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EE147 / EE247AIntroduction to MEMS

OverviewProf. Ming C. Wu

wu@eecs.berkeley.edu

511 Sutardja Dai Hall (SDH)

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MEMS Inertia Sensors

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ADXL Sensors

https://www.analog.com/en/technical-articles/mems-accelerometers-for-condition-monitoring.html

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ADI’s ADXL Family of Accelerometers

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Sensors in Smartphones

Lots of sensors:

• 9 DoF motion sensing, – 3 axis accelerometer– 3 axis gyroscope– 3 axis compass

• 3 microphones,

• multiple image sensors,

• ambient light

• proximity sensors,

• touch screen sensor

• finger print sensor

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Inside iPhone4

www.memsjournal.com/2010/12/motion-sensing-in-the-iphone-4-mems-accelerometer.html

Accelerometer

Gyroscope

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Accelerometer in iPhone4

www.memsjournal.com/2010/12/motion-sensing-in-the-iphone-4-mems-accelerometer.html

• Made by STMicroelectronics• ASIC stacked on MEMS• Wafer level packaging (WLP)

for MEMS

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Accelerometer in iPhone4

www.memsjournal.com/2010/12/motion-sensing-in-the-iphone-4-mems-accelerometer.html

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Ubiquitous Sensors

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Face ID Sensor

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Dot Projector

https://www.techinsights.com/blog/apple-iphone-x-teardown

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Dot Projector

https://www.barrons.com/articles/ams-ag-is-biggest-winner-in-apples-3-d-sensing-says-bernstein-1523384069

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Inertial Measurement Unit (IMU)Bosch’s 6-Axis IMU

6 mm thick

https://www.systemplus.fr/wp-content/uploads/2018/01/SP18382-Bosch-IMU-in-iPhone-X_flyer.pdf

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Wearable Sensors

• GPS

• Barometric altimeter

• Electrical heart sensor (ECG app)

• Optical heart sensor

• Accelerometerup to 32 g-forces

• Gyroscope

• Ambient light sensor

Apple

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ECG / SpO2

• Two commonly used devices to monitor patient health are Electrocardiogram (ECG) and Blood Oximetry (SpO2) sensors

• ECG uses a bunch of op-amps to amplify a weak signal that can be used to diagnose the health of the heart

• SpO2 uses light / infrared diodes and photosensors + interface electronics to measure blood oxygen levels

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Medical Electronics

• Inside every medical device, you will find a range of sensors and interface electronics

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Prof. Ali Javey Lab

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Brain-Machine Interfaces

Hochberg, Nature ‘12 Source: Hochberg et al., Nature ‘12

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Automotive Sensors

https://www.fierceelectronics.com/components/automotive-sensors-driving-to-a-smooth-6-71-cagr

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Self-Driving Car without Drivers

• California approves testing of self-driving cars without human backup drivers

Multiple LiDARs

Waymo

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Micro-Electro-Mechanical Systems (MEMS)

• A way of making things– Leverage on existing infrastructure of IC fabrication tools– Prototype on mass-production fabrication tools

• Co-location of sense, compute, actuate, control, communicate, power

– Increase performance and decrease cost– Integrate an increased number of fabrication technologies

• Closed-loop, microscale control of electrical, thermal, fluid, magnetic, optical, and mass flux

– Control phenomena on the microscale– Cause large effects both on macroscale and microscale

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Invention of Transistors - 1947

• Bardeen, Shockley, and Brattain at Bell Labs

• Invented bipolar transistor in 1947• Nobel prize in 1956• Shockley sometimes credited as “the

man who brought silicon to Silicon Valley”

Point contact bipolar transistor(Ge)

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First MEMS Device: Resonant Gate

Transistor (Westinghouse) - 1965

S D

Gate

Si

H. C. Nathanson and R. A. Wickstrom, “A Resonant-Gate Silicon Surface Transistor with High-Q

Band-Pass Properties,” Applied Physics Letters, vol. 7, no. 4, pp. 84–86, Aug. 1965.

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Clocks with MEMS Oscillators

First MEMS clock company: Discera, Prof. Clark Nguyen

SiTime- Prof. Bernhard Boser

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First Optical MEMS Device –Mirror-Matrix Tube (Westinghouse) 1975

Al2O3

R. N. Thomas, J. Guldberg, H. C. Nathanson, and P. R. Malmberg, “The mirror-matrix tube: A novel light valve for projection displays,” IEEE Transactions on Electron Devices, vol. 22, no. 9, pp. 765–775, Sep. 1975.

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Texas Instruments Digital Micromirror Devices (DMD)

~ 1 million DMD’s on a chiphttp://www.dlp.com/dlp/resources/dmmd.asp

“25 Microchips That Shook the World” IEEE Spectrum, May 2009

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MEMS Size Effect

Ants can carry 100x their body weights

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• Silicon is being increasingly employed in a variety of new commercial products not because of its well-established electronic properties, but rather because of its excellent mechanical properties

• Examples mentioned: – Inkjet print head– Gas chromatograph– Pressure sensors– Si torsional mirrors– Projection display– Accelerometers– MEMS switch / relay

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Technology Evolution

Berkeley Sensor and Actuator Center (BSAC) founded in 1986

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