Integration of Thin-Film Galfenol with MEMS Cantilevers for Magnetic ...

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[email protected]. ETREMA Products, Inc. Neeta Basantkumar. Capacitance Bridge. Vin. Vo. C3. C4. C1. C2 .... ❖Sputter Beam Material. ❖Wet Etching. Si.
ETREMA Products, Inc.

Integration of Thin-Film Galfenol with MEMS Cantilevers for Magnetic Actuation Rajneeta R. Basantkumar, Bethanie J. H. Stadler, William P. Robbins and Eric M. Summer* Department of Electrical and Computer Engineering, University of Minnesota * ETREMA Products, Inc

Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Outline ™Motivation ™Experimental ™Fabrication of Galfenol films ™Calculation of Magnetostriction

™Galfenol Film Results ™Fabrication of Cantilever Beams ™Conclusions Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Motivation ™Study properties of Galfenol at microscale ™MEMS devices ™Sensors

From NSWC-Carderock Division courtesy M. Wun-Fogle, J.B. Restorff, A.E. Clark, et al.

- magnetic field - chemical - acoustic

™Medical (eg: opthalmology) ™Telecommunication ™Etc Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

RF-Sputtered Galfenol Films ™ Glass substrates ™ Galfenol targets (18.4%) ™ Sputtering power – 60-100W, 20W increment ™ Deposition time – 30 and 60 mins ™ Glass flow rate – 10-50 sccm, 10 sccm increment ™ Deposition rate – 2-4 nm/minute

Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Capacitance Bridge

Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Capacitance Bridge b C2

C1 a

c

Vo

C4

C3 d

Vin

C1 and C2 – Fixed capacitors C3 – Variable capacitor C4 – Sample (Unknown)

Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Calculation 1 ∆C ™ Magnetostrictive coefficient, λm = k t f C02 k = [Esε0wtf2 (1+ νf)] / (EfL)

*

Es = Young’s Modulus of Glass Substrate = 65.0 GPa Ef = Young’s Modulus of Film (Galfenol) = 72.4GPa - 86.3GPa** ε0 = Dielectric constant of insulator (air) = 8.854x10-12 F/m νf = Poisson’s ratio of film (Galfenol) = 0.3 νs = Poisson’s ratio of substrate (Glass) = 0.17 w = width of substrate (glass) = 18 mm ts = thickness of substrate (Glass) = 0.125 mm L = length of substrate (Glass) = 18 mm tf = thickness of film (Galfenol) C0 = initial capacitance before magnetic field ∆C = | Cf - C0| = capacitance difference before and after magnetic field * ε = Ef(1- ν s)/Es(1-σf) 3 t l 2

™ Deflection, d =

f

ελ m

t s2

*E. Klokholm, IEEE Trans. Magnetics. 12 819 (1976) **E. M. Summers, A.T. Snodgrass, J.D. Jonathan, J.C. Slaughter, Proc. SPIE 5387 448 (2004)

Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Outline

™Motivation ™Experimental ™Fabrication of Galfenol films ™Calculation of Magnetostriction

™Galfenol Films Results ™Fabrication of Cantilever Beams ™Conclusion Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Crystallography

[110] orientation of Galfenol thin films Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Sample Summary λm (ppm)

Deflection (µm)

30.1

35.0

0.14

75

21.4

32.3

0.19

30

133

19.4

16.3

0.17

20

60

92.4

26.6

109

0.81

80

20

60

146.5

23.8

147

1.71

100

20

60

211.7

19.5

35.6

0.25

80

30

60

130.8

23.3

60.0

0.55

100

30

60

195.2

15.2

120

1.86

Power (W)

GasFlow (sccm)

Time (mins)

tf (nm)

60

20

30

49

80

20

30

100

20

60

% Ga

Examples of experimental data showing the thickness, concentration of Ga, and magnetostriction Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Magnetic Properties 1.25

Fe 0.75

0.25 M/Ms

60W60min 20sccm -0.25

80W60min 20sccm

-0.75

100W60min 20sccm

-1.25 -50

-30

-10

10

30

50

Field (Oe)

The hysteresis loops showing the dependence of coercivity on the forward power Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Composition and Coercivity 35

2.5

%Ga for 20sccm,60 mins

25

1.5

20

15 50

60

70 80 90 Forward Power (W)

100

0.5 110

Coercivity (mT)

% Ga

30

%Ga for 20sccm,30 mins

Coercivity for 20sccm,60 mins

Atomic % Ga and coercivity dependences on the forward power Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Recall – For bulk Galfenol

From NSWC-Carderock Division courtesy M. Wun-Fogle, J.B. Restorff, A.E. Clark, et al.

Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Double Peak Trend – λs vs. %Ga 160 140

Magnetostriction (ppm)

120 100 80 60 40 20 0 0

5

10

15

20

25

30

35

%Ga

Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Outline ™Motivation ™Experimental ™Fabrication of Galfenol films ™Calculation of Magnetostriction

™Galfenol Films Results ™Fabrication of Cantilever Beams ™Conclusions Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Fabrication of Cantilever Beams ™Photolithography ™Reactive Ion Etch ™Remove PR

Galfenol

Si3N4

Si

™Sputter Beam Material ™Wet Etching Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Conclusions

™Successfully deposited Galfenol thin films [110] on glass cover slides

™Composition of films controlled by

forward power and magnetic properties controlled by the composition

™Magnetostriction up to 147 ppm ™Fabricated cantilever beams Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Acknowledgements ™Office of Naval Research (ONR) for funding through ETREMA Products, Inc., Ames, Iowa through grant number N00014-05-C-0165

™Prof. Joey Talghader for providing the cantilever masks

Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Questions?

Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Sizes vary from 180microns to 950 microns

Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]

ETREMA Products, Inc.

Neeta Basantkumar

www.ece.umn.edu/users/stadler [email protected]