MEMS: Basic structures

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MEMS Basic structures Current Applications

• Presented by
• Amit Kumar Sharma
• Amit Bansal
• Amit Goyal

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What are MEMs?

• Micro Electro Mechanical Systems/Sensors.
• Machines fabricated at micro scale .
• The basic principles being that of Electrical and
  Mechanical machines.
• In the simplest terms miniaturization of
  electro-mechanical devices by application of
  semiconductor fabrication techniques.

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MEMs

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Microengine(Comb Drive Actuator)

• How they work
• The light brown fingers are fixed to the
  substrate, and the black fingers are free to
  move. 
• By applying a voltage alternately to the top and
  bottom brown fingers, the electrostatic force
  causes the black structure to start to resonate. 
  
• A mass attached to the comb drive resonator can
  be made to translate

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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microengine(Comb Drive Actuator)
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Microtransmission(Gears and Shaft)

• To increase the torque available from a rotary
  drive, a multi-layer microtransmission was
  developed.
• Output gear of a microengine, may be meshed with
  a linear rack to provide linear motion with a
  high degree of force.

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Microtransmission(Gears and Shaft) contd.

• The transmission, shown, employs sets of small
  and large gears that mesh with each other to
  transfer power while providing torque
  multiplication and speed reduction .

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Micromirror(Digital Micromirror Devices )

• DMD's are large matrix (640 by 480 and higher) of
  tiny mirrors (16µm square mirrors with 1µm
  spacing between mirrors).
• DMDs are used in smaller, lighter display
  devices having better resolutions.

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Micromirror(Digital Micromirror Devices )

• On a DMD consists of three physical layers and
  two "airgap" layers. The airgap layers separate
  the three physical layers and allow the mirror to
  tilt 10 or -10 degrees.
• When a voltage is applied to either of the
  address electrodes, the mirrors can tilt 10
  degrees or -10 degrees, representing "on" or
  "off" in a digital signal.

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APPLICATIONS
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Three-axis accelerometer

• inertial sensors, examples of which are Analog
  Devices ADXL1508 and Motorola's XMMAS40GWB9. The
  primary application of these accelerometers is as
  airbag-deployment sensors in automobiles, but
  they are also being used as tilt or shock sensors
  
• The application of these types of accelerometers
  as inertial measurement units is limited by the
  need to manually align and assemble them into
  three-axis systems, the resulting alignment
  tolerances, their lack of on-chip A/D conversion
  circuitry, and their lower limit of sensitivity.

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Three-axis accelerometer contd.

• For inertial measurement
• units (three-axis
• acceleration and three-axis
• rotation rate) were built
• using Sandias Integrated
• MicroElectroMechanical
• Systems (IMEMS) Technology.
• This system-on-a-chip is a
• realization of a full three-
• axis inertial measurement
• unit that does not require
• manual assembly and
• alignment of sense axes.

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Projection TV

• Home theater system
• Screen size greater than 40 inches (101 cm)
  

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Projection TV

• In a projector, light shines on the DMD. Light
  hitting the "on" mirror will reflect through the
  projection lens to the screen. Light hitting the
  "off" mirror will reflect to a light absorber.
  Each mirror is individually controlled and is
  totally independent of all the other mirrors.

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The Future of Projection TV virtual reality
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Microactuator

• Microactuator for HDD is developed to satisfy the
  growing needs for higher track density and higher
  performance of the future generation drives

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Microactuator

• a micro-actuator attached between the slider and
  the suspension beam in order to move the slider
  with high speed and high accuracy.

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Microactuator

• To achieve relative motion between the head and
  suspension, the device pictured below positions
  the rotor with tiny springs and generates forces
  between rotor and stator using electrostatic
  attraction.

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Micromechanical Switches

• Low contact resistance.
• Low threshold voltage.
• High switching speed

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Micromechanical Switches

• When a voltage is applied to the gate electrode,
  the beam is pulled down by electrostatic force
  until the switch closes.
• When the gate voltage is removed, the restoring
  force on the beam returns it to its original
  position.

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Micromechanical Switches

• SEM micrograph of a completed three terminal
  switch.
• Low contact resistance.
• Low threshold voltage.
• High switching speed

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Conclusion

• A technology involving micromachined devices
  embedded below the surface of a wafer, prior to
  fabrication of microelectronic devices, was
  developed and applied to build complex sensor
  systems on a single chip. A three-layer
  polysilicon process made possible intricate
  coupling mechanisms that link linear comb-drive
  actuators to multiple rotating gears. This
  technology has been used to build devices such as
  microengines, microtransmissions, and
  micromirrors. These devices were also combined to
  yield intricate mechanical systems-on-a-chip.

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Conclusion

• The predominant technology at present state is
  surface micromachining, and current developments
  show that this trend will continue in the future.
• The other industries such as space, aeronautical,
  and automotive will continues to substitute the
  conventional sensors with the MEMS equivalents.
• The designer of electromechanical systems should
  pay attention to the availability of sensors and
  devices on the market.
• When possible, the choice have to fall on MEMS
  devices, as these are commonly cheaper, more
  accurate and reliable, and less cumbersome.