18-08-2012, 12:51 PM
LIQUID CRYSTAL POLYMER IN MEMS APPLICATIONS
[attachment=32020]
INTRODUCTION
MEMS field evolved from the semiconductor industry
Initially,silicon had been the predominant material
Emergence of polymers in MEMS industry due to:
(i) Lower cost
(ii) Flexible fabrication & packaging techniques
(iii) Unique physical & chemical properties such as
biocompatibilty & high mechanical fracture limit
LIQUID CRYSTAL POLYMER(LCP)
Molecules mutually aligned & organised (as in a crystal)
Bulk of LCP can flow in molten state(as in a liquid)
Rigid flexible monomers that align in shear flow direction
Persistence of orientation even below melting point
temperature
LCP PROPERTIES
•Barrier to gases like O2,N2,CO2
•Good chemical resistance
•Flexible & capable of multilayer
lamination
•Low coefficient of hygroscopic
expansion
•Mechanical properties are
anisotropic and dependent on
polymer orientation
•Low temperature thermal
bonding
•Biocompatibility
MICROFABRICATION TECHNIQUES
•OXYGEN PLASMA REACTIVE ION ETCHING
Deposition & patterning of Al on LCP film
Partial oxygen plasma etch of LCP
Second patterning of Al etch mask
Plasma etch through LCP leaving a flap
Removal of Al mask
Fabrication of a suspended flap supported by cantilevers
SEM micrograph showing a flat flap supported by two
fixed-free beams in the LCP film.
(Etch rate of 25 μm /min at 500 mTorr)
•LAMINATION PROCESS USING SURFACE ACTIVATED
BONDING
Lamination of Cu foil & LCP film
Sputter cleaning of Cu & LCP surfaces with argon radio
frequency plasma etching in vacuum
Removal of inactive layers of native oxide and contaminants
achieved
Deposition of Cu on the LCP film followed by direct bonding
at room temperature
Subsequent heating of Cu/LCP sample for better interface
adhesion
Bonded interface 15 times smoother than that produced by
heated lamination method
[attachment=32020]
INTRODUCTION
MEMS field evolved from the semiconductor industry
Initially,silicon had been the predominant material
Emergence of polymers in MEMS industry due to:
(i) Lower cost
(ii) Flexible fabrication & packaging techniques
(iii) Unique physical & chemical properties such as
biocompatibilty & high mechanical fracture limit
LIQUID CRYSTAL POLYMER(LCP)
Molecules mutually aligned & organised (as in a crystal)
Bulk of LCP can flow in molten state(as in a liquid)
Rigid flexible monomers that align in shear flow direction
Persistence of orientation even below melting point
temperature
LCP PROPERTIES
•Barrier to gases like O2,N2,CO2
•Good chemical resistance
•Flexible & capable of multilayer
lamination
•Low coefficient of hygroscopic
expansion
•Mechanical properties are
anisotropic and dependent on
polymer orientation
•Low temperature thermal
bonding
•Biocompatibility
MICROFABRICATION TECHNIQUES
•OXYGEN PLASMA REACTIVE ION ETCHING
Deposition & patterning of Al on LCP film
Partial oxygen plasma etch of LCP
Second patterning of Al etch mask
Plasma etch through LCP leaving a flap
Removal of Al mask
Fabrication of a suspended flap supported by cantilevers
SEM micrograph showing a flat flap supported by two
fixed-free beams in the LCP film.
(Etch rate of 25 μm /min at 500 mTorr)
•LAMINATION PROCESS USING SURFACE ACTIVATED
BONDING
Lamination of Cu foil & LCP film
Sputter cleaning of Cu & LCP surfaces with argon radio
frequency plasma etching in vacuum
Removal of inactive layers of native oxide and contaminants
achieved
Deposition of Cu on the LCP film followed by direct bonding
at room temperature
Subsequent heating of Cu/LCP sample for better interface
adhesion
Bonded interface 15 times smoother than that produced by
heated lamination method