This document presents information on MEMS (Micro-Electro-Mechanical Systems) technology. It discusses what MEMS are, how they compare to integrated circuits, market opportunities for MEMS, approaches to integrating MEMS with electronics, and applications of MEMS technologies. Key integration approaches discussed are pre-CMOS, post-CMOS, and interleaved approaches. The document also provides a conclusion on the future scope of MEMS technology and modular integration with references.

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.

23. Schematic Description

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.