dokumen.tips_mems-technology-55846320a5038.ppt
- 1. Presented by: MADHINA BASHA (10331D5708) MEMS TECHNOLOGY Under the guidance of: Mr. V.N.LAKSHMANA KUMAR, M.Tech Assistant professor, ECEdept.
- 2. CONTENTS 1. Abstract 2. Introduction 3. What are MEMS? 4. MEMS Vs. IC’s 5. MEMS and IC’s 6. MEMS Market Opportunities and Outlook 7. Integration of MEMS with Electronics 8. Applications 9. Conclusion and Future Scope 10. References
- 3. ABSTRACT Micromachined Electro-Mechanical Systems (MEMS), also called Micro fabricated Systems(MS), have evoked great interest in the scientific and engineering communities. When MEMS devices are combined with other technologies new generation of innovative technology will be created. By using such technologies wide scale applications are being developed every day. MEMS technology has enabled us to realize advanced micro devices by using processes similar to VLSI technology. The material properties at the micron scale show that silicon is eminently suited for micromechanical devices and therefore it shows the possibility of integrating MEMS with VLSI electronics. Process design, development and integration to fabricate reliable MEMS devices on top of VLSI-CMOS electronics using two “Post- CMOS” integration approaches will be presented.
- 4. INTRODUCTION The term MEMS first started being used in the 1980’s. It is used primarily in the United States and is applied to a broad set of technologies with the goal of miniaturizing systems through the integration of functions into small packages. The fabrication technologies used to create MEMS devices is very broad based. MEMS has been identified as one of the most promising technologies for the 21st Century. It has the potential to revolutionize both industrial and consumer products by combining silicon-based microelectronics with micromachining technology. If semiconductor micro fabrication was seen to be the first micro manufacturing revolution, MEMS is the second revolution.
- 5. Micro-Electro-Mechanical Systems (MEMS) are micron-scale devices that can sense or manipulate the physical world. MEMS are usually created using micromachining processes (surface or bulk micromachining), which are operations similar to those used to produce integrated circuits (ICs) devices. MEMS are separate and distinct from the hypothetical vision of molecular nanotechnology or molecular electronics. MEMS are made up of components between 1 to 100 micrometers in size (i.e. 0.001 to 0.1 mm) and MEMS devices generally range in size from 20 micrometers (20 millionths of a meter) to a millimeter. What are MEMS?
- 6. Like IC’s previously, MEMS is moving away from discrete components to integrating the mechanical device with electronics, photonics and fluidics in an integrated system. MEMS will play a vital role in the emerging integration of ICT (Information Communications Technology) markets with biomedical, alternative energy and intelligent transportation. In addition to sensors, we believe other areas with high growth potential for MEMS in the next coming years. MEMS can use or reuse mature process equipment obsolete for ICs.
- 8. MEMS Vs. IC’s One way to look at it: IC’s move and sense electrons MEMS move and sense mass Another: IC’s use Semiconductor processing technologies MEMS can use a variety of processes including Semiconductor but also Bulk, LIGA, Surface Micromachining… Packaging IC packaging consists of electrical connections in and out of a sealed environment MEMS packaging not only includes input and output of electrical signals, but may also include optical connections, fluidic capillaries, gas channels and openings to the environment. A much greater challenge.
- 9. MEMS and IC’s IC’s IC’s are based on the transistor – a basic unit or building block of IC’s. Most IC’s are Silicon based, depositing a relatively small set of materials. Equipment tool sets and processes are very similar between different IC fabricators and applications – there is a dominant front end technology base. MEMS Does not have a basic building block – there is no MEMS equivalent of a transistor. Some MEMS are silicon based and use sacrificial surface micromachining (CMOS based) technology, hybrids, some are plastic based or ceramic utilizing a variety of processes – Surface & bulk micromachining, LIGA, hot plastic embossing, extrusion on the micro scale etc. There is no single dominant front end technology base but emerging and established MEMS applications have started to “self-select dominant front- end technology pathways” (MANCEF 2nd Roadmap).
- 10. MEMS Market Opportunities and Outlook While the MEMS market has only started to achieve wide-spread notice during the current decade, its first commercial success dates back to the late 1960s. The four areas of initial major MEMS commercial success are: Pressure sensors Accelerometers Optical micro-mirrors Inkjet nozzles The initial demand markets for MEMS are: Military/Aerospace Automotive Medical
- 11. The MEMS market however, is still in the nascent stages of its life cycle and consequently is expected to enjoy much higher growth over the next decade as MEMS applications continue to broaden and proliferate.
- 12. The ultimate size of the MEMS market will be dependent on whether the industry can evolve from the “one product, one process” model that has characterized it to date. A estimation by Kurt Petersen shows MEMS complexity to be about a decade behind that of microprocessors and that, until the mid-1990s, it was about 20 years behind.
- 13. The initial MEMS penetration of mass consumer markets has led to increasing wafer-level packaging and multi-function integration, which are starting to push MEMS into the price/performance escalations of more traditional mass semiconductors. This trend has also led to better integration with CMOS chips resulting in System-in-a-Package (SIP) solutions which are particularly important for space constraint applications such has cell phones and other mobile devices.
- 14. Integration of MEMS with Electronics The decision to merge CMOS and MEMS devices to realize a given product is mainly driven by performance and cost. On the performance side, co-fabrication of MEMS structures with drive/sense capabilities which control electronics is advantageous to reduce parasitics, device power consumption, noise levels as well as packaging complexities, yielding to improved system performance. With MEMS and electronic circuits on separate chips, the parasitic capacitance and resistance of interconnects, bond pads, and bond wires can attenuate the signal and contribute significant noise
- 15. On the economic side, an improvement in system performance of the integrated MEMS device would result in an increase in device yield and density, which ultimately translates into a reduction of the chip’s cost. Moreover, eliminating wire bonds to interconnect MEMS and ICs which gives lower manufacturing cost. However, in order to achieve high performance, reliable, and modularly integrated MEMS technology, many issues still need to be resolved.
- 16. Different Integration Approaches Modular integration will allow the separate development and optimization of electronics and MEMS processes. There are three main integration strategies: Pre-CMOS Post-CMOS Interleaved approach
- 17. Pre-CMOS Approach Pre-CMOS scheme was first demonstrated by Sandia National Laboratory through their IMEMS foundry process. A conventional CMOS fabrication process is performed followed by passivation of the CMOS devices. Finally, a trench is opened and the MEMS structures are released using hydrofluoric acid. The major hurdles of the “Pre-CMOS” approach include the MEMS topography. The fact that integrated circuits foundries are usually not inclined to accept pre-processed wafers.
- 18. Post-CMOS Approach Post-CMOS” scheme which was successfully demonstrated by Texas Instruments Inc. through the DMD (Digital Micro- Mirror Device), which uses an electrostatically controlled mirror to modulate light digitally, thus producing a stable high quality image on a screen.
- 19. Each mirror corresponds to a single pixel programmed by an underlying SRAM cell. Post-CMOS integration process is made possible through the usage of low temperature metal films (aluminum) as the structural layer and polymers (photoresist) as the sacrificial material.
- 20. The main hurdle when using the “Post-CMOS” integration approach is the temperature compatibility of both processes. So that a low temperature MEMS process is necessary to avoid damaging the CMOS interconnects.
- 21. The Interleaved Approach This approach has been successfully demonstrated by Analog Devices Inc. in their 50G accelerometer (ADLX 50) technology which was the first commercially proven MEMS- CMOS integrated process. The main advantage of an interleaved integration process approach is the potential better control of both the MEMS and the CMOS process. The major drawback is the often need for a compromise of the MEMS and/or CMOS steps to achieve the necessary performances.
- 22. The Analog Devices Inc. ADLX-202 of about 5mm2 holding in the middle a MEMS accelerometer around which are electronic sense and calibration circuitry.
- 24. Low Contact Resistance Si1-xGex MEMS Technology The poly-SiGeØ layer is deposited directly on top of the CMOS interlayer dielectric, through which contact openings have been formed. Any parasitic resistance will cause degradation of the signal that needs to be amplified by the CMOS circuitry and transferred through the sense-drive electrodes.
- 25. The MEMS micromachined structures are deposited directly on top of the ASIC circuitry. The interconnect resistance between the MEMS and routing metal lines needs to be low in order to minimize signal losses. In order to achieve a high performance integration technology scheme of the poly-Si1-xGex micromachined devices, the Si1- xGex films need to be heavily doped with boron to reduce the films resistivity as well as increase the films deposition rate.
- 26. Using Back-end-of-line A second approach for post-CMOS integration of MEMS with ICs is to use backend- of-line (BEOL) materials such as aluminum or copper those are already available in the integrated circuitry to fabricate the MEMS devices. The multilayered composite structural layer was made of polycrystalline silicon and aluminum metal lines. The main benefit of this technology is that “Post-CMOS” integration of MEMS on ASICs is made possible without any additional materials. A post-CMOS micromachined lateral accelerometer fabricated using aluminum based interconnects
- 27. Applications 1. Nano gap SiGe RF MEMS filter 2. RF MEMS Switches 3. Optical Add-Drop Multiplexer (OADM) 4. Ink Jet Print Heads 5. Pressure Sensor Auto and Bio applications 6. Accelerometers (Inertial Sensors – “Crash Bags”, Navigation, Safety)
- 28. CONCLUSION AND FUTURE SCOPE MEMS technology can be used to fabricate both application specific devices and the associated micro packaging system that will allow for the integration of devices or circuits, made with non compatible technologies, with a SoC environment. The monolithic integration of MEMS with CMOS remains an active research area that is crucial for the large scale production of high performance, high yield and low cost MEMS devices. The main findings of this work as well as provide future directions for the modular integration MEMS field that utilizes p+Si1-xGex and copper-based MEMS technologies.
- 29. References 1. MODULARLY INTEGRATED MEMS TECHNOLOGY By Marie-Ange Naida Eyoum www.eecs.berkeley.edu/Pubs/TechRpts/2006/EECS-2006-78.html 2. MEMS Technology by Charles Boucher, Ph.D. http://www.boucherlensch.com/bla/IMG/pdf/BLA_MEMS_Q4_010.pdf 3. Application of MEMS, http://www.seminarprojects.com/Thread-seminar-on-application-of-mems- technology 4. Qingquan Liu, Daniel T. McCormick, and Norman C. Tien, “VLSI MEMS Switches: Design, Fabrication, and Mechanical Logic Gate Application” 5. http://www-bsac.eecs.berkeley.edu/publications/search/send_publication_pdf2client.php? pubID=1161263651 6. S.Majumdar,J.lampen,R.Morrison,andJ.Maciel,MEMS SWITCHES,IEE instrumentation and measurement magazine,march 2003. 7. M. Biebl, G. T. Mulhern, and R.T. Howe, “In situ phosphorus-doped polysilicon for integrated MEMS,” 8th International Conference on Solid-State Sensors and Actuators(Transducers 95), Stockholm Sweden, Vol.1, pp.198-201, 1995. 8. R.T. Howe and T.J. King, “Low-Temperature LPCVD MEMS Technologies” Material Research Society Proceedin gs, Vol.729, No. U5.1, 2002.
Editor's Notes
- #6: 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. While Bulk micromachining creates devices by etching into a wafer, Surface Micromachining builds devices up from the wafer layer-by-layer. A typical Surface Micromachining process is a repetitive sequence of depositing thin films on a wafer, photopatterning the films, and then etching the patterns into the films.
- #15: Therefore, fabricating the MEMS devices directly on top of the CMOS metal interconnects will result in a reduction of the parasitics, that will greatly improve the system performance.
- #18: integrated circuits foundries are usually not inclined to accept pre-processed wafers because of material compatibility and contamination issues. which can compromise subsequent state-of-the art CMOS lithography steps, larger die areas due to the fact that the MEMS and CMOS devices cannot be easily stacked and the fact that that integrated circuits foundries are usually not inclined to accept pre-processed wafers.
- #25: The “SiGe0” layer is used for routing of electrical signals between the MEMS and electronics.