IntroductIon / MotIvatIon

ExpErIMEntal

rEsults

conclusIon

1 ) F r a u n h o F e r I n s t I t u t e F o r e l e c t r o n B e a m a n d P l a s m a t e c h n o l o g y F e P, W I n t e r B e r g s t r a s s e 2 8 , d r e s d e n , g e r m a n y

D. GloeSS1), S. Barth1), h. BartzSch1), P. Frach1), t. herzoG2), S. Walter2), h. heuer2), G. Suchaneck3), G. Gerlach3), J. Juuti4), J. PaloSaari4)

sputtEr dEposItIon of pIEzoElEctrIc aln and alscn fIlMs for ultrasonIc and EnErgy harvEstIng applIcatIons

aln - a proMIsIng MatErIal for thIn fIlM pIEzoElEctrIc dEvIcEsAluminum-Nitride thin films are known and used since 1990s, mostly for resonator devices like SAW filters

• c-axis orientation necessary for thickness vibration• low temperature deposition process possible• can be combined with conventional semiconductor manufacturing processes• high temperature stability

Potential applications:• ultrasonic wave devices• SAW and BAW devices• energy harvesting• LED‘s

charactErIstIcs of pulsE MagnEtron sputtEr procEss

• excellent process stability and reproducibility

• stoichiometric compound layers (e.g. AlN, SiO2, Al2O3, TiO2) with very low absorp-tion and high barrier properties (electrical insulation, diffusion barrier)

• deposition of dense climatically stable films by intense energetic substrate bom-bardment during deposition

• very high deposition rates (e.g. AlN: 3 nm / sec)

• uniform coating of large substrates

• efficient methods of substrate pre-treatment by plasma processes to ensure good layer adhesion

eu and the state of saxony (grant-in-aid for technology Funding by the european regional development Fund 2000-2006)

acknowlEdgEMEntscorrEspondIng contactF r a u n h o f e r - I n s t i t u t f ü r e l e k t r o n e n - s t r a h l - u n d P l a s m a t e c h n i k F e P

W i n t e r b e r g s t r a ß e 2 80 1 2 7 7 d r e s d e n , g e r m a n y

w w w. f e p . f r a u n h o f e r. d e

d r. d a n i e l g l ö ßd a n i e l . g l o e s s @ f e p . f r a u n h o f e r. d e

P h o n e : + 4 9 - 3 5 1 - 2 5 8 6 - 3 9 4F a x : + 4 9 - 3 5 1 - 2 5 8 6 - 5 5 - 3 9 4

2 ) F r a u n h o F e r I n s t I t u t e F o r n o n d e s t r u c t I v e t e s t I n g d r e s d e n B r a n c h I Z F P - d , m a r I a - r e I c h e - s t r a s s e 2 , 0 1 1 0 9 d r e s d e n , g e r m a n y

hardwarE and tEchnology for aln dEposItIon - doublE rIng MagnEtron drM 400

4 ) u n I v e r s I t y o F o u l u l I n n a n m a a , m I c r o e l e c t r o n I c s a n d m at e r I a l P h y s I c s l a B o r at o r I e s , 9 0 0 1 4 o u l u , F I n l a n d

3 ) t e c h n I s c h e u n I v e r s I t ät d r e s d e n , s o l I d - s t at e e l e c t r o n I c s l a B o r at o r y, 0 1 0 6 2 d r e s d e n , g e r m a n y

• reactive pulse magnetron sputtering (PMS) from metallic Al target• deposition rate: 3 nm / s• substrate size: Ø 200 mm• film thickness uniformity: up to ±0.5%• layer thickness: up to 50 µm

pulsE Echo MEasurEMEnts as dEMonstratIon for us sEnsors

EnErgy harvEstIng

Double ring magnetron (DRM 400)

for uniform coating of Ø 200 mm (8”)

substrates.Superposition of film thickness distributions of two concentric discharges.

Power output vs. frequency (80 kΩ load, 2.5 µm base displacement)

Average power output vs. displacement(at optimal resistive load and resonance frequency)

Measurement principles: • berlincourt piezometer PM 300 (piezotest)

for piezoelectric charge constant (d33)• pulser / receiver setup (DPR500, JSR

Ultrasonics) with PC digitizer card for pulse echo measurements

• samples were put into mechanical base and vibrated by a shaker as a function of frequency• constant excitation of approx. 5 μm peak-to-peak displacement for mechanical base was

maintained for each frequency • displacement of the tip of the samples was recorded at the resonance frequency

by vibrometer measurement• generated power was measured as a function of resistive load,

measurement by multimeter connected in parallel to the load• maximal generated power in resonance and using optimal load

• deposition of AlN films by reactive pulse sputtering at high deposition rate was successful

• piezoelectric coefficient on unheated substrates: AlN: d33=7.2 pm / V AlXSc1-XN: d 33=29 pm / V

• application e.g. in SAW, BAW, LED, ultrasonic transducers, energy harvesting, ...• AlN shows lower d33 than PZT - However, it is well suited for energy harvesting

applications, because of it‘s high acoustic velocity and relatively high d31

• measurements of energy harvesting properties of AlXSc1-XN are under progress

d33=0.6 pm / V

AlN: not optimized condition with irregular orientation

AlN: optimized conditions Sc doped layers (AlXSc1-XN)

d33=7.2 pm / V d33=29 pm / V

scandIuM-dopIng (alxsc1-xn)

• reactive Co-Sputtering from

metallic Al- und Sc-Targets

• deposition rate: 2 nm / s

• improvement of d33 up to

30 pC / N

• signal level of pulse-

echo-measurement of AlX-

Sc1-XN in comparison to AlN

show same increase as d33

EnErgy harvEstIng propErtIEs of aln layErs• size of energy harvesters: 8 × 80 mm (substrate thickness: 0.57 mm; layer thickness: 10 ... 50 µm)

• 1st / 2nd resonance frequency was observed at approx. 150 Hz / 700 Hz

• best samples showed average (RMS) power of 141 µW at optimal resistive load and 5 µm base

displacement

bipolar

t [ns]

max

. sig

nal v

olta

ge [V

](36d

Bgai

n)

unipolarnot optimized

time in ns [200ns / Div]

Ø 10 mm

Ø 13 mm

100 nm Al

10 µm AlN

500 µm Si

Frequency [Hz]

Sc concentration [%] puls

e ec

ho V

Pk-P

k [m

V]

d 33[p

C / N

]

Displacement [µm]

Inte

nsity

in c

ps

Inte

nsity

in c

ps

Inte

nsity

in a

. u.

2 Theta in deg 2 Theta in deg2 Theta in deg

Pow

er [u

W]

Pow

er [u

W]

sign

al v

olta

ge in

V

double ring magnetron (DRM)

outer discharge

inner discharge

radial position on the substrate [mm]

rela

tive

film

thi

ckne

ss [%

]

Excitation pulse followed by multiple reflections from the silicon backside.

august 2013 – energy harvesting: a metrological approach

poster online (pdf) corresponding contact