Transcript Research Activities at INTEC

WAVEGUIDES IN BOARDS
BASED ON ORMOCERs
[email protected]
IMEC - INTEC
Department of Information Technology
http://www.intec.ugent.be
Outline







Introduction
ORMOCERs
Laser ablation
Waveguides
Deflecting optics
Coupling structure
Conclusion
INTEC - Department of Information Technology
Introduction


Integration of optical interconnects on board level
Approaches


Fiber based
Waveguide based
 glass sheet
 polymers
http://www.circuitree.com
Printed Optical Waveguides: The Next Interconnect (H.Holden)
INTEC - Department of Information Technology
ORMOCERs

ORganic Modified CERamics




Fraunhofer Institute - Germany
Inorganic-Organic Hybrid Polymers
Applications
 microoptical elements (lenses, lens arrays, gratings, prisms)
 vertical integration: stacked optical waveguides (wafer scale)
 board level optical interconnects
General properties





Compatibility with PCB manufacturing
 lamination 180°C 200 Pascals
 assembly (solder reflow) up to 250°C
Good planarisation properties
RMS roughness 2 - 4 nm
Long-term stability under variable environmental conditions
(humidity, temperature)
Low shrinkage
INTEC - Department of Information Technology
ORMOCERs

Optical properties (www.microresist.de)



Refractive index @ 830 nm (adjustable)
 CORE 1.5475
 CLADDING 1.5306
Attenuation
Waveguides


Photolithography
Laser ablation
INTEC - Department of Information Technology
ORMOCERs

Application scheme
flood exposure
application
spin-coating
softbake
80-120 °C, <5 min
exposure
laser ablation
curing
120-240 °C, up to 3 hrs
INTEC - Department of Information Technology
post exposure bake
80-120 °C, <5 min
curing
120-240 °C, up to 3 hrs
development
Laser ablation

Set-up
KrF Excimer Laser
(can be tilted)
248 nm
INTEC - Department of Information Technology
Frequency tripled
Nd-YAG Laser
355 nm
CO2 Laser
9.6 m
Waveguides

UV-Defined

Cross section: 20 x 20 μm2 waveguides (250 μm pitch)
OPTICAL LAYERS
COPPER
FR4

Laser-ablated





Compatible with standard electrical PCB manufacturing (microvia’s)
Adapt the pattern as a function of distortion in the substrate (FR4)
Rapid prototyping
Define microstructures and microoptics on a top surface of a
heterogeneous optoelectronic module in a very late phase of the
assembly process
Entire optical interconnection using one technology
INTEC - Department of Information Technology
Waveguides

Laser-ablated




Laser beam moves over surface
Technology sequence
 bottom cladding layer
 core layer
 laser ablation microstructuring
 upper cladding layer
Experimental results
KrF Excimer laser (248 nm)




50 x 50 μm2
trapezoidal shape
low ablation speed
roughness to high
INTEC - Department of Information Technology
1st ablation
2nd ablation
Waveguides

Frequency tripled Nd-YAG laser (355 nm)





50 x 50 μm2
clean surfaces
ablation speed: 1 mm/s
photo-dissociation
photo-thermal ablation
INTEC - Department of Information Technology
Deflecting optics

45 micromirrors

micro machining techniques (90 V-shaped diamond blade)
 excellent cut surface
 difficult to cut individual waveguides on the same substrate
(physical size of the machining tool)
diamond blade
cladding
core
cladding
substrate

remove waveguide film from substrate

cutting from back-side
INTEC - Department of Information Technology
Deflecting optics

45 micromirrors

RIE
reactive ion etching RIE (45 oblique etching)
 limited by directional freedom
 different process steps
Al mask
cladding
core
cladding
substrate

temperature controlled RIE (90 RIE + heat treatment)
 not limited by directional freedom
 material dependent

laser ablation
 set-up: excimer laser beam can be tilted
– Total Internal Reflection (TIR)
negative facet
– coated mirror (Al, Au)
positive facet
INTEC - Department of Information Technology
TIR condition crucial
glue (mounting lens plate)
humidity
Deflecting optics

Total Internal Reflection



Smooth surface
Tapering compensated
Flatness of the mirror at core layer
INTEC - Department of Information Technology
Coupling structure

Example: MT-compatible coupling

Microlenses and 700 m holes
ablated in a polycarbonate (PC) plate
(Kris Naessens, Ph.D. thesis Ghent University)



Alignment: ribbon - lenses:
700 m pins match holes in PC plate
Alignment: micromirror - lenses:
flip chip set-up (alignment marks)
Lenses ablated in upper-cladding layer

Visual alignment under ablation set-up
with respect to 45 micromirror
INTEC - Department of Information Technology
Conclusion

Integration of optical interconnects on board level


Compatibility with the manufacturing and assembly processes
of the conventional electrical board technology



ORMOCERs
Laser ablation
Entire optical interconnection using one technology





polymer waveguides
Waveguides
Micromirrors
Microlenses
Alignment features
SEM pictures show very smooth surfaces
INTEC - Department of Information Technology