October 4, 2016

Santa Clara Convention Center

Mission City Ballroom

MEMS Piezo Actuators

Simon Dodd

Agenda

16:20 MEMS in ST Simon Dodd

What is Piezo?

17:00 Thinfilm Piezo Processing

Applications

Conclusion

Time

Speaker

Presentation

2

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

Sensing and ActuatingComplementary Phenomena

Feel Move

See Project

Hear Make sound

4

Sensing and ActuatingMEMS act in both directions

Sensors

Micro-actuators

MEMSSignal

Electric

Motion

Piezo actuators

Physical

change

Mechanical

Fluidic

Micro-actuators

Environmental Audio

Electro

Mechanical

Micro

Mirrors

5

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

What is ‘Piezo’?

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

HistoryFirst demonstration of a

piezoelectric material was by

Pierre and Jacques Curie – 1880.

First use was a Quartz

based sonar

9

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

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

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

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 Piezo13

Thinfilm Piezo Processing

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

Sol Gel PZT

Cristallisation

RTA

Spinning Drying

Hot plate 1

Calcination

Hot plate 2

3 times

n tim

es (to

final th

ickne

ss)

2 um PZT

16

PZT Film Quality

2 um PZT

Bottom electrode

Top electrode

SEMTEM

• 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

• 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

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

Thin Film Piezo Applications

Source: Yole Development

21

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

Microfluidic channels realized by processing multiple wafers

Nozzle wfs

PZT wfs

Inlet wfs

Cavity

Nozzle

Squish

No

zzle

Chamber

Inle

t

Inletchannel

Inletchannel

Inle

t

PZT

ink inkinkinkinkinkink ink

ink

PZT

Si

Si

Si

Printhead Cross Section

PZT actuator

Ink Cavity

Actuator Cavity

23

24

Fluid = 70%H2O+30%Glycol

Pull Push mode, 30Volt

PW=4us

Fire freq=5kHz

Drop Weighht= 5pl

Velocity= 8m/s

Printhead Test Vehicle 25

20 Actuators

10kHz/ Actuator

2 seconds firing

=

400,000 drops

26

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

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

ImplementationLens made of a glass

membrane actuated

by a PZT layer

TLens® Technology – Auto Focus Actuator 28

Source: www.poLight.com

TLens® vs. VCM (Voice Coil Modulator) 29

ST’s industrial design & manufacturing process

The Heart of the Insulin Jewel PUMP®30

Pump Wafer Stack 31

Backside panoramic (SEM)

Inlet valve (SEM)

Outlet

valve (SEM)

Pump Valves 32

Ultrasonic Transducers

Source: http://www.cyberphysics.co.uk/

Typical transducer cross section used for Medical imaging

33

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

MEMS Actuation Technologies

Piezoelectric Actuators

Electrostatic Mirrors

Electromagnetic Mirrors

MEMS

And

BCD Drivers

35

Optical Micro-actuators for Projection 36

HUD

Drivers Information

HMD

Wearable Devices

Image Projection

Extending Mobile Displays

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

Energy Harvesting

Sources: http://www.npl.co.uk/science-technology/functional-materials/research/vibrational-energy-harvesting , SPIE

Mass m

ovem

ent

on c

antile

ver

Magnetic f

ield

movem

ent

on

cantile

ver

Generating small

amounts of power

through piezoelectric

deformation

50nW/mm3 is best in

class for micro scale

generation

38

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

Conclusion

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

Thank You!

Piezo MEMS Actuators

Simon Dodd

Technical Marketing Director

MEMS Actuator Division

ST Microelectronics

simon.dodd@st.com