PiezoMEMS Workshop Aachen_180510 Oerlikon

Oerlikon PVD production solutions for piezoelectric materials

Workshop PiezoMEMSAachen,18. /19.05.2010

M. KratzerOerlikon Systems R&D

Oerlikon Systems, 17.05.2010, M. Kratzer, R&D, e-mail: [email protected]

Oerlikon company and products


Thin films used for SAW, BAW, MEMS, etc.

Dielectric Thin FilmsAlN, ZnO, SiO2,Ta2O5, TiO2,(PZT) ...

SMR Acoustic Reflectors, Temperature Compensation Layer for SAW or BAW, Ultra-thin Passivation for SAW, Passivation, RF-MEMS switches, SMR & FBAR Shunting &Trimming Layers, embedded passivesinkjet printing...

Metal Thin FilmsAl, AlCu, AlSi,W, Ti, Pt, Mo, Ir,

...

SMR Acoustic Reflectors, Bottom and Top SMR & FBAR electrodes, SAW Electrodes, MEMS Metallizations, ...

p-AlN, p-ZnO, p-PZTPiezoelectric Thin Films

Solidly Mounted Resonator, Film Bulk Acoustic Resonator, Thin Film Surface Acoustic Wave, p-MEMS sensing and actuating, RF-MEMS, bio-sensing, etc...

Resistor filmsTiW-N, TaAl-NIntegrated Resistors, Heater Elements (ink-jet)


AlN application - Bulk Acoustic Wave Filter

Figure of merit (FOM) of BAW resonator

Excellent thickness uniformity Excellent AlN texture and c-axis orientation Low stress of single film and film stack Smooth film surfaces to avoid acoustic scattering Precise temperature control during deposition Low oxygen incorporation (high base vacuum,

low leak rate)

Requirements for high AlN electro-mechanical coupling and quality factor

FOM = kt2*Q

AlN film quality

At mechanical resonance:dAlN = l /2fR = v / l = v / 2dAlN

for fR = 2.1GHz and v = 11300m/s=> dAlN ~ 2mm


n Vacuum performancen Design of gas inletn Magnetron designn Heater designn RF bias capabilityn Flexible sputter configurations (Formats, TS)n Advanced features (e.g. Flexicat)

Oerlikon production solution for AlN

n Deposition temperaturen DC powern RF biasn N2 and Ar flowsn Target-to-substrate distancen Pulse frequencyn Pulse duty cycle

n Thickness uniformityn Film stressn Texture / c-axis orientationn Surface roughness

Film properties

Process parameter

AlN deposited by DC pulsed reactive PVD process High quality of film achieved with advanced features of sputter equipment

=> High throughput and yield with constant quality

Sputter equipment


Radialcontribution

Thickness uniformity

Flexible solution neededn Target erosion over life timen Process settings (e.g. gas pressure)n Sputter geometry (TS)

Analytical decomposition into

Tiltcontribution

Measured thicknessnon-uniformity

nTarget homogeneityn Pumping geometryn Design of gas inletn Mechanics

Oerlikon FlexiCat

n Synchronized power modulationwith magnet rotation

n Movable positions of inner magnets


Target Erosion compensation with FlexiCat

FlexiCat optimisation

950.0

960.0

970.0

980.0

990.0

1000.0

1010.0

1020.0

1030.0

1040.0

1050.0

-75 -65 -55 -45 -35 -25 -15 -5 5 15 25 35 45 55 65 75

Wafer diameter [mm]

Thic

knes

s [n

m]

Pos 9

Pos 6

Pos 3

Pos 6.2

Thickness uniformity increases over target life with fixed magnetic system effect of target erosion

Effect can be compensated by FlexiCat radial adjustment of inner magnets

410

420

430

440

450

460

470

480

-75 -45 -15 15 45 75

Wafer diameter [mm]

AlN

Film

Thi

ckne

ss [n

m] new target

1/4 target life

1/2 target life

end of target life

min/max: 0.33%

min/max: 0.22%

min/max: 0.70%

min/max: 2.05%

Example for radial compensation

Thickness uniformity over target life

Movable position of inner magnets


Tilt compensation with FlexiCat

Calculation of compensation parameters from thickness measurement at 3 different settings

Control of magnet position and power synchronization with CL200 recipe software


Stress Distribution / RF Bias Power

-400

-300

-200

-100

0

100

200

300

400

0 50 100 150

Radius (mm)

Stre

ss (M

pa)

40 W

40 W

60 W

60 W

20 W

20 W

40 W

40 W

Applying RF bias to substrate lead to adjustable negative bias voltage Adjustable flux of ions with variable energy Deposition rate, thickness uniformity remains unchanged by RF Bias adjustment

Stress control through substrate RF bias

60 W

40 W

20 WTensile

Compressive


20 30 40 50 60 70 80 90 1001

Si 40

0

Si 20

0

AlN

004

AlN

002

inten

sity (

coun

ts/s)

2 Theta

A1761BAW814B-14th2th-scanMRD Cu-Ka

Crystal orientation (c-axis)

10 15 20 25 300

5000

10000

15000

20000

25000

30000

35000

40000

45000Model: GaussEquation: y=y0 + (A/(w*sqrt(PI/2)))*exp(-2*((x-xc)/w)^2) Chi^2/DoF = 29686264.57363R^2 = 0.99662 y0 1993.46717 592.85177xc 17.97655 0.00465w 1.16882 0.00958A 623291.46 4673.78FWHM 1.38 0.01

rocking curveA1761BAW814B-14AlN 00022Th=36.04

inte

nsity

(cou

nts/

s)

omega

Result for wafer BAW814-14Pure AlN 002 on q-2q1.38 AlN 002 rocking curve FWHM

Electrode surface microstructure and roughness key to high c-axis textured AlN Optimization of highly textured Mo(110), Al(111), W(110), Pt(111) and Ti(002) Ti or AlN seed layer beneficial for improving electrode texture and smoothness

q-2q scan AlN on Si substrateRocking curve - AlN (002)

Si (2

00)

AlN

(002

)

Si (4

00)

AlN

(004

)


Piezoelectric performance

d33,f [pm/V] XRD RCAlN 002

Wafer #1 (sw01)Institute A 5.2 0.2 (s)Institute B 5.8 0.5 () 1.32

Wafer #2 (sw08)Institute A 5.2 0.6 (s)Institute B 5.2 0.5 () 1.23

d33,f on Mo electrodes > 5.10 pm/V @ 2mm AlN film thickness d33,f results comparable to best values published for AlN on Pt electrodes (*) showing

the very high quality of the AlN films Electro-mechanical coupling coefficient BAW: k2>6.2%

Inverse Piezoelectric Coefficient d33,f of 2mm AlN Measured by Double Beam Interferometry at external institutes

(*) Is there a better material for thin film BAW applications than AlN?, P. Muralt et al., IEEE Ultrason. Symp. 2005


Sputtered PZT - Potential Applications Map

Comparison AlN - ZnO - PZT

main driver for growing interest in perovskitetextured PZT films


In-situ sputtering from single target- Higher quality possible compared to post anneal process- Wafer temperatures > 550C needed during deposition- RF sputtering from ceramic target- Oerlikon approach since 2008

Sputter process with post anneal step- Additional process step compared to in-situ growth- Danger of inhomogeneous phase transformation during RTP with the risk of pore

formation and irregular grain shape- Oerlikon: PZT deposition followed by RTP process at customer (2003)

Chemical Solution Deposition (CSD)- Competing technology, similar to photo resist application

Competing Deposition Methods for PZT


0.930.80100500.01599526.519.0

Composition Zr/Ti

Uniformity [%]

Thickness []tan k

Ec(kV/cm)

Pr(C/cm2)

Piezoelectriccoefficient d33,f

[pm/V]> 60

Achieved film properties

1. Strong (111) perovskite texture

2. Remanent polarization ~ 28 C/cm2

3. Coercive Field ~ 80 kV/cm

4. Typical rel. dielectric constant ~1000

5. Deposition rate: 2.5A/Sec

The below table illustrates a set of values from a similar PZT film with a different process

Ferroelectric / Dielectric Data for PZT with 450C Process & Post Anneal

Guideline for development of the in situ process :


Hardware Development for PZT sputtering

Wafer temperatures in a range of 600 - 650C achieved with a chuck temperature setpoint of 800C

Excellent temperature uniformity Chuck is capable for wafer sizes

up to 200mm

Very high temperature chuck for in-situ growth of PZT

Wafer temperature - SenseArray measurement (8" chuck)

550

555

560

565

570

575

580

585

590

595

600

-100 -80 -60 -40 -20 0 20 40 60 80 100

Radius [mm]

Tem

pera

ture

[C

]x- axisy-axisMean = 581C

Uniformity (3s) = 2.75%


Enlarged process window with stacked anode concept

Large range for sputtering process 2 10 mtorr

Adjustment of substrate / chuck bias with passive and / or active components

To avoid stray protection of materials with low melting point (e.g. Pb) in chamber additional shielding is used

RF-Source

optional

Hardware Development for PZT sputteringRF sputtering


Variation substrate bias / target voltage by RF Bias capacitor settings (substrate tuning)

=> Radial uniformity changed

Radial uniformity vs. chuck bias voltage

Uniformity PZT vs. DC Bias voltage(MB300 HA, 3kW, 20sccm Ar only, Std. anode stack, TS80, ISIT P6)

0.90

0.92

0.94

0.96

0.98

1.00

1.02

1.04

1.06

1.08

1.10

-75 -50 -25 0 25 50 75radius [mm]

norm

aliz

ed th

ickn

ess

(Y-a

xis)

DC Bias +20V (PZT_001)

DC Bias -68V (PZT_013)DC Bias -65V (PZT_014)

DC Bias +81V (PZT_015)

Dirk Kaden, Michael Kern Fraunhofer Institut ISIT April 2009

Bias and Target voltage vs. RF Bias capacitor settings

-40

-20

0

20

40

60

80

100

120

0 100 200 300 400 500 600 700 800 900 1000

RF Bias series capacitor (steps)

DC

Bia

s vo

ltage

[V]

-40

-20

0

20

40

60

80

100

120

Targ

et D

C vo

ltage

[V]

Bias Voltage - Bias Shunt Cap 900Bias Voltage - Bias Shunt Cap 100Target Voltage - Bias Shunt Cap 900Target Voltage - Bias Shunt Cap 100


In situ growth of PZT

Compositional analysis (EDX) of in-situ sputtered PZT films at different power settings

Process Result

Dirk Kaden, Michael Kern Fraunhofer Institut ISIT / Oct. 2009

RF sputter power


Target Composition Pb1.22(Zr0.52Ti0.48)O1.22 / Growth Temperature 550C

The XRD shows almost 100% of (100) oriented perovskite Phase

Scott Harada, Paul Muralt, EPFL April 2010 The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2010-2013) under grant agreement n 229196

In situ growth of PZTProcess Result


Thank you

PiezoMEMS Workshop Aachen_180510 Oerlikon

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