotive market, power consumption and voltage supply do not represent a big technical hurdle since they sensors not battery operated. High shock resistance is important, but it s not the same as for portable devices that might drop on the floor almost everyday. Despite these differences, for the sake of clarity, we want to emphasize that the automotive market requires a higher level of reliability in products as well as a wider operating temperature range. Figure 4: STMicroelectronics two and three axis, analog and digital, Accelerometers. In the consumer market, the supply voltage goes down to 1.8 V, and the electrical current has to be definitely lower than 1.0 ma aiming to less than 100 microampere. Additionally consumers have come to expect a power-down feature in their products as well as multiple interrupt pin functions to simplify product integration in the final equipment.
Moreover, in the consumer market, multi-axis solutions are mandatory since consumers want to activate any function from any initial physical position because, in a handheld application, there is no constant frame of reference, like in a car. Analog output is no longer sufficient and digital output is preferred for easier integration in the final product and faster application software development. However, different markets require different features, and the solution must be flexible enough to accommodate varying customer needs. And, in any case, adequate applications development tools must be easily available to the final customer. STMicroelectronics may offer both two and three axis, analog and digital, products as shown in Fig. 4 to accommodate customer requests. Each products comes with an evaluation kit and a reference design, with dedicated software for most relevant applications, is also available (Fig. 5). Figure 5. Evaluation Board (first row) and adapter boards (second row) for STMicroelectronics accelerometers. Currently, monolithic (single-chip, single-package) and hybrid (two-chips, single-package) solutions are available. Using today s technologies, it is possible to integrate the sensing element and interface together. But just because something is possible does not mean it is the best solution. Practical systems have cost and time-to-market constraints, and sometimes it is more functional and less expensive to implement complex control circuits using standard CMOS technology. A multi-chip single-package solution is not only the most cost effective, but it can also provide the modularity and flexibility needed for fast time-to-market and time-to-volume, very important for the consumer market. Figure 6: In the middle an example of a packaged 3X accelerometer inside which the two chips can be assembled side by side (right picture) or stacked (left picture) For Accelerometers and Gyroscopes, STMicroelectronics pursues the System-in-Package approach with a dual chip solution (THELMA Sensing Element and CMOS controller) in a single package. The THELMA micro-machined mechanical element, sensitive to inertia or to Coriolis force, and the analog or digital controller chip can be assembled in two equivalent configurations: side-by-side or stacked (Fig. 6). In the SiP approach, the micromachined sensor chip translates the acceleration into a differential capacitive change and an interface IC chip converts these small capacitance changes (in the range of few atto-farad) into an output signal, in an analog or digital format. Micro-machined structures are similar to those shown in Fig. 1.
Moreover, the SiP approach enables a faster development of new motion sensors like multi-axis gyroscopes. In fact, mechanical and electrical designers can re-use some of the blocks already designed and qualified for multi-axis accelerometers. Gyro-specific mechanical part and electrical IC (Fig. 7) can use the same technology platforms already in production for other multi-axis accelerometers. Companies pursuing the SiP approach can really play the LEGO TM game offering the customer the fastest and most inexpensive solution. STMicroelectronics can pick any couple of two elements from a wide collection of chips and realize fastly the final product, even adapting the pinout thanks to the Land Grid Array package configuration. Figure 7: LEGO Game rule to make a Motion Sensor: pick one mechanical element on the left side and one electrical chip on the right side, combine them in a single package you want and you get a complete accelerometer or a gyroscope. 5. Pressure sensors for the consumer market. Pressure Sensors have long been in service measuring pressure and flow in a variety of industrial, automotive and medical applications. Micro-machined pressure sensors are fabricated in Silicon with the physical sensing mechanism being either a variable resistance or a variable capacitance. The fabrication is either Bulk or Surface micromachining or a combination of the two. Standard silicon substrates or more expensive Silicon-On-Insulator substrates are equally used as a starting point. The variable resistance type uses the piezo-resistive nature of silicon to convert stress in a small diaphragm into a very small resistance change. And bulk micro-machining technology is the preferred technique. The variable capacitance type uses two parallel plates. One is fixed and the other is a thin diaphragm moving in direction orthogonal to the plane of the chip. A very small change in capacitance then occurs between these two plates. Surface micromachining methods are preferred fo these class of pressure sensors. The interface circuitry that converts resistance to voltage or capacitance to voltage can be integrated at chip level or at package level, as for motion sensors. But also in this case the System-In-Package solution guarantees faster commercialization time and higher flexibility for the customer. No ideal manufacturing process exists, but each company follows the micromaching approach that exploits better its experience and its manufacturing assets. Nonetheless the plethora of processes running in different semiconductor fabs the high-volume consumer market players had to accept the compromise related to price, size and performances of the pressure sensor. And this compromise limited strongly the wide adoption of this sensor in the consumer market. Only recently some companies found a viable solution for the consumer market. In particular, STMicroelectronics VENSENS TM technology enables the manufacturing of a Full-Silicon small (0.8 x 0.8 mm 2 ), thin (~0.3 mm) and inexpensive pressure sensor. The performances of the Full- Silicon sensor are independent on the specific package, that for classical bulk-micromachined solutions represents the biggest part of the sensor cost. And this opens the door of the consumer market definitely.
Recently STMicroelectronics patented a special package, Holed Lang Grid Array (HLGA), to exploit all the manufacturing assets already installed for the motion sensors and to offer consumer customers very small and thin packages. Fig. 8 below show a 3x3x1 mm 3 HLGA package with sensing element stand-alone (Left) and a 5x5x1 mm 3 HLGA package including two chips inside, the sensing membrane and the related electronic chip. Figure 8: HLGA 3x3x1 mm 3 pressure sensor withouth amplification and compensation IC, before and after injection molding (First Row); HLGA 5x5x1 mm 3 complete pressure sensor after die attach and wire bonding on BT substrate (second row, left picture) and after injection molding and singulation (right picture) This solution is also high shock mechanical compliant and thus it s able to withstand all the potential mechanical shocks that the sensor could experience in a portable device, like a mobile phone or personal navigation device. 6. Identified Consumer Applications for Motion Sensors and Pressure Sensors A. Sense and Simple for Mobile Phone, Game Controller, Mouse and 3-Dim Pointer. Mobile Phone The combination of micro-machined accelerometers and the appropriate application software eliminates the need for conventional switches or button and thumb wheels for scrolling, zooming and panning of web pages, e-books, and spreadsheets. This is an innovative way to solve the wellknown small button big finger problem that plagues many users. In fact, while small cell phones are convenient and easy to carry, their small display screens and limited graphic capabilities reduce the total user experience. The sensor can detect basic human movements and use them as the input for display orientation, which in turn simplifies how the user views the downloaded pages. The user can then navigate through web pages or pan through maps by simply tilting the device in the desired direction. Remote Game Controller A user-friendly interface is very attractive for gaming in portable devices, and it is a must for any company targeting the teenage market. By making the motion of the hand become the mouse for handheld devices, single-handed operations and gesture recognition can be added to gaming devices. Accelerometers allow this easy-to-use interface by sensing hand/fingers/wrist motion and translating that motion to an action in the game. Nintendo Wii TM is one of the most successful examples of this usage in the market. Mouse and 3-Dim Pointer A computer mouse is the most common interface between a person and a computer or any computer-controlled device. Hand movement across a single plane or two-dimensional surface is used to control a cursor or pointer or to activate a particular task. To this end, a typical mouse contains a two or three buttons for entering commands as well as a communications interface for connecting with the computer system. In this application, inertial sensors can be a good alternative to the optical solution, which suffers from high power consumption especially in a wireless solution. A user-controlled device accommodating an accelerometer can detect 3-dimensional movements
and send corresponding control signals to an electrical appliance such as a computer system. Combination of gyroscopes and accelerometers enhances equipment performances while enriching user experience and usability. B. Small and Safe for Hard Disk Drive Free. In Hard Disk Drive based devices like MP3 and MP4 players, laptops and mobile phones, camcorders and digital still cameras, the use of three-axis accelerometers can help protect the HDD from any potential loss of stored data in case of freefall. Three-axis accelerometers, once located on the device s board, guarantee freefall protection along all three axes (x, y, z). In fact, if the computer falls, the accelerometer senses the zero-gravity, and the dedicated microcontroller signals the read/write head to park away from the sensitive disks, before the head could crash onto the disk causing the loss of data or possibly damage the drive. C. Pedestrian Navigation for Location Based Services Portable and vehicle navigation systems use GPS receivers to determine position and provide route guidance. With any GPS system, the signal reception is not always 100% reliable. In urban areas where GPS signals are blocked due to underground tunnels, bridges and skyscrapers, accurate navigation becomes difficult. In this context, micro-machined motion sensors can assist and substitute for the GPS. If there is signal loss, a dead reckoning system continues tracking movements when satellite signals are not visible or where they are not sufficiently accurate. Furthermore, to implement dead reckoning, it is necessary to know the distance and direction travelled. Therefore, a motion measurement unit, including an accelerometer, a gyroscope, and often a magnetometer, is needed. It is important to note that because battery-operated GPS devices consume a lot of power, dead reckoning is a vital feature enabled by low-power motion sensors. D. Pedometer Pedometers are used to measure burnt calories, the speed and distance travelled by an individual on foot. For this application, an accelerometer detects the motion of a walking person. Specifically, the accelerometer output is a periodic signal describing the vertical plane motion. The wireless pedometer can be worn on the shoe and communicate with another personal device such as a stopwatch, that would then display its measurements and provide athletes with a complete training tool. Pedometers represent also an important building block for personal navigation devices and they start to be integrated in MP3 players and media phones. E. Weather Station and Altimeter Pressure sensors are meant to allow the integration of weather station in portable handsets and to assist GPS devices in altitude tracking of the end-user. So, when dialing emergency numbers, like 911 in United States, the GPS and the pressure sensor will automatically signal the position and the floor of the building where the end-user is. F. Image Stabilization in Camcorders and Digital Still Cameras. Currently, piezoelectric vibrating gyroscopes are used for image stabilization in camcorder and digital still cameras. Silicon micro-machined gyroscopes offer the advantages of reduced dimensions and lower power consumption. Moreover, they can measure angular rate along pitch and roll axes simultaneously and can be integrated more easily with other motion sensors. The increasing number of mobile phones with cameras represents a market opportunity of several hundreds million device per year, considering that currently 80% of the mobile phones have a camera. 7. New emerging application for MEMS Previous section describes only well identified consumer applications while many others are still on the horizon. MEMS suppliers must focus on miniaturization and multi sensor clustering to address properly customer requests. On one side STMicroelectronics is pursuing device miniaturization as shown in Fig. 3, on the other side it structured it s technology platform and device roadmap to enable sensor fusion in custom and standard packages (Fig. 9). In this direction HLGA and classical LGA packages are fully compatible and they are fully compatible.
Figure 9: Multi sensor module comprising 3-axis accelerometers, 3-axis gyroscopes, pressure sensors, magnetic sensors and other technologies. Schematic Block Diagram (Left Side Drawing) and an example of sensor module in MMC format (Right Side Picture) Moreover, many companies and research centers are actively working in the field of Wireless Sensor Networks [7]. It s hard to predict the market success of these applications since some technological hurdles still exist for a big volume take-off. However, it s clear that all the applications could benefit from the tiny and low power micro-machined sensors that companies are developing now for the consumer market. The MEMS of the Consumerization Wave with these new applications could literally generate a MEMS Tsunami. This is already the case of the tire pressure monitoring system, a simple 5-nodes wireless sensor network. The system is already on the market, and it relies on a micro-machined pressure sensor and acceleration switch. Other motes - wireless sensor modules consisting of some combination of a sensor, controller, receiver, battery and antenna (Fig.10) - are now yielding commercial results. The potential market for motes is limited only by the imagination. Once certain technical challenges are overcome, motes will ultimately become a regular part of our lives. They could, for example, find many applications in consumer markets, with solutions ranging from security and bio-detection to building and home automation, industrial control, pollution monitoring, and agriculture. Also, rising concerns for safety, convenience, entertainment and efficiency factors, coupled with worldwide government mandates, could boost sensor usage to unprecedented levels, although not all of them necessarily silicon micro-machined [8, 9]. In fact, motes will have to measure real-world variables like pressure, temperature, heat, flow, force, vibration, acceleration, shock, torque, humidity, strain, and images. Some of them will use micro-machined solutions while others will use conventional sensors that have been available for decades. MEMS suppliers must be ready to integrate different technologies in a modular format and that s the reason why STMicroelectronics invested in 8 state of the art fab and it setup manufacturing process platforms aimed to enable the high volume manufacturability of Motes. Figure 10: Miniaturized wireless sensor node from IMEC Research Center, Belgium. 8. Conclusions The MEMS industry will continue to provide products that enable new applications in the emerging Consumer market, but also in other markets. Currently, we are living in the commercial era of MEMS Consumerization where microphones, motion and pressure sensors are the main actors. I
believe that this trend will continue for the next five yers. And the endless new applications of Wireless Sensor Networks, today noy yet well identified, could bring us to a MEMS Tsunami literally. We are only at the dawn of this new phase and we ll see alltogether. STMicroelectronics is positioned to be an important player in this industry leveraging it s big manufacturing infrastructure, its penetration in the consumer market, its speed in execution and its wide and consolidated technology platform. References 1. B. Vigna, More than Moore: micro-machined products enable new applications and open new markets, Invited Talk, IEDM 2005, Washington D.C. Dec 2005 2. P.Adrian, Sensor Business, Marketing and Technology Developments, Sensor Business Digest, Nov 2003. 3. T. Goernig, Sensors for Active and Passive Safety systems, AMAA 2007 4. www.st.com 5. A. Borruto, Meccanica della frattura, Cap. 6, Hoepli. 6. B. Murari, Bridging the gap between the digital and real worlds: the expanding role of analog interface technologies, ISSCC 2003, San Francisco, Feb. 2003, plenary 1.3. 7. B. Murari, Lateral Thinking: The Challenge of Microsystems, Transducers 2003, Boston, invited talk. 8. R. Allan, The future of sensors, Electronic Design, July 2005. 9. R. Allan, Wireless Sensors land anywhere and everywhere, Electronic Design, July 2005. 10. IEEE Wireless Communications, Wireless Sensor Networks, December 2004, Vol. 11, No. 6 11. S. Yakushiji, Robot pets offer comfort to the elderly, The Asahi Shimbun, Sep. 17-18, 2005. 12. T. Makimoto and T.T. Doi, Chip technologies for Entertainment Robots present and Future, Invited Talk, IEDM 2002, San Francisco, Dec. 2002. 13. J. Israelsohn, Newton s chips: low-g accelerometer ICs, EDN, Jan. 2005. 14. H. Geitner, Accelerometers decrease power consumption and increase reliability of washing machines, IATEC, Chicago, March 2006. 15. B. De Masi, A. Villa, A. Corigliano, A. Frangi, C. Comi, M. Marchi, On-chip Tensile test for Epitaxial Polysilicon, Proceedings of MEMS, Maastricht January 2004. 16. F. Carli, R. Cambie, C. Combi, B. Vigna, Polysilicon Failure Stress and Young s modulus evaluation in MEMS devices Proceedings of IMECE 2003, Washington November 2003. 17. B. Vigna, MEMS Dilemma: How to move MEMS from the Technology Push category to the Market Pull category, Proceedings of TSA, Taipei October 2003 18. B. Murari and B. Vigna, System-on-Chip morphs into Lab-On-Chip: Current and future Products, Proceedings of FAST, Milan May 2001