Development of Coplanar Waveguides on Cyclic-Olefin Copolymer for Terahertz Applications

L. M. Diaz-Albarran1,2, E. Lugo-Hernandez1,2, E. Ramirez-Garcia2,

M. A. Enciso-Aguilar2, D. Granados3, P. Cereceda1, and J. L. Costa-Krämer1,*

1 IMM Instituto de Microelectrónica de Madrid (CNM-CSIC), Issac Newton 8, PTM, E-28760 Tres Cantos, Madrid, Spain

2 Instituto Politécnico Nacional, UPALM, Edif. Z-4 3er Piso, CP 07738, México D.F, México.

3 IMDEA Nanociencia, Campus Cantoblanco, Calle Faraday, 9, 28049 Madrid

*kramer@imm.cnm.csic.es

Conclusions

Development of CPW on cyclic olefin TOPAS copolymer is realized, a novel technique

is used in order to develop thin films TOPAS that was used as a CPW substrate;

electrical characterization shows that TOPAS is a good contender to develop

inexpensive Terahertz technology, a survey with an FTIR remains to be done on the thin

films to obtain the electrical response (dielectric function) in higher range of

frequency (0.1- 6 THz) to corroborate our results. TOPAS shows good compatibility with

most popular microfabrication technics including dry and wet etching process

Acknowledgements

Financial support from CONACYT for the stay at IMM-CSIC of IMDA and ELH is gratefully acknowledged

We gratefully acknowledge GaAs heterostructure growth from the MBE group @I MM for Schotkky diode fabrication

We also acknowledge technical help in the fabrication of the optical masks by Manuel Rodriguez from IMDEA Nanociencia @ Madrid, Spain.

PC and JLCK acknowledge financial support form the project S2013/ICE-2822 Space-TEC CM from the “Comunidad de Madrid”

Recent advances in the fabrication of Cyclic-Olefin Copolymer,TOPAS based THz Coplanar Waveguides (CPW) are described. Firstly the TOPAS films are fabricated by dissolving the raw material in toluene at

different concentrations and by subsequent deposition on top of Silicon wafer substrates. We found the best homogeneity and roughness results for the films where the solvent is extracted by vacuum

desorption on top of the wafer and then hot embossed. Metal patterns are then designed and fabricated on top of the TOPAS film by conventional optical lithography and wet etching. The metal is 2nm Cr + 200

nm gold. The expected electrical characteristics in the frequency range of interest are calculated and extrapolated from a quasistatic regimen.

[1] B. Ferguson X. Zhang “Materials for terahertz science and technology” Nature Materials, Vol. 1, Sep 2002.

[2] S. Atakaramians, S. Afshar, T. M. Monro, D. Abbott “Terahertz Dielectric Waveguides” Advance in Optics and Photonics, Vol. 5, Pag. 169-215, 2013.

[3] I. Akyildiz, J. Miquel, C. Han “Terahertz band: Next frontier for wireless communications” Physical Communications, Vol. 12, Pag. 16-32, 2014.

2 TOPAS film fabrication

Chattopadhyay “Technology, Capabilities,

and Performance of Low Power Terahertz

Sources” IEEE Trans. On THz, Sci. and

Tec. Sep 2011

Frequency tripler @ 2,7 THz

L. M. Diaz et al J. of Infrared

Millimeter And THz Waves

(2016)

1 Motivation

3CPW fabrication with TOPAS film

2 cm

Mask Fabrication using maskless lithography*

@ IMDEA *DW 2000 Heidelberg laser pattern generator

http://www.topas.com/products/topas-coc-polymers

Three different TOPAS in Toluene concentrations :

10% de TOPAS, 9.6 gr en 100 ml “T10%/t”

20% de TOPAS, 21.75 gr en 100 ml “T20%/t”

30% de TOPAS, 37.28 gr en 100 ml “T30%/t”

Spin Coating in three different substrates

Doped Si P <100>

Doped Si P <100> treated with HF

500 nm Si3N4 on Si

Two approaches: Dissolve TOPAS in Toluene and

1) Spin coating, vacuum desorption and hot embossing

2) Solvent evaporation by oven annealing

Before Spin

Coating (SC) After SC

sample

Topas

film

scan 1

scan 2

0

100

200

300

400

500

0 5000 10000 15000 20000 25000

scan 1

scan 2

m

m

0

50

100

150

200

0 5000 10000 15000 20000

scan 1

scan 2

m

m

sample

Topas

film

notch

0

50

100

150

200

0 6000 12000

scan 1

scan 2

scan 3

scan 4

scan 5

scan 6

m

m

M1

M2

M3

M4

0

1

2

3

4

0

1

2

3

4

5

0 0.5 1 1.5

Re()

Im()

f (THz)

Optical characterization

Sample code Thickness

(mm) Volume

(mL) TOPAS %

Dissolution

M1 49 0.10 10

M2 78 0.15 10

Sample code Thickness

(mm) Spin speed

(rpm) Final cure

(°C/minute)

M3 97 3000 120/7

M4 123 3000 120/7

Thin Au or CrAu film deposition, conventional litography

and wet etching @ IMM

Profiles before

and after hot

embossing

Groove profiles

60

80

100

120

140

160

0 2 4 6 8 10 12 14

H =165 m

H =160 m

H =127 m

H = 100 m

H = 50 m

H = 30 m

H = 10 m

H = 5 m

Z0(

)

W(m)

Impedance characteristic (Z0) as a function of W its

calculation is performed for different values of H.

4 Calculated impedance of the CPW

Espectrógrafo (Terahertz o FTIR)

Muestra de polímero

Función dieléctrica

Longitud de onda (mm).

Modelado electromagnético

Guía de onda coplanar

Dimensiones y materiales óptimos para la

realización de guías de ondas entre los 0.1

y 3 Terahertz

Tierra

Collaboration project with IPN México to develop both THz CPW technology and also Schotkky diodes (not shown)

Terahertz regimen (0.1-10 THz) represents de gap between microwaves and far-infrared spectrum which was mainly used for passive detections in

astronomical applications, however with the emergence of low power terahertz sources using former microwave source methods such as harmonic

oscillators and frequency multipliers, femtoseconds lasers and photoconductive antennas give rise to a large number of applications as terahertz

spectroscopy systems for material characterizations, imaging systems, biomaterial applications, and sensing applications [1-2]…. moreover Akyildiz

et al carry [3] out and in-depth study about potential applications in higher speed wireless communication

Graphic summary of project The polymer: TOPAS®