This presentation discusses piezoelectric MEMS actuators using thin film piezoelectric materials. It begins with an introduction to piezoelectricity and discusses lead zirconate titanate (PZT) as the most commonly used piezoelectric material. The presentation then covers the processing of thin film PZT, including sol-gel deposition and patterning techniques. Several applications of piezoelectric MEMS actuators are presented, including inkjet printheads, autofocus camera lenses, micropumps, and ultrasonic transducers. The presentation concludes by discussing opportunities for piezoelectric energy harvesting and ST's role in commercializing thin film piezo MEMS technology.

1. October 4, 2016
Santa Clara Convention Center
Mission City Ballroom
MEMS Piezo Actuators
Simon Dodd

2. Agenda
16:20 MEMS in ST Simon Dodd
What is Piezo?
17:00 Thinfilm Piezo Processing
Applications
Conclusion
Time
Speaker
Presentation
2

3. MEMS Piezo Actuators
A piezo-electric material, such as PZT (Lead Zirconium Titinate),
is a substance that links mechanical movement to electrical
potential. If voltage is applied to the PZT, a mechanical
deflection is observed. Or, if a deflection is induced in the PZT, a
voltage is generated. Thick piezo actuators (1mm) have been
around for 30+ years, but deposited PZT material (2um) is just in
its commercial infancy. This thinfilm piezo capability can be
implemented in high volume production already in use for
MEMS sensors. The development of the technology has led to
the creation of custom piezo print heads and a revolutionary
autofocus lens. This presentation will give an introduction to the
technology and show potential uses in other market segments.
3

4. Sensing and Actuating
Complementary Phenomena
Feel Move
See Project
Hear Make sound
4

5. Sensing and Actuating
MEMS act in both directions
Sensors
Micro-actuators
MEMS
Signal
Electric
Motion
Piezo actuators
Physical
change
Mechanical
Fluidic
Micro-actuators
Environmental Audio
Electro
Mechanical
Micro
Mirrors
5

6. Building Micro-actuators
Micro-mechanical
part
Micro-mechanical
part
Analog signal
processing
Analog signal &
power management
Sensors
Micro-actuators
MEMS micro-actuators have high
voltage/current analog and power
management parts
(since higher voltages required for some
applications)
MEMS sensors have ultra-low
power analog signal processing
parts
MEMS micro-actuators & MEMS sensors use the same principles and same basic
processes
Leveraging ST BCD technologies
6

7. What is ‘Piezo’?

8. What is a piezoelectric element?
Piezo
Element
Voltage Meter
or
Voltage SourceThe piezo element
generates a voltage
when deformed
If a voltage is applied
across the piezo
element, it will deform
Source: https://en.Wikipedia.org/wiki/Energy_harvesting
8

9. History
First demonstration of a
piezoelectric material was by
Pierre and Jacques Curie – 1880.
First use was a Quartz
based sonar
9

10. Piezo Materials
• Aluminium nitride
• Apatite
• Barium titanate
• Bimorph
• Bismuth titanate
• Gallium phosphate
• Lanthanum gallium silicate
• Lead scandium tantalate
• Lead zirconate titanate
• Lithium tantalate
• Polyvinylidene fluoride
• Potassium sodium tartrate
• Quartz
• Sodium bismuth titanate
• Unimorph
• Zinc Oxide
Aluminum nitride (AlN)
Lead zirconate titanate (PZT)
10

11. What is PZT?
Solid solution: Pb(Zrx,Ti1-x)O3 – Perovskyte structure
PZT has the best ferroelectric and piezoelectric performances at
morphotrophic phase boundary (MPB), where rhomboedral and
tetragonal phase are coexisting.
This happens for Zr/Ti ~ 52/48
P along <100>
Zr/Ti
Pb
O
P along <111>
Pure PbTiO3
Tetragonal
Pure PbZrO3
Rhomboedral
Pb
O
Zr/Ti
11

12. The word piezoelectricity means literally “electricity resulting from pressure”
Actuation conditions:
• Triangular wave form actuation
(20V peak);
• Frequency ~1Hz;
 30um displacement
PZT
cantilever
A A
Fabricated and characterized in ST
Cantilever actuated with PZT Technology 12

13. Bulk Piezo Thin Film Piezo
• Large form factor
• High power
consumption
• Mechanical assembly
requires high capital or
low volume
manufacturing
• Micron thick layers
produce 2D form
factor
• Lower drive voltages
for similar mechanical
displacement
• Integrated into fab
processing for very
high volume
manufacturing
Advantages of Thin Film Piezo
vs Bulk Piezo
13

14. Thinfilm Piezo Processing

15. MEMS Processing
• Material Substrate
• Silicon
• Flexible
• Biocompatible material (polyamide)
• Dry and Wet etching
• Permanent and Photosensible: from 1 to 20 um
• Physical Vapor Deposition: e-beam, sputtering
• Chemical Vapor Deposition
• Electroplating: Au up to 20um
• Full range of Metals
• Ag, Au, Al, Ir, Cr, CrSi, Cu, Fe, Ni, Pd, Pt, Co
• Full range of dielectric materials
• SiNx, SiOx, SiON
• One & Double side Lithography
• Dry and Wet Etch
• Wafer/Wafer Bonding
Process Modules & Materials
MEMS technology can be used to
produce geometrically well defined,
highly reproducible structures and
surfaces area
Technologies
15

16. Sol Gel PZT
Cristallisation
RTA
Spinning Drying
Hot plate 1
Calcination
Hot plate 2
3 times
ntimes(tofinalthickness)
2 um PZT
16

17. PZT Film Quality
2 um PZT
Bottom electrode
Top electrode
SEM
TEM
• Very dense film structure, columnar grains
• No defects/voids visible in the film or at interfaces between coatings
• Film is flat with very small grain
17

18. • The 2um thick etched PZT and Electrodes
• Sloped sidewalls for good passivation step coverage
Cross section SEM view Tilted SEM view
Top Electrode
Bottom Electrode
PZT
PZT
Top Electrode
Bottom Electrode
Oxide
PZT Definition 18

19. Sputter PZT
Sources: www.ulvac.co.jp, www.Fujifilm.com/about/research/
Advantages:
• Can be done at 500C
• Can integrate higher
percentage of Nb
Disadvantages:
• Infantile technology
• Only one company with
real experience
19

20. Thin Film Piezo Applications

21. Source: Yole Development
21

22. Printhead using PZT
• Working principle: ink volume displacement by a PZT actuated membrane
• Thin-Film Piezo vs Thermal Inkjet Benefits
• Compatibility with wide set of inks (hot melt or wax based fluids)
• Higher printing speed > 80KHz
• Superior print output quality
• Extended print-head lifetime
22

23. Microfluidic channels realized by processing multiple wafers
Nozzle wfs
PZT wfs
Inlet wfs
Cavity
Nozzle
Squish
Nozzle
Chamber
Inlet
Inlet
channel
Inlet
channel
Inlet
PZT
ink inkinkinkinkinkink ink
ink
PZT
Si
Si
Si
Printhead Cross Section
PZT actuator
Ink
Cavity
Actuator
Cavity
23

24. 24

25. Fluid = 70%H2O+30%Glycol
Pull Push mode, 30Volt
PW=4us
Fire freq=5kHz
Drop Weighht= 5pl
Velocity= 8m/s
Printhead Test Vehicle 25

26. 20 Actuators
10kHz/ Actuator
2 seconds firing
=
400,000 drops
26

27. Norway’s poLight® using
the ST Piezo technology
to revolutionize mobile-
camera autofocus function
The ST Piezo deforms the
membrane when a voltage is
applied, while a soft polymer
acts as a deformable lens
providing variable focus
Preparing for market
launch in H1 2017
Courtesy of poLight TLens
poLight T-Lens® for Auto Focus Camera 27

28. Source: www.poLight.com
Response time: <1 mS
Power consumption: < 5 mW
Field of view: No AF pumping
Smallest Footprint: 3.2 x 3.2 mm2
Product performances
Glass membrane
PZT Piezo film
Polymer optic
Glass
Silicium
From MEMS Wafer to Camera module
Principle
of operation
Implementation
Lens made of a glass
membrane actuated
by a PZT layer
TLens® Technology – Auto Focus Actuator 28

29. Source: www.poLight.com
TLens® vs. VCM (Voice Coil Modulator) 29

30. ST’s industrial design & manufacturing process
The Heart of the Insulin Jewel PUMP® 30

31. Pump Wafer Stack 31

32. Backside panoramic (SEM)
Inlet valve (SEM)
Outlet
valve
(SEM)
Pump Valves 32

33. Ultrasonic Transducers
Source: http://www.cyberphysics.co.uk/
Typical transducer cross section used for Medical imaging
33

34. Transducer Arrays
Sources: http://www.mdpi.com/materials/ . Mdpi sensors-15-08020
Bulk Piezo:
• Each segment diced
• Mechanical Assembly
Thinfilm Piezo:
• 200um transducers
• Patterned at wafer level
• Any shape, any quantity
• Integrate into or near ASIC
34

35. MEMS Actuation Technologies
Piezoelectric Actuators
Electrostatic Mirrors
Electromagnetic Mirrors
MEMS
And
BCD Drivers
35

36. Optical Micro-actuators for Projection 36
HUD
Drivers Information
HMD
Wearable Devices
Image Projection
Extending Mobile Displays

37. Intel RealSense® Depth Camera
http://www.intel.com/content/www/us/en/architecture-and-technology/realsense-overview.html
MEMS
µMirror
Powers
IR Projector
(Some) Applications Examples
3D Scanning for 3D Printing,
Accurate Gesture Control for Immersive Gaming
Face Recognition
Object Avoidance in autonomous devices
37

38. Energy Harvesting
Sources: http://www.npl.co.uk/science-technology/functional-materials/research/vibrational-energy-harvesting , SPIE
Massmovement
oncantilever
Magneticfield
movementon
cantilever
Generating small
amounts of power
through piezoelectric
deformation
50nW/mm3 is best in
class for micro scale
generation
38

39. Applications for Harvesting 39
Sources: https://www.mdtmag.com/, http://assets.inhabitat.com/,
http://www.the-scientist.com/, http://www.leopard.t.u-tokyo.ac.jp/
Shoes, Pacemakers, TPMS,
Ingestible Electronics,
Remote Sensor Arrays

40. Conclusion

41. Conclusion
• A broad and untapped range of applications possible
• MEMS utilizing Thin Film Piezo provide the required large linear forces with
fast actuation at small drive voltages
• Industrial scale integration of Thin Film Piezo into MEMS is being developed
• ST is currently finalizing industrialization phase for high volume manufacturing
• Partnership with market leaders and emerging startups is key to drive the
creation of new markets
41

42. Thank You!
Piezo MEMS Actuators
Simon Dodd
Technical Marketing Director
MEMS Actuator Division
ST Microelectronics
simon.dodd@st.com